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  • 1.
    Andersson, Eva A
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Grundström, Helen
    Thorstensson, Alf
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Diverging intramuscular activity patterns in back and abdominal muscles during trunk rotation.2002In: Spine, ISSN 1528-1159, Vol. 27, no 6, p. E152-60Article in journal (Refereed)
    Abstract [en]

    STUDY DESIGN: An intramuscular electromyographic study was performed on trunk rotations during sitting and standing. OBJECTIVE: The aim was to provide new information on activation levels for deep trunk muscles in various unresisted and resisted trunk rotations. SUMMARY AND BACKGROUND DATA: Frequent daily trunk twisting and decreased maximal strength during trunk rotation have been associated with low back pain or sciatic pain. However, the involvement of deep trunk muscles during different trunk rotations is relatively unknown. METHODS: Ten healthy subjects participated. Fine-wire electrodes were inserted, under ultrasound guidance, into psoas, quadratus lumborum, the superficial medial lumbar erector spinae (ES-s, multifidus) and its deep lateral portion (ES-d, iliocostalis), iliacus, rectus abdominis, obliquus externus, and obliquus internus. RESULTS: The highest involvement for all muscles was observed on the ipsilateral side, in maximal trunk twists with shoulder resistance, except obliquus externus, which showed a dominant contralateral side, and rectus abdominis, which was little activated in all rotations. In contrast, maximal trunk twist without shoulder resistance, i.e., freely performed, resulted generally in lower levels for all muscles involved and in a shift of side dominance for the lumbar muscles quadratus lumborum, psoas, and ES-s. CONCLUSIONS: During trunk rotations the activity patterns for various trunk muscles could drastically change, and even be the opposite, between the two body sides, within the same type of task, depending on several factors such as initial position, effort level, sitting or standing, and external shoulder resistance.

  • 2.
    Andersson, Eva A
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Ma, Z
    Thorstensson, Alf
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Relative EMG levels in training exercises for abdominal and hip flexor muscles.1998In: Scandinavian Journal of Rehabilitation Medicine, ISSN 0036-5505, E-ISSN 1940-2228, Vol. 30, no 3, p. 175-83Article in journal (Refereed)
    Abstract [en]

    The main purpose of our study was to compare systematically EMG levels in sub-maximal training exercises for the trunk and hip flexor muscles with those voluntarily attainable in corresponding situations. Six healthy subjects performed three types of standardized training exercises, whose static positions, movement velocity and range of motion were reproduced during maximal voluntary isokinetic strength tests. EMG was recorded with wire electrodes from the iliacus muscle and with surface electrodes from the rectus femoris, sartorius, rectus abdominis, obliquus externus and internus muscles. The relative EMG values demonstrated a task dependency which could differ between individual muscles. The maximal voluntary activation levels were relatively constant across conditions. Exceptions were present, particularly for the rectus femoris and iliacus muscles. These findings highlight the consequences of using different methods of normalizing EMG. The relative EMG values presented may serve as guidelines when selecting training exercises for specific trunk and hip flexor muscles in sports and rehabilitation.

  • 3.
    Andersson, Eva A
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Nilsson, Johnny
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Ma, Z
    Thorstensson, Alf
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Abdominal and hip flexor muscle activation during various training exercises.1997In: European Journal of Applied Physiology and Occupational Physiology, ISSN 0301-5548, E-ISSN 1432-1025, Vol. 75, no 2, p. 115-23Article in journal (Refereed)
    Abstract [en]

    The purpose of this study was to provide objective information on the involvement of different abdominal and hip flexor muscles during various types of common training exercises used in rehabilitation and sport. Six healthy male subjects performed altogether 38 different static and dynamic training exercises trunk and hip flexion sit-ups, with various combinations of leg position and support, and bi- and unilateral leg lifts. Myoelectric activity was recorded with surface electrodes from the rectus abdominis, obliquus externus, obliquus internus, rectus femoris, and sartorius muscles and with indwelling fine-wire electrodes from the iliacus muscle. The mean electromyogram amplitude, normalised to the highest observed value, was compared between static and dynamic exercises separately. The hip flexors were highly activated only in exercises involving hip flexion, either lifting the whole upper body or the legs. In contrast, the abdominal muscles showed marked activation both during trunk and hip flexion sit-ups. In hip flexion sit-ups, flexed and supported legs increased hip flexor activation, whereas such modifications did not generally alter the activation level of the abdominals. Bilateral, but not unilateral, leg lifts required activation of abdominal muscles. In trunk flexion sit-ups an increased activation of the abdominal muscles was observed with increased flexion angle, whereas the opposite was true for hip flexion sit-ups. Bilateral leg lifts resulted in higher activity levels than hip flexion sit-ups for the iliacus and sartorius muscles, while the opposite was true for rectus femoris muscles. These data could serve as a basis for improving the design and specificity of test and training exercises.

  • 4.
    Andersson, Eva A
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Nilsson, Johnny
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Thorstensson, Alf
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Intramuscular EMG from the hip flexor muscles during human locomotion.1997In: Acta Physiologica Scandinavica, ISSN 0001-6772, E-ISSN 1365-201X, Vol. 161, no 3, p. 361-70Article in journal (Refereed)
    Abstract [en]

    The purpose was to investigate the activation pattern of five major hip flexor muscles and its adaptation to changing speed and mode of progression. A total of 11 healthy subjects performed walking and running on a motor-driven treadmill at speeds ranging from 1.0 to 6.0 m s-1. Intramuscular fine-wire electrodes were used to record myoelectric signals from the iliacus, psoas, sartorius, rectus femoris and tensor fascia latae muscles. The basic pattern, with respect to number of activation periods, remained the same irrespective of speed and mode of progression. However, differences in the relative duration and timing of onset of activation occurred between individual muscles. Over the speed range in walking, a progressively earlier onset was generally seen for the activation period related to hip flexion. Changes in EMG amplitude were measured in the iliacus and psoas muscles and showed a marked increase and difference between walking and running at speeds above 2.0 m s-1. Thus, the alternating flexion-extension movements at the hip during locomotion appear to be governed by a rather fixed 'neural program' which normally only needs minor modulations to accomplish the adjustments accompanying an increase in speed of progression as well as a change from walking to running.

  • 5.
    Andersson, Eva A
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Thorstensson, Alf
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Utvärdering av träningsövningar för buk- och höftmuskulaturen.1993In: Arbetsmiljöfondens Sammanfattningar, no 1563, p. 1-8Article, review/survey (Other academic)
  • 6.
    Andersson, Eva
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Oddsson, L
    Grundström, H
    Nilsson, Johnny
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Thorstensson, Alf
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    EMG activities of the quadratus lumborum and erector spinae muscles during flexion-relaxation and other motor tasks.1996In: Clinical biomechanics (Bristol, Avon), Vol. 11, no 7, p. 392-400Article in journal (Refereed)
    Abstract [en]

    OBJECTIVE: The aim of this study was to provide new information on the myoelectrical activation of the quadratus lumborum, the deep lateral and the superficial medial lumbar erector spinae, the psoas, and the iliacus muscles in various motor tasks. DESIGN: An intramuscular electromyographic study was performed. BACKGROUND: The contribution of individual deep trunk muscles to the stability of the lumbar spine is relatively unknown in different tasks, including the flexion-relaxation phenomenon. METHODS: Seven healthy subjects participated. Fine-wire electrodes were inserted with a needle guided by ultrasound. RESULTS: The highest activity observed for quadratus lumborum and deep lateral erector spinae occurred in ipsilateral trunk flexion in a side-lying position and for superficial medial erector spinae during bilateral leg lift in a prone position. Quadratus lumborum and deep lateral erector spinae were activated when the flexion-relaxation phenomenon was present for superficial medial erector spinae, i.e. when its activity ceased in the latter part of full forward flexion of the trunk, held relaxed and kyphotic. CONCLUSIONS: In general, the activation of the investigated muscles showed a high degree of task specificity, where activation of a certain muscle was not always predictable from its anatomical arrangement and mechanical advantage.

  • 7.
    Andersson, Eva
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Oddsson, L
    Grundström, H
    Thorstensson, Alf
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    The role of the psoas and iliacus muscles for stability and movement of the lumbar spine, pelvis and hip.1995In: Scandinavian Journal of Medicine and Science in Sports, ISSN 0905-7188, E-ISSN 1600-0838, Vol. 5, no 1, p. 10-6Article in journal (Refereed)
    Abstract [en]

    The activation patterns of the psoas and iliacus muscles were investigated in 7 healthy adult subjects (4 men and 3 women) during a variety of motor tasks in standing, sitting and lying. Myoelectric activity was recorded simultaneously from the 2 muscles using thin wire electrodes inserted under guidance of high-resolution ultrasound. In general, both muscles were coactivated, albeit to different relative levels, particularly when hip flexor torque was required. Selective activation of the iliacus could, however, be seen to stabilize the pelvis in contralateral hip extension during standing. Psoas was found to be selectively involved in sitting with a straight back and in contralateral loading situations requiring stabilization of the spine in the frontal plane. During training exercises from a supine position, such as sit-ups, the contribution of the psoas and iliacus muscles could be varied by changing the range of motion as well as the position and support for the legs. Thus, the 2 anatomically different muscles of the iliopsoas complex were shown to have individual and task-specific activation patterns depending on the particular demands for stability and movement at the lumbar spine, pelvis and hip.

  • 8.
    Andersson, Eva
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Swärd, L
    Thorstensson, Alf
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Trunk muscle strength in athletes.1988In: Medicine & Science in Sports & Exercise, ISSN 0195-9131, E-ISSN 1530-0315, Vol. 20, no 6, p. 587-93Article in journal (Refereed)
    Abstract [en]

    Maximal voluntary strength of the trunk muscles was measured in 57 male elite athletes (soccer players, wrestlers, tennis players, and gymnasts), 14 female elite gymnasts, and in a normal group of 87 conscripts. Mean ages in the different groups ranged from 18-22 yr. An isokinetic (constant velocity) technique was used to record maximal torque produced by trunk and hip muscles during flexion, extension, and lateral flexion over the range of motion. The constant angular velocities used were 15 deg.s-1 and 30 deg.s-1, respectively. Isometric strength was measured in a straight body position (0 deg. of flexion). The measurements were made with the subjects in a horizontal position with the pivot point at the hip and at the lumbar (L2-L3) level. All male athlete groups showed higher peak torque values than the normals. The differences were largest in hip extension and trunk flexion. The male gymnasts also showed significantly higher peak values in hip flexion as compared to all other categories. There was no difference in strength per kg body weight between female gymnasts and untrained males, except in trunk extension. The position for peak torque occurred earlier in the movements for the athletes, especially for the gymnasts in extension movements and for the tennis players in flexion movements. In isometric contractions essentially the same strength differences were present as in the slow isokinetic contractions. In lateral flexion wrestlers and tennis players showed significantly higher strength in movements toward the nondominant side. Thus, differences were present between the athletes and the normals, some of which appeared to be sport specific and related to long-term systematic training.(ABSTRACT TRUNCATED AT 250 WORDS)

  • 9.
    Arndt, Anton
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Bengtsson, Ann-Sophie
    Peolsson, Michael
    Thorstensson, Alf
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Movin, Tomas
    Non-uniform displacement within the Achilles tendon durig passive ankle joint motion.2012In: Knee Surgery, Sports Traumatology, Arthroscopy, ISSN 0942-2056, E-ISSN 1433-7347, Vol. 20, no 9, p. 1868-74Article in journal (Refereed)
    Abstract [en]

    PURPOSE:

    An initial step in the understanding of Achilles tendon dynamics is to investigate the effects of passive motion, thereby minimising muscle activation and reducing internal joint forces. Internal tendon dynamics during passive ankle joint motion have direct implications for clinical rehabilitation protocols after Achilles tendon surgery. The aim of this study was to test the hypothesis that tendon tissue displacement is different in different layers of the Achilles tendon during controlled passive ankle joint movements.

    METHODS:

    Ultrasound imaging was conducted on the right Achilles tendon of nine healthy recreationally active males. Standardised isokinetic passive dorsi-plantar-flexion movements were performed with a total range of motion of 35°. The tendon was divided into superficial, central and deep layers in the resulting B-mode ultrasound images viewed in the sagittal plane. A block-matching speckle tracking algorithm was applied post-process, with kernels for the measurement of displacement placed in each of the layers.

    RESULTS:

    The mean (SD) displacement of the Achilles tendon during passive dorsiflexion was 8.4 (1.9) mm in the superficial layer, 9.4 (1.9) mm in the central portion and 10.4 (2.1) mm in the deep layer, respectively. In all cases, the movement of the deep layer of the tendon was greater than that of the superficial one (P < 0.01).

    CONCLUSIONS:

    These results, achieved in vivo with ultrasonographic speckle tracking, indicated complex dynamic differences in different layers of the Achilles tendon, which could have implications for the understanding of healing processes of tendon pathologies and also of normal tendon function.

  • 10.
    Askling, Carl
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Karlsson, J
    Thorstensson, Alf
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Hamstring injury occurrence in elite soccer players after preseason strength training with eccentric overload.2003In: Scandinavian Journal of Medicine and Science in Sports, ISSN 0905-7188, E-ISSN 1600-0838, Vol. 13, no 4, p. 244-50Article in journal (Refereed)
    Abstract [en]

    The primary purpose of this study was to evaluate whether a preseason strength training programme for the hamstring muscle group - emphasising eccentric overloading - could affect the occurrence and severity of hamstring injuries during the subsequent competition season in elite male soccer players. Thirty players from two of the best premier-league division teams in Sweden were divided into two groups; one group received additional specific hamstring training, whereas the other did not. The extra training was performed 1-2 times a week for 10 weeks by using a special device aiming at specific eccentric overloading of the hamstrings. Isokinetic hamstring strength and maximal running speed were measured in both groups before and after the training period and all hamstring injuries were registered during the total observational period of 10 months. The results showed that the occurrence of hamstring strain injuries was clearly lower in the training group (3/15) than in the control group (10/15). In addition, there were significant increases in strength and speed in the training group. However, there were no obvious coupling between performance parameters and injury occurrence. These results indicate that addition of specific preseason strength training for the hamstrings - including eccentric overloading - would be beneficial for elite soccer players, both from an injury prevention and from performance enhancement point of view.

  • 11.
    Askling, Carl
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Lund, H
    Saartok, T
    Thorstensson, Alf
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Self-reported hamstring injuries in student-dancers.2002In: Scandinavian Journal of Medicine and Science in Sports, ISSN 0905-7188, E-ISSN 1600-0838, Vol. 12, no 4, p. 230-5Article in journal (Refereed)
    Abstract [en]

    Dancing involves powerful movements as well as flexibility exercises, both of which may be related to specific injuries to the musculo-tendinosus tissue, e.g., the hamstring muscle complex. In this study, the occurrence of acute and overuse injuries to the rear thigh in dancers was investigated retrospectively by means of a questionnaire. All but one (n = 98) of the student-dancers (age 17-25 years) at the Ballet Academy in Stockholm participated. The results demonstrated that, during the past 10 years, every third dancer (34%) reported that they had acute injuries and every sixth dancer (17%) had overuse injuries to the rear thigh. Most (91%) of the acute injuries were subjectively located to an area close to tuber ischiadicum. The majority (88%) stated that the acute injury occurred during slow activities in flexibility training, e.g., splits, and only a few (12%) in powerful movements. Continuing problems were reported by 70% of the acutely injured dancers. Many of the dancers neglected their acute injury (14 did not even stop the ongoing dance activity) and they also greatly underestimated the recovery time. Only 4 dancers (12%) received acute medical assistance. Thus the results, based on the recollection of the subjects, indicated that stretching could induce severe strain injuries to the proximal hamstrings in dancers. Extrapolating these results to the practice, it can be recommended that stretching exercises be executed with caution in connection with dancing sessions and training, and that, information about the seriousness and acute treatment of such injuries be added to the student-dancers' curriculum.

  • 12.
    Askling, Carl M
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Tengvar, Magnus
    Saartok, Tönu
    Thorstensson, Alf
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Acute first-time hamstring strains during high-speed running: a longitudinal study including clinical and magnetic resonance imaging findings.2007In: American Journal of Sports Medicine, ISSN 0363-5465, E-ISSN 1552-3365, Vol. 35, no 2, p. 197-206Article in journal (Refereed)
    Abstract [en]

    BACKGROUND: Hamstring muscle strain is one of the most common injuries in sports. Still, knowledge is limited about the progression of clinical and magnetic resonance imaging characteristics and their association with recovery time in athletes. HYPOTHESIS: Knowing the anatomical location and extent of an acute first-time hamstring strain in athletes is critical for the prognosis of recovery time. STUDY DESIGN: Case series (prognosis); Level of evidence, 2. METHODS: Eighteen elite sprinters with acute first-time hamstring strains were prospectively included in the study. All subjects were examined, clinically and with magnetic resonance imaging, on 4 occasions after injury: at day 2 to 4, 10, 21, and 42. The clinical follow-up period was 2 years. RESULTS: All sprinters were injured during competitive sprinting, and the primary injuries were all located in the long head of the biceps femoris muscle. There was an association between the time to return to pre-injury level (median, 16; range, 6-50 weeks) and the extent of the injury, as indicated by the magnetic resonance imaging parameters. Involvement of the proximal free tendon, as estimated by MRI, and proximity to the ischial tuberosity, as estimated both by palpation and magnetic resonance imaging, were associated with longer time to return to pre-injury level. CONCLUSION: Careful palpation during the first 3 weeks after injury and magnetic resonance imaging investigation performed during the first 6 weeks after injury provide valuable information that can be used to predict the time to return to pre-injury level of performance in elite sprinting.

  • 13.
    Askling, Carl M
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Tengvar, Magnus
    Saartok, Tönu
    Thorstensson, Alf
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Acute first-time hamstring strains during slow-speed stretching: clinical, magnetic resonance imaging, and recovery characteristics.2007In: The American journal of sports medicine, ISSN 1552-3365, Vol. 35, no 10, p. 1716-24Article in journal (Refereed)
    Abstract [en]

    BACKGROUND: Hamstring strains can be of 2 types with different injury mechanisms, 1 occurring during high-speed running and the other during stretching exercises. HYPOTHESIS: A stretching type of injury to the proximal rear thigh may involve specific muscle-tendon structures that could affect recovery time. STUDY DESIGN: Case series (prognosis); Level of evidence, 2. METHODS: Fifteen professional dancers with acute first-time hamstring strains were prospectively included in the study. All subjects were examined, clinically and with magnetic resonance imaging, on 4 occasions after injury: at day 2 to 4, 10, 21, and 42. The clinical follow-up period was 2 years. RESULTS: All dancers were injured during slow hip-flexion movements with extended knee and experienced relatively mild acute symptoms. All injuries were located proximally in the posterior thigh close to the ischial tuberosity. The injury involved the semimembranosus (87%), quadratus femoris (87%), and adductor magnus (33%). All injuries to the semimembranosus involved its proximal free tendon. There were no significant correlations between clinical or magnetic resonance imaging parameters and the time to return to preinjury level (median, 50 weeks; range, 30-76 weeks). CONCLUSION: Stretching exercises can give rise to a specific type of strain injury to the posterior thigh. A precise history and careful palpation provide the clinician enough information to predict a prolonged time until return to preinjury level. One factor underlying prolonged recovery time could be the involvement of the free tendon of the semimembranosus muscle.

  • 14.
    Askling, Carl M
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Tengvar, Magnus
    Saartok, Tönu
    Thorstensson, Alf
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Proximal hamstring strains of stretching type in different sports: injury situations, clinical and magnetic resonance imaging characteristics, and return to sport.2008In: The American journal of sports medicine, ISSN 1552-3365, Vol. 36, no 9, p. 1799-804Article in journal (Refereed)
    Abstract [en]

    BACKGROUND: Hamstring strains can be of at least 2 types, 1 occurring during high-speed running and the other during motions in which the hamstring muscles reach extreme lengths, as documented for sprinters and dancers. HYPOTHESIS: Hamstring strains in different sports, with similar injury situations to dancers, also show similarities in symptoms, injury location, and recovery time. STUDY DESIGN: Case series (prognosis); Level of evidence, 4. METHODS: Thirty subjects from 21 different sports were prospectively included. All subjects were examined clinically and with magnetic resonance imaging (MRI). The follow-up period lasted until the subjects returned to or finished their sport activity. RESULTS: All injuries occurred during movements reaching a position with combined extensive hip flexion and knee extension. They were located proximally in the posterior thigh, close to the ischial tuberosity. The injuries were often complex, but 83% involved the semimembranosus and its proximal free tendon. Fourteen subjects (47%) decided to end their sports activity. For the remaining 16 subjects, the median time for return to sport was 31 weeks (range, 9-104). There were no significant correlations between specific clinical or MRI parameters and time to return to sport. CONCLUSIONS: In different sports, an injury situation in which the hamstring muscles reach extensive length causes a specific injury to the proximal posterior thigh, earlier described in dancers. Because of the prolonged recovery time associated with this type of injury, correct diagnosis, based on history and palpation, and adequate information to the subject are essential.

  • 15.
    Askling, Carl M
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Tengvar, Magnus
    Tarassova, Olga
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Thorstensson, Alf
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Acute hamstring injuries in Swedish elite sprinters and jumpers: a prospective randomised controlled clinical trial comparing two rehabilitation protocols.2014In: British Journal of Sports Medicine, ISSN 0306-3674, E-ISSN 1473-0480, Vol. 48, no 7, p. 532-9Article in journal (Refereed)
    Abstract [en]

    BACKGROUND: Hamstring strain is a common injury in sprinters and jumpers, and therefore time to return to sport and secondary prevention become of particular concern.

    OBJECTIVE: To compare the effectiveness of two rehabilitation protocols after acute hamstring injury in Swedish elite sprinters and jumpers by evaluating time needed to return to full participation in the training process.

    STUDY DESIGN: Prospective randomised comparison of two rehabilitation protocols.

    METHODS: Fifty-six Swedish elite sprinters and jumpers with acute hamstring injury, verified by MRI, were randomly assigned to one of two rehabilitation protocols. Twenty-eight athletes were assigned to a protocol emphasising lengthening exercises, L-protocol, and 28 athletes to a protocol consisting of conventional exercises, C-protocol. The outcome measure was the number of days to return to full training. Re-injuries were registered during a period of 12 months after return.

    RESULTS: Time to return was significantly shorter for the athletes in the L-protocol, mean 49 days (1SD±26, range 18-107 days), compared with the C-protocol, mean 86 days (1SD±34, range 26-140 days). Irrespective of protocol, hamstring injuries where the proximal free tendon was involved took a significantly longer time to return than injuries that did not involve the free tendon, L-protocol: mean 73 vs 31 days and C-protocol: mean 116 vs 63 days, respectively. Two reinjuries were registered, both in the C-protocol.

    CONCLUSIONS: A rehabilitation protocol emphasising lengthening type of exercises is more effective than a protocol containing conventional exercises in promoting time to return in Swedish elite sprinters and jumpers.

  • 16.
    Askling, Carl M
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Tengvar, Magnus
    Thorstensson, Alf
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Acute hamstring injuries in Swedish elite football: a prospective randomised controlled clinical trial comparing two rehabilitation protocols.2013In: British Journal of Sports Medicine, ISSN 0306-3674, E-ISSN 1473-0480, Vol. 47, no 15, p. 953-9Article in journal (Refereed)
    Abstract [en]

    BACKGROUND: Hamstring injury is the single most common injury in European professional football and, therefore, time to return and secondary prevention are of particular concern.

    OBJECTIVE: To compare the effectiveness of two rehabilitation protocols after acute hamstring injury in Swedish elite football players by evaluating time needed to return to full participation in football team-training and availability for match selection.

    STUDY DESIGN: Prospective randomised comparison of two rehabilitation protocols.

    METHODS: Seventy-five football players with an acute hamstring injury, verified by MRI, were randomly assigned to one of two rehabilitation protocols. Thirty-seven players were assigned to a protocol emphasising lengthening exercises, L-protocol and 38 players to a protocol consisting of conventional exercises, C-protocol. The outcome measure was the number of days to return to full-team training and availability for match selection. Reinjuries were registered during a period of 12 months after return.

    RESULTS: Time to return was significantly shorter for the players in the L-protocol, mean 28 days (1SD±15, range 8-58 days), compared with the C-protocol, mean 51 days (1SD±21, range 12-94 days). Irrespective of protocol, stretching-type of hamstring injury took significantly longer time to return than sprinting-type, L-protocol: mean 43 vs 23 days and C-protocol: mean 74 vs 41 days, respectively. The L-protocol was significantly more effective than the C-protocol in both injury types. One reinjury was registered, in the C-protocol.

    CONCLUSIONS: A rehabilitation protocol emphasising lengthening type of exercises is more effective than a protocol containing conventional exercises in promoting time to return in Swedish elite football.

  • 17.
    Askling, Carl
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Nilsson, Johnny
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Thorstensson, Alf
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    A new hamstring test to complement the common clinical examination before return to sport after injury2010In: Knee Surgery, Sports Traumatology, Arthroscopy, ISSN 0942-2056, E-ISSN 1433-7347, Vol. 18, no 12, p. 1788-1803Article in journal (Refereed)
    Abstract [en]

    PURPOSE: The aim was to introduce and evaluate the reliability and validity of an active hamstring flexibility test as a complement to common clinical examination when determining safe return to sport after hamstring injury.

    METHODS: Eleven healthy subjects (28 years) were tested on repeated occasions, and 11 athletes (21 years) with MRI-verified acute hamstring strain were tested when common clinical examination revealed no signs of remaining injury, i.e. there was no differences between the legs in palpation pain, manual strength tests, and passive straight leg raise. Flexibility, i.e. highest range of motion of three consecutive trials, was calculated from electrogoniometer data during active ballistic hip flexions and conventional passive slow hip-flexions in a supine position. A VAS-scale (0-100) was used to estimate experience of insecurity during active tests.

    RESULTS: No significant test-retest differences were observed. Intra-class correlation coefficients ranged 0.94-0.99 and coefficients of variation 1.52-4.53%. Active flexibility was greater (23%) than passive flexibility. In the athletes, the injured leg showed smaller (8%) active, but not passive, flexibility than the uninjured leg. Average insecurity estimation was 52 (range 28-98) for the injured and 0 for the uninjured leg, respectively.

    CONCLUSION: The new test showed high reliability and construct validity; furthermore, it seems to be sensitive enough to detect differences both in active flexibility and in insecurity after acute hamstring strains at a point in time when the commonly used clinical examination fails to reveal injury signs. Thus, the test could be a complement to the common clinical examination before the final decision to return to sport is made.

  • 18.
    Askling, Carl
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Saartok, Tönö
    Thorstensson, Alf
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Type of acute hamstring strain affects flexiblility, strength and time to return to pre-injury level2006In: British Journal of Sports Medicine, ISSN 0306-3674, E-ISSN 1473-0480, Vol. 40, p. 40-44Article in journal (Refereed)
  • 19.
    Askling, Carl
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Tengvar, M
    Saartok, T
    Thorstensson, Alf
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Sports related hamstring strains--two cases with different etiologies and injury sites.2000In: Scandinavian Journal of Medicine and Science in Sports, ISSN 0905-7188, E-ISSN 1600-0838, Vol. 10, no 5, p. 304-7Article in journal (Refereed)
    Abstract [en]

    Hamstring strains are common injuries in sports. Knowledge about their etiology and localization is, however, limited. The two cases described here both had acute hamstring strains, but the etiologies were entirely different. The sprinter was injured when running at maximal speed, whereas the hamstring strain in the dancer occurred during slow stretching. Also the anatomical localizations of the injuries clearly differed. Magnetic resonance imaging (MRI) revealed pathological changes in the distal semitendinosus muscle in the sprinter and the proximal tendon of the semimembranosus muscle in the dancer. Subjectively, both athletes severely underestimated the recovery time. These case observations suggest a possible link between etiology and localization of hamstring strains.

  • 20. Barnard, R J
    et al.
    Duncan, H W
    Thorstensson, Alf T
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Heart rate responses of young and old rats to various levels of exercise.1974In: Journal of applied physiology, ISSN 0021-8987, Vol. 36, no 4, p. 472-4Article in journal (Refereed)
  • 21. Bergh, U
    et al.
    Thorstensson, Alf
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Sjödin, B
    Hulten, B
    Piehl, K
    Karlsson, J
    Maximal oxygen uptake and muscle fiber types in trained and untrained humans.1978In: Medicine and science in sports, ISSN 0025-7990, Vol. 10, no 3, p. 151-4Article in journal (Refereed)
    Abstract [en]

    Maximal oxygen uptake (Vo2 max) was determined in 138 male and 41 female human subjects and muscle fiber composition (gastrocnemius and vastus lateralis) in 53 of the males. Highest values for Vo2 max were 7.38 1 x min-1 and 4.341 x min-1 in males and females, respectively. In relation to body weight the highest values were 94 and 77 ml x (kg x min)-1. Athletes participating in endurance events had very high Vo2 max and predominantly slow twitch (ST) fiber populations whereas weight lifters attained rather low values for Vo2 max and had a higher percentage of fast twitch (FT) fibers. Among subjects with the same fiber composition, Vo2 max was higher in the athletes than in the moderately trained. All groups taken together demonstrated a positive relationship between Vo2 max and the relative number of ST fibers (r = 0.67). For endurance and strength athletes r = 0.72 and for the moderately trained r = 0.34, both correlation coefficients being significant.

  • 22.
    Bjerkefors, Anna
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Carpenter, M G
    Thorstensson, Alf
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Dynamic trunk stability is improved in paraplegics following kayak ergometer training.2007In: Scandinavian Journal of Medicine and Science in Sports, ISSN 0905-7188, E-ISSN 1600-0838, Vol. 17, no 6, p. 672-9Article in journal (Refereed)
    Abstract [en]

    The purpose of the study was to assess whether postural stability in persons with spinal cord injury (SCI) could be affected by training. Ten post-rehabilitated persons with thoracic SCI performed 30 sessions of kayak ergometer training during a 10-week period. The ergometer was modified with a balance module adjustable in the medio-lateral direction. Before and after the training period, horizontal support-surface translations were presented randomly, either in the forward or backward direction, or to the side, while subjects sat in their own wheelchairs. The platform perturbation consisted of an unpredictable initial acceleration, followed by a constant-velocity phase and a predictable deceleration. Markers were applied on the trunk and movement data were recorded in 3D. Four kinematic responses of trunk angular and linear displacement were investigated. In general, postural stability was improved after training with smaller rotational and linear displacements of the trunk observed during both predictable and unpredictable translations in all directions. Thus, the training was able to improve the ability of persons with long-standing SCI to maintain an upright sitting posture in response to externally generated balance perturbations, which should imply an increased capacity to master similar challenges to balance in everyday life.

  • 23.
    Bjerkefors, Anna
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Carpenter, Mark G
    Cresswell, Andrew G
    Thorstensson, Alf
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Trunk muscle activation in a person with clinically complete thoracic spinal cord injury.2009In: Journal of rehabilitation medicine : official journal of the UEMS European Board of Physical and Rehabilitation Medicine, ISSN 1651-2081, Vol. 41, no 5, p. 390-2Article in journal (Refereed)
    Abstract [en]

    OBJECTIVE: The aim of this study was to assess if, and how, upper body muscles are activated in a person with high thoracic spinal cord injury, clinically classified as complete, during maximal voluntary contractions and in response to balance perturbations. METHODS: Data from one person with spinal cord injury (T3 level) and one able-bodied person were recorded with electromyography from 4 abdominal muscles using indwelling fine-wire electrodes and from erector spinae and 3 upper trunk muscles with surface electrodes. Balance perturbations were carried out as forward or backward support surface translations. RESULTS: The person with spinal cord injury was able to activate all trunk muscles, even those below the injury level, both in voluntary efforts and in reaction to balance perturbations. Trunk movements were qualitatively similar in both participants, but the pattern and timing of muscle responses differed: upper trunk muscle involvement and occurrence of co-activation of ventral and dorsal muscles were more frequent in the person with spinal cord injury. CONCLUSION: These findings prompt further investigation into trunk muscle function in paraplegics, and highlight the importance of including motor tests for trunk muscles in persons with thoracic spinal cord injury, in relation to injury classification, prognosis and rehabilitation.

  • 24.
    Bjerkefors, Anna
    et al.
    Swedish School of Sport and Health Sciences, GIH.
    Carpenter, MG
    Cresswell, AG
    Thorstensson, Alf
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences.
    Trunk muscle responses to balance perturbations in paraplegicsManuscript (Other academic)
  • 25.
    Bjerkefors, Anna
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Jansson, A
    Thorstensson, Alf
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Shoulder muscle strength in paraplegics before and after kayak ergometer training2006In: European Journal of Applied Physiology, ISSN 1439-6319, E-ISSN 1439-6327, Vol. 97, no 5, p. 613-8Article in journal (Refereed)
    Abstract [en]

    The purpose was to investigate if shoulder muscle strength in post-rehabilitated persons with spinal cord injury (SCI) was affected by kayak ergometer training and to compare shoulder strength in persons with SCI and able-bodied persons. Ten persons with SCI (7 males and 3 females, injury levels T3-T12) performed 60 min kayak ergometer training three times a week for 10 weeks with progressively increased intensity. Maximal voluntary concentric contractions were performed during six shoulder movements: flexion and extension (range of motion 65 degrees ), abduction and adduction (65 degrees ), and external and internal rotation (60 degrees ), with an angular velocity of 30 degrees s(-1). Position specific strength was assessed at three shoulder angles (at the beginning, middle and end of the range of motion) in the respective movements. Test-retests were performed for all measurements before the training and the mean intraclass correlation coefficient was 0.941 (95% CI 0.928-0.954). There was a main effect of kayak ergometer training with increased shoulder muscle strength after training in persons with SCI. The improvements were independent of shoulder movement, and occurred in the beginning and middle positions. A tendency towards lower shoulder muscle strength was observed in the SCI group compared to a matched reference group of able-bodied persons. Thus, it appears that post-rehabilitated persons with SCI have not managed to fully regain/maintain their shoulder muscle strength on a similar level as that of able-bodied persons, and are able to improve their shoulder muscle strength after a period of kayak ergometer training.

  • 26.
    Bjerkefors, Anna
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Nordlund Ekblom, Maria M
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Josefsson, Karin
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Thorstensson, Alf
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Deep and superficial abdominal muscle activation during trunk stabilization exercises with and without instruction to hollow.2010In: Manual Therapy, ISSN 1356-689X, E-ISSN 1532-2769, Vol. 15, no 5, p. 502-7Article in journal (Refereed)
    Abstract [en]

    The deepest muscle of the human ventro-lateral abdominal wall, the Transversus Abdominis (TrA), has been ascribed a specific role in spine stabilization, which has motivated special core stability exercises and hollowing instruction to specifically involve this muscle. The purpose here was to evaluate the levels of activation of the TrA and the superficial Rectus Abdominis (RA) muscles during five common stabilization exercises performed in supine, bridging and four-point kneeling positions, with and without instruction to hollow, i.e. to continuously pull the lower part of the abdomen towards the spine. Nine habitually active women participated and muscle activity was recorded bilaterally from TrA and RA with intramuscular fine-wire electrodes introduced under the guidance of ultrasound. Results showed that subjects were able to selectively increase the activation of the TrA, isolated from the RA, with the specific instruction to hollow and that side differences in the amplitude of TrA activity, related to the asymmetry of the exercises, remained even after the instruction to hollow. The exercises investigated caused levels of TrA activation from 4 to 43% of that during maximal effort and can thus be used clinically to grade the load on the TrA when designing programs aiming at training that muscle.

  • 27.
    Bjerkefors, Anna
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Thorstensson, Alf
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Effects of kayak ergometer training on motor performance in paraplegics.2006In: International Journal of Sports Medicine, ISSN 0172-4622, E-ISSN 1439-3964, Vol. 27, no 10, p. 824-9Article in journal (Refereed)
    Abstract [en]

    The purpose of this study was to assess the effects of kayak ergometer training on functional tests performed in wheelchair by persons with spinal cord injury. Ten post-rehabilitated persons with thoracic spinal cord injury volunteered for the study and performed 30 sessions of kayak ergometer training during a 10-week period. The ergometer was modified with an additional balance demand in the medio-lateral direction. Before and after the training period the subjects performed functional tests in the wheelchair: Sit-and-reach tests (distance), mounting a platform, transfer to a bench (height), propelling the wheelchair: 5 m on the rear wheels; in a figure-8; 15 m on a level surface and 50 m on a 3 degrees inclined surface (time). Test-retests were performed for all tests before the training began. A written questionnaire was distributed to evaluate the subjective experiences of the training. The test-retest resulted in coefficient of variation of 1.3 - 4.6 %. There were significant improvements in sit-and-reach (14 %), mounting a platform (7 %), transfer to a bench (10 %), propelling on level (3 %), and inclined surface (6 %). Furthermore, the training, did not cause any shoulder pain or other problems. This, and the positive subjective experience expressed by the subjects after the training indicate that this type of training is a suitable activity for persons with thoracic spinal cord injury.

  • 28. Bonnard, M
    et al.
    Sirin, A V
    Oddsson, L
    Thorstensson, Alf
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Different strategies to compensate for the effects of fatigue revealed by neuromuscular adaptation processes in humans.1994In: Neuroscience Letters, ISSN 0304-3940, E-ISSN 1872-7972, Vol. 166, no 1, p. 101-5Article in journal (Refereed)
    Abstract [en]

    An initially submaximal hopping task was maintained with the same global power output until it became the maximal performance; since there was no decrease in performance, any change in behavior occurring with fatigue characterizes the strategies allowing to compensate for the effects of fatigue. In a prolonged hopping task, fatigue is likely to be most prominent in the ankle extensor muscles since they are the main contributors to vertical propulsion in the hop. With fatigue, all subjects landed with more flexed knees and with an increased activity in the biarticular rectus femoris muscle indicating some compensation between the knee and ankle joint. Furthermore, two different strategies appeared to further compensate for the important fatigue of the ankle extensor muscles: one was organized across joints and consisted in a heavier reliance of the knee extensor vastus lateralis, and the other was organized within the fatigued joint and consisted in an earlier preactivation of the gastrocnemius. As a consequence, two different adaptations of the ground reaction force profiles appeared at the end of the session; each being related to one of these two strategies.

  • 29. Carlson, H
    et al.
    Nilsson, Johnny
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Thorstensson, Alf
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Zomlefer, M R
    Motor responses in the human trunk due to load perturbations.1981In: Acta Physiologica Scandinavica, ISSN 0001-6772, E-ISSN 1365-201X, Vol. 111, no 2, p. 221-3Article in journal (Refereed)
  • 30. Carlson, H
    et al.
    Thorstensson, Alf
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Nilsson, Johnny
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Lumbar back muscle activity during locomotion: effects of voluntary modifications of normal trunk movements.1988In: Acta Physiologica Scandinavica, ISSN 0001-6772, E-ISSN 1365-201X, Vol. 133, no 3, p. 343-53Article in journal (Refereed)
    Abstract [en]

    The mechanisms of adaptation of the trunk to changed mechanical conditions were studied during locomotion in man. The myoelectrical (EMG) activity in lumbar back muscles and the movements of the trunk were recorded in nine healthy subjects during walking and running on a motor-driven treadmill. Two different types of voluntary modifications of the movement pattern were used: (1) The trunk was kept in an extreme forward or backward tilted position. In both these situations the basic EMG pattern with two periods of activity per stride cycle was maintained during walking, whereas a major shift relative to the stride cycle (25% of the stride cycle duration) occurred in running with the trunk tilted backwards. The synchrony of the back muscle activation at both sides increased when locomotion was performed with the trunk tilted forwards. The relative duration of the EMG bursts was similar to normal locomotion and corresponded to 15-26% of the stride cycle duration in walking and 23-37% in running. (2) In the other type of modification the subjects were instructed to exaggerate the angular trunk movements either in the sagittal or in the frontal plane. The basic EMG pattern and phase relationships remained in most cases unchanged. One exception was running with exaggerated lateral movements, in which only one period of back muscle activity per stride cycle was observed. The relative duration of the bursts was longer in trials with exaggerated trunk movements as compared to normal locomotion. In walking and running with the trunk tilted forwards or backwards the lumbar back muscles were not always involved as prime movers of the trunk. This was in contrast to the more dynamic situations, in which the back muscle activity appeared to be directly involved in braking and reversing the exaggerated trunk movements.

  • 31. Carpenter, Mark G
    et al.
    Thorstensson, Alf
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Cresswell, Andrew G
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences.
    Deceleration affects anticipatory and reactive components of triggered postural responses.2005In: Experimental Brain Research, ISSN 0014-4819, E-ISSN 1432-1106, Vol. 167, no 3, p. 433-45Article in journal (Refereed)
    Abstract [en]

    Understanding the physiological and psychological factors that contribute to healthy and pathological balance control in man has been made difficult by the confounding effects of the perturbations used to test balance reactions. The present study examined how postural responses were influenced by the acceleration-deceleration interval of an unexpected horizontal translation. Twelve adult males maintained balance during unexpected forward and backward surface translations with two different acceleration-deceleration intervals and presentation orders (serial or random). "SHORT" perturbations consisted of an initial acceleration (peak acceleration 1.3 m s(-2); duration 300 ms) followed 100 ms later by a deceleration. "LONG" perturbations had the same acceleration as SHORT perturbations, followed by a 2-s interval of constant velocity before deceleration. Surface and intra-muscular electromyography (EMG) from the leg, trunk, and shoulder muscles were recorded along with motion and force plate data. LONG perturbations induced larger trunk displacements compared to SHORT perturbations when presented randomly and larger EMG responses in proximal and distal muscles during later (500-800 ms) response intervals. During SHORT perturbations, activity in some antagonist muscles was found to be associated with deceleration and not the initial acceleration of the support surface. When predictable, SHORT perturbations facilitated the use of anticipatory mechanisms to attenuate early (100-400 ms) EMG response amplitudes, ankle torque change and trunk displacement. In contrast, LONG perturbations, without an early deceleration effect, did not facilitate anticipatory changes when presented in a predictable order. Therefore, perturbations with a short acceleration-deceleration interval can influence triggered postural responses through reactive effects and, when predictable with repeated exposure, through anticipatory mechanisms.

  • 32. Carpenter, Mark G
    et al.
    Tokuno, Craig D
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Thorstensson, Alf
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Cresswell, Andrew G
    Differential control of abdominal muscles during multi-directional support-surface translations in man.2008In: Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale, ISSN 1432-1106, Vol. 188, no 3, p. 445-55Article in journal (Refereed)
    Abstract [en]

    The current study aimed to understand how deep and superficial abdominal muscles are coordinated with respect to activation onset times and amplitudes in response to unpredictable support-surface translations delivered in multiple directions. Electromyographic (EMG) data were recorded intra-muscularly using fine-wire electrodes inserted into the right rectus abdominis (RA), obliquus externus (OE), obliquus internus (OI) and transversus abdominis (TrA) muscles. Twelve young healthy male subjects were instructed to maintain their standing balance during 40 support surface translations (peak acceleration 1.3 m s(-2); total displacement 0.6 m) that were counter-balanced between four different directions (forward, backward, leftward, rightward). Differences between abdominal muscles in EMG onset times were found for specific translation directions. The more superficial RA (backward translations) and OE (forward and leftward translations) muscles had significantly earlier EMG onsets compared to TrA. EMG onset latencies were dependent on translation direction in RA, OE and OI, but independent of direction in TrA. EMG amplitudes in RA and OE were dependent on translation direction within the first 100 ms of activity, whereas responses from the two deeper muscles (TrA and OI) were independent of translation direction during this interval. The current results provide new insights into how abdominal muscles contribute to postural reactions during human stance. Response patterns of deep and superficial abdominal muscles during support surface translations are unlike those previously described during upper-body perturbations or voluntary arm movements, indicating that the neural mechanisms controlling individual abdominal muscles are task-specific to different postural demands.

  • 33. Cresswell, A G
    et al.
    Blake, P L
    Thorstensson, Alf
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    The effect of an abdominal muscle training program on intra-abdominal pressure.1994In: Scandinavian Journal of Rehabilitation Medicine, ISSN 0036-5505, E-ISSN 1940-2228, Vol. 26, no 2, p. 79-86Article in journal (Refereed)
    Abstract [en]

    The effect of 10 weeks' specific abdominal strength training (resisted trunk rotations) on intra-abdominal pressure was investigated in 10 healthy males. Isometric rotational force, trunk flexor and extensor torque and intra-abdominal pressure were measured as well as intra-abdominal pressure responses to Valsalva manoeuvres, maximal pulsed pressures, drop jumps and trunk perturbations. The rotational strength increased 29.7% after training without significant change in intra-abdominal pressure. The isometric flexor strength did not change, while the extensor strength increased 11.0%. Valsalva and pulsed pressures increased 11.6 and 9.2%, respectively. The rate of intra-abdominal pressure development during pulsed pressures, drop jumps and trunk perturbations increased after training. The level of intra-abdominal pressure during the latter two tasks remained unchanged. It is concluded that an increase in strength of the trunk rotators with training improves the ability to generate higher levels of voluntarily induced intra-abdominal pressure and increases the rate of intra-abdominal pressure development during functional situations.

  • 34. Cresswell, A G
    et al.
    Grundström, H
    Thorstensson, Alf
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Observations on intra-abdominal pressure and patterns of abdominal intra-muscular activity in man.1992In: Acta Physiologica Scandinavica, ISSN 0001-6772, E-ISSN 1365-201X, Vol. 144, no 4, p. 409-18Article in journal (Refereed)
    Abstract [en]

    The aim was to investigate possible relationships between activities of the individual muscles of the ventrolateral abdominal wall and the development of pressure within the abdominal cavity. Intra-muscular activity was recorded bilaterally from transversus abdominis, obliquus internus, obliquus externus and rectus abdominis with fine-wire electrodes guided into place using real-time ultrasound. Intra-abdominal pressure was measured intragastrically using a micro tip pressure transducer. Six males were studied during loading and movement tasks with varied levels of intra-abdominal pressure. During both maximal voluntary isometric trunk flexion and extension, transversus abdominis activity and intra-abdominal pressure remained constant, while all other abdominal muscles showed a marked reduction during extension. When maximal isometric trunk flexor or extensor torques were imposed upon a maximal Valsalva manoeuvre, transversus abdominis activity and intra-abdominal pressure remained comparable within and across conditions, whereas obliquus internus, obliquus externus and rectus abdominis activities either markedly increased (flexion) or decreased (extension). Trunk twisting movements showed reciprocal patterns of activity between the left and right sides of transversus abdominis, indicating an ability for torque development. During trunk flexion--extension, transversus abdominis showed less distinguished changes of activity possibly relating to a general stabilizing function. In varied pulsed Valsalva manoeuvres, changes in peak intra-abdominal pressure were correlated with mean amplitude electromyograms of all abdominal muscles, excluding rectus abdominis. It is concluded that the co-ordinative patterns shown between the muscles of the ventrolateral abdominal wall are task specific based upon demands of movement, torque and stabilization. It appears that transversus abdominis is the abdominal muscle whose activity is most consistently related to changes in intra-abdominal pressure.

  • 35. Cresswell, A G
    et al.
    Oddsson, L
    Thorstensson, Alf
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    The influence of sudden perturbations on trunk muscle activity and intra-abdominal pressure while standing.1994In: Experimental Brain Research, ISSN 0014-4819, E-ISSN 1432-1106, Vol. 98, no 2, p. 336-41Article in journal (Refereed)
    Abstract [en]

    Unexpected ventral and dorsal perturbations and expected, self-induced ventral perturbations were delivered to the trunk by suddenly loading a vest strapped to the torso. Six male subjects were measured for intra-abdominal pressure (IAP) and intra-muscular electromyography of the transversus abdominis (TrA), obliquus internus abdominis (OI), obliquus externus abdominis (OE) and rectus abdominis (RA) muscles. Erector spinae (ES) activity was recorded using surface electromyography. Displacements of the trunk and head were registered using a video-based system. Unexpected ventral loading produced activity in TrA, OI, OE and RA, and an IAP increase well in advance of activity from ES. Expected ventral loading produced pre-activation of all muscles and an increased IAP prior to the perturbation. The TrA was always the first muscle active in both the unexpected and self-loading conditions. Of the two ventral loading conditions, forward displacement of the trunk was significantly reduced during the self-loading. Unexpected dorsal loading produced coincident activation of TrA, OI, OE, RA and ES. These results indicate a response of the trunk muscles to sudden expected and unexpected ventral loadings other than the anticipated immediate extensor torque production through ES activation. It is suggested that the increase in IAP is a mechanism designed to improve the stability of the trunk through a stiffening of the whole segment.

  • 36. Cresswell, A G
    et al.
    Thorstensson, Alf
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Changes in intra-abdominal pressure, trunk muscle activation and force during isokinetic lifting and lowering.1994In: European Journal of Applied Physiology and Occupational Physiology, ISSN 0301-5548, E-ISSN 1432-1025, Vol. 68, no 4, p. 315-21Article in journal (Refereed)
    Abstract [en]

    Intra-abdominal pressure (IAP), force and electromyographic (EMG) activity from the abdominal (intra-muscular) and trunk extensor (surface) muscles were measured in seven male subjects during maximal and sub-maximal sagittal lifting and lowering with straight arms and legs. An isokinetic dynamometer was used to provide five constant velocities (0.12-0.96 m.s-1) of lifting (pulling against the resistance of the motor) and lowering (resisting the downward pull of the motor). For the maximal efforts, position-specific lowering force was greater than lifting force at each respective velocity. In contrast, corresponding IAPs during lowering were less than those during lifting. Highest mean force occurred during slow lowering (1547 N at 0.24 m.s-1) while highest IAP occurred during the fastest lifts (17.8 kPa at 0.48-0.96 m.s-1). Among the abdominal muscles, the highest level of activity and the best correlation to variations in IAP (r = 0.970 over velocities) was demonstrated by the transversus abdominis muscle. At each velocity the EMG activity of the primary trunk and hip extensors was less during lowering (eccentric muscle action) than lifting (concentric muscle action) despite higher levels of force (r between -0.896 and -0.851). Sub-maximal efforts resulted in IAP increasing linearly with increasing lifting or lowering force (r = 0.918 and 0.882, respectively). However, at any given force IAP was less during lowering than lifting. This difference was negated if force and IAP were expressed relative to their respective lifting and lowering maxima.(ABSTRACT TRUNCATED AT 250 WORDS)

  • 37. Cresswell, A G
    et al.
    Thorstensson, Alf
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    The role of the abdominal musculature in the elevation of the intra-abdominal pressure during specified tasks.1989In: Ergonomics, ISSN 0014-0139, E-ISSN 1366-5847, Vol. 32, no 10, p. 1237-46Article in journal (Refereed)
    Abstract [en]

    A series of standardized tasks, isometric trunk flexion and extension and maximal Valsalva manoeuvres, were used to evaluate the role of the abdominal musculature in developing an increased intra-abdominal pressure (IAP). Seven male subjects were measured for IAP, myoelectric activity of rectus abdominis (RA), obliquus externus and internus (OE and OI respectively), erector spinae (ES) and isometric trunk torque. IAPs in all experimental conditions were markedly greater than those that occurred while relaxed. In isometric trunk flexion, IAPs were increased with accompanying high levels of activity from the abdominal muscles. In contrast, little activity from the abdominal muscles occurred during isometric trunk extension, although levels of IAP were similar to those found in the isometric flexion condition. With maximal voluntary pressurization (Valsalva manoeuvre) slightly higher levels of IAP than those found in torque conditions were recorded, this pressure being produced with abdominal activities (OE and OI) less than one fourth their recorded maximum. When isometric torque tasks were added to the Valsalva manoeuvre, patterns of muscle activity (RA, OE, OI and ES) were significantly altered. For Valsalva with isometric trunk extension, activity from OE and OI was reduced while IAPs remained fairly constant. These findings indicate that in tasks where an IAP extension moment is warranted, abdominal pressure can be increased without the development of a large counter-moment produced by the dual action of the trunk flexors. Activation of other muscles such as the diaphragm and transversus abdominis is suggested as helping provide control over the level of IAP during controlled trunk tasks.

  • 38. Cresswell, Andrew G
    et al.
    Löscher, W N
    Thorstensson, Alf
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Influence of gastrocnemius muscle length on triceps surae torque development and electromyographic activity in man.1995In: Experimental Brain Research, ISSN 0014-4819, E-ISSN 1432-1106, Vol. 105, no 2, p. 283-90Article in journal (Refereed)
    Abstract [en]

    The present study was designed to determine the relative contribution of the gastrocnemius muscle to isometric plantar flexor torque production at varying knee angles, while investigating the activation of the gastrocnemius muscle at standardised non-optimal lengths. Voluntary plantar flexor torque, supramaximally stimulated twitch torque and myoelectric activity (EMG) from the triceps surae were measured at different knee angles. Surface and intra-muscular EMG were recorded from the soleus muscle and the medial and lateral heads of the gastrocnemius muscle in 10 male subjects. With the ankle angle held constant, knee angle was changed in steps of 30 degrees ranging from 180 degrees (extended) to 60 degrees (extreme flexion), while voluntary torque from a 5-s contraction was determined at 10 different levels of voluntary effort, ranging from 10% of maximal effort to maximal effort. To assess effort, supramaximal twitches were superimposed on all voluntary contractions, and additionally during rest. Maximal plantar flexor torque and resting twitch torque decreased significantly in a sigmoidal fashion with increasing knee flexion to 60% of the maximum torque at 180 degrees knee angle. For similar levels of voluntary effort, the EMG root mean square (RMS) of gastrocnemius was less with increased knee flexion, whereas soleus RMS remained unchanged. From these data, it is concluded that the contribution of gastrocnemius to plantar flexor torque is at least 40% of the total torque in the straight leg position. The decrease of gastrocnemius EMG RMS with decreasing muscle length may be brought about by a decrease in the number of fibres within the EMG electrode recording volume and/or impaired neuromuscular transmission.

  • 39.
    Crommert, M Eriksson
    et al.
    Örebro Universitet.
    Nordlund Ekblom, Maria M
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Thorstensson, Alf
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Activation of transversus abdominis varies with postural demand in standing.2011In: Gait & Posture, ISSN 0966-6362, E-ISSN 1879-2219, Vol. 33, no 3, p. 473-7Article in journal (Refereed)
    Abstract [en]

    Transversus abdominis (TrA) is a multifunctional muscle, being involved in pressure regulation within the abdominal cavity and thereby in direction independent stabilization of the spine and resistance to imposed trunk flexion moments. Indirect evidence suggests a role of TrA also in postural control of the erect human trunk. The main purpose here was to investigate if the magnitude of TrA activation is related to postural demand. Eleven healthy males performed seven different symmetrical static bilateral arm positions holding 3 kg in each hand. The arm positions were selected to systematically vary the height of the centre of mass (COM) keeping imposed moments constant and vice versa. EMG was recorded bilaterally with fine-wire intramuscular electrodes from TrA and obliquus internus (OI) and with surface electrodes from rectus abdominis (RA) and erector spinae (ES). Intra-abdominal pressure (IAP) was measured via a pressure transducer in the gastric ventricle. TrA was the only muscle that displayed activation co-varying with the vertical position of the COM. Further, TrA activation increased, together with IAP and ES activation, with imposed flexion moment, i.e. with arms extended horizontally forward. In contrast to OI, RA and ES, TrA activation was independent of the direction of the imposed moment (arms held inclined forward or backward). In conclusion, TrA activation level is uniquely associated with increased postural demand caused by elevated COM. Also, TrA appears to assist in counteracting trunk flexion via increased IAP, and contribute to general spine stabilization when the trunk is exposed to moderate flexion and extension moments.

  • 40.
    Daggfeldt, Karl
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Huang, Q M
    Thorstensson, Alf
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    The visible human anatomy of the lumbar erector spinae.2000In: Spine, ISSN 0362-2436, E-ISSN 1528-1159, Vol. 25, no 21, p. 2719-25Article in journal (Refereed)
    Abstract [en]

    STUDY DESIGN: Image data of the male and female cadavers from the Visible Human Project were visualized and quantified. OBJECTIVE: To clarify the anatomy of the lumbar part of the human lumbar erector spinae muscles. SUMMARY OF BACKGROUND DATA: Recent studies have shown discrepancies in the description of the anatomy of the lumbar part of the lumbar erector spinae. The main differences concern whether lumbar fascicles of iliocostalis lumborum exist and whether the lumbar fascicles have direct attachments to the ilium or attach via the erector spinae aponeurosis. With the Visible Human Project from the U.S. National Library of Medicine, a new powerful basis for anatomic investigation has become available. METHODS: Software was produced to visualize sections oriented in any direction and with maximum resolution of the Visible Human male and female. Three-dimensional coordinates of anatomic structures in the image space could be marked in the cross-sectional images. The geometry and the physiologic cross-sectional areas of the erector spinae fascicles of lumbar origin were thus derived. RESULTS AND CONCLUSIONS: The study supports a classification of the lateral fascicles of the lumbar part of the lumbar erector spinae as part of iliocostalis lumborum. In both the male and the female, a large part of the erector spinae fibers of lumbar origin attached to the erector spinae aponeurosis. These results are of importance for biomechanical analysis of force transmission in the lumbar spine.

  • 41.
    Daggfeldt, Karl
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Thorstensson, Alf
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    The mechanics of back-extensor torque production about the lumbar spine.2003In: Journal of Biomechanics, ISSN 0021-9290, E-ISSN 1873-2380, Vol. 36, no 6, p. 815-25Article in journal (Refereed)
    Abstract [en]

    The purpose of this study was to develop and evaluate a biomechanical model of lumbar back extension over a wide range of positions for the lumbar spine, incorporating the latest information on muscle geometry and intra-abdominal pressure (IAP). Analysis of the Visible Human data was utilised in order to obtain anatomical information unavailable from the literature and magnetic resonance imaging was used to generate subject-specific anatomical descriptions. The model was evaluated by comparisons with measured maximal voluntary static back-extension torques. Predicted maximal specific muscle tensions agreed well with in vitro measurements from the literature. When modelling the maximal static back-extension torque production, it was possible to come fairly close to simultaneous equilibrium about all the lumbar discs simply by a uniform muscle activation of all back-extensor muscles (the caudal part showed, however, less agreement). This indicates that equilibrium in the lumbar spine is mainly regulated by passive mechanical properties, e.g. muscle length changes due to postural changes, rather than due to complex muscle coordination, as earlier proposed. The model showed that IAP (measured during torque exertions) contributes about 10% of the total maximal voluntary back-extensor torque and that it can unload the spine from compression. The spinal unloading effect from the IAP was greatest with the spine held in a flexed position. This is in opposition to the effects of changed muscle lever arm lengths, which for a given load would give the largest spinal unloading in the extended position. These findings have implications for the evaluation of optimal lifting techniques.

  • 42.
    Daggfeldt, Karl
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Thorstensson, Alf
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    The role of intra-abdominal pressure in spinal unloading.1997In: Journal of Biomechanics, ISSN 0021-9290, E-ISSN 1873-2380, Vol. 30, no 11-12, p. 1149-55Article in journal (Refereed)
    Abstract [en]

    Previous studies on how an increase in intra-abdominal pressure (IAP) effects the loading of the lumbar spine during back extension show diverging results. From a critical review of the literature we deduce a simplified, but consistent, model of the mechanisms involved in IAP-induced unloading of the lumbar spine. The model is then expanded by explicitly incorporating equilibrium equations for the pressurised abdomen and the abdominal wall. It is shown that the unloading effect of IAP can be viewed as that of a pressurised column of fixed cross-sectional area, between the rib cage and pelvis. Different abdominal forms are examined and a form with zero longitudinal curvature is found to have some important mechanical benefits for the generation of IAP-induced alleviation of compressive loading of the lumbar spine.

  • 43.
    Ekblom, Björn
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Björn Ekblom's research group.
    Huot, R
    Stein, E M
    Thorstensson, Alf T
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Effect of changes in arterial oxygen content on circulation and physical performance.1975In: Journal of applied physiology, ISSN 0021-8987, Vol. 39, no 1, p. 71-5Article in journal (Refereed)
    Abstract [en]

    To evaluate the effect of different levels of arterial oxygen content on hemodynamic parameters during exercise nine subjects performed submaximal bicycle or treadmill exercise and maximal treadmill exercise under three different experimental conditions: 1) breathing room air (control); 2) breathing 50% oxygen (hyperoxia); 3) after rebreathing a carbon monoxide gas mixture (hypoxia). Maximal oxygen consumption (Vo2 max) was significantly higher in hyperoxia (4.99 1/min) and significantly lower in hypoxia (3.80 1/min) than in the control experiment (4.43 1/min). Physical performance changes in parallel with Vo2 max. Maximal cardiac output (Qmax) was similar in hyperoxia as in control but was significantly lower in hypoxia mainly due to a decreased stroke volume. A correlation was found between Vo2 max and transported oxygen, i.e., Cao2 times Amax, thus suggesting that central circulation is an important limiting factor for human maximal aerobic power. During submaximal work HR was decreased in hyperoxia and increased in hypoxia. Corresponding Q values were unchanged except for a reduction during high submaximal exercise in hyperoxia.

  • 44.
    Ekblom, Maria M Nordlund
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Thorstensson, Alf
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Effects of prolonged vibration on H-reflexes, muscle activation, and dynamic strength.2011In: Medicine & Science in Sports & Exercise, ISSN 0195-9131, E-ISSN 1530-0315, Vol. 43, no 10, p. 1933-9Article in journal (Refereed)
    Abstract [en]

     Neural activation is generally lower during maximal voluntary lengthening compared with shortening and isometric muscle actions, but the mechanisms underlying these differences are unclear. In maximal voluntary isometric actions, reduced Ia-afferent input induced by prolonged tendon vibration has been shown to impair neural activation and strength.

    PURPOSE: This study aimed to investigate whether reducing Ia-afferent input influences neural activation in maximal voluntary dynamic muscle actions and, if so, whether it affects shortening and lengthening muscle actions differently.

    METHODS: Eight women participated in three familiarization sessions and two randomly ordered experiments. In one experiment, 30-min vibration at 100 Hz was applied to the Achilles tendon to decrease Ia-afferent input as measured by the H-reflex. In the control experiment, rest substituted the vibration. Root mean square EMG from plantar and dorsiflexor muscles and plantar flexor strength were measured during maximal voluntary plantar flexor shortening and lengthening actions (20°·s(-1)) before and after vibration and rest, respectively. Soleus H-reflexes and M-waves were elicited before each set of strength tests.

    RESULTS: The vibration caused a decrease in H-reflex amplitude by, on the average, 33%, but root mean square EMG and plantar flexor strength remained largely unaffected in both action types.

    CONCLUSIONS: The findings suggest that Ia-afferent input may not substantially contribute to maximal voluntary dynamic muscle strength of the plantar flexor muscles, as tested here, and thus, the results do not support the notion that Ia-afferent excitation would contribute differently to neural activation in maximal voluntary lengthening and shortening muscle actions.

  • 45.
    Eriksson Crommert, A E Martin
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Thorstensson, Alf
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Trunk muscle coordination in reaction to load-release in a position without vertical postural demand.2008In: Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale, ISSN 1432-1106, Vol. 185, no 3, p. 383-90Article in journal (Refereed)
    Abstract [en]

    The aim of this study was to investigate the coordination between the innermost muscle layer of the ventro-lateral abdominal wall, the transversus abdominis (TrA), and other trunk muscles, in reaction to a load-release without the postural demand of keeping the trunk upright. Eleven healthy male volunteers participated. Intramuscular fine-wire electromyography (EMG) was obtained bilaterally from the TrA, rectus abdominis (RA), obliquus externus (OE) and erector spinae (ES) muscles. The subjects lay on their right side on a horizontal swivel-table with immobilized pelvis and lower limbs and with the trunk strapped to a movable platform allowing for trunk flexion and extension. Subjects maintained trunk flexion or extension at different force levels against a static resistance, which was suddenly released. They were instructed to resume the start position as fast as possible. EMG signals were analysed with respect to amplitude and timing of muscle activation. Following released static flexion, TrA increased its activity in synergy with ES. Also in released static extension, TrA increased its activity, but now in synergy with RA and OE. The direction-independent activation of TrA indicates a role of this muscle in controlling inter-segmental movements of the lumbar spine. This function was not accompanied by an early activation of TrA as has been shown previously for trunk perturbations in standing, i.e. a situation with an additional demand of maintaining the trunk posture upright against gravity.

  • 46.
    Eriksson Crommert, A E Martin
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control. Örebro universitet.
    Thorstensson, Alf
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Trunk muscle reactions to sudden unexpected and expected perturbations in the absence of upright postural demand.2009In: Experimental Brain Research, ISSN 0014-4819, E-ISSN 1432-1106, Vol. 196, no 3, p. 385-92Article in journal (Refereed)
    Abstract [en]

    The aim was to increase the understanding of the multifunctional role of the trunk muscles in spine control, particularly transversus abdominis (TrA). In 11 healthy males, intramuscular fine-wire electromyography (EMG) was obtained bilaterally from TrA, obliquus externus (OE), rectus abdominis (RA) and erector spinae (ES). The subjects lay on their right side on a horizontal swivel-table with immobilized pelvis and lower limbs and the trunk strapped to a movable platform. Unexpected or expected release of loads attached to the table by steel cables produced a perturbation inducing either trunk flexion or extension. The timing and the amplitude of activation of TrA were independent of direction of induced trunk movement. Furthermore, timing of TrA activation was simultaneous to or later than that of the more superficial abdominal muscles. Expectation of the perturbation caused a general shortening of onset latencies. The results indicate a direction independent function of TrA in lumbar spine control. Balancing the trunk vertically appears to add specific demands, since the recruitment of TrA in relation to the other abdominal muscles differed from earlier experiments in standing.

  • 47. Eriksson Crommert, Martin
    et al.
    Ekblom, Maria
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Thorstensson, Alf
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Motor control of the trunk during a modified clean and jerk lift.2014In: Scandinavian Journal of Medicine and Science in Sports, ISSN 0905-7188, E-ISSN 1600-0838, Vol. 24, no 5, p. 758-763Article in journal (Refereed)
    Abstract [en]

    The purpose of the present study was to investigate the pattern of trunk muscle activation and intra-abdominal pressure (IAP) in a somewhat modified version of the clean and jerk lift. Nine healthy physically active male amateurs performed the exercise with a 30-kg barbell. Muscle activity was registered with electromyography from transversus abdominis (TrA) and obliquus internus (OI) using intramuscular electrodes and from rectus abdominis (RA) and erector spinae (ES) with surface electrodes. IAP was recorded with a nasogastric catheter. Measurements were made in various static positions throughout the lift and in the transitional phases separating them, both during lifting and lowering. The results demonstrated that the innermost abdominal muscle, TrA, showed increased activation levels in the two highest positions, whereas ES was most active, together with the highest IAP, in the lowest position. OI and RA showed generally little activation and no obvious trend throughout the lift. The results strengthen the view of a contributing role of TrA to the upright control of the trunk and indicate that the clean and jerk lift might constitute a whole-body exercise, still targeting the TrA muscle, in late-stage rehabilitation, especially for athletes during return to sports.

  • 48.
    Eriksson-Crommert, Martin
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Ekblom, Maria
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Thorstensson, Alf
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Effects of arm movement amplitude on the initial trunk muscle activation pattern during raptid bilateral shoulder flexions during standing2012Conference paper (Refereed)
  • 49. Frohm, A
    et al.
    Halvorsen, Kjartan
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Thorstensson, Alf
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Patellar tendon load in different types of eccentric squats.2007In: Clinical Biomechanics, ISSN 0268-0033, E-ISSN 1879-1271, Vol. 22, no 6, p. 704-11Article in journal (Refereed)
    Abstract [en]

    BACKGROUND: Differences in mechanical loading of the patellar tendon have been suggested as a reason for varying effects in rehabilitation of patellar tendinopathy using different eccentric squat exercises and devices. The aim was to characterize the magnitude and pattern of mechanical load at the knee and on the patellar tendon during four types of eccentric squat. METHODS: Subjects performed squats with a submaximal free weight and with maximal effort in a device for eccentric overloading (Bromsman), on a decline board and horizontal surface. Kinematics was recorded with a motion-capture system, reaction forces with force plates, and electromyography from three leg muscles with surface electrodes. Inverse dynamics was used to calculate knee joint kinetics. FINDINGS: Eccentric work, mean and peak patellar tendon force, and angle at peak force were greater (25-30%) for squats on decline board compared to horizontal surface with free weight, but not in Bromsman. Higher knee load forces (60-80%), but not work, were observed with Bromsman than free weight. Angular excursions at the knee and ankle were larger with decline board, particularly with free weight, and smaller in Bromsman than with free weight. Mean electromyography was greater on a decline board for gastrocnemius (13%) and vastus medialis (6%) with free weight, but in Bromsman only for gastrocnemius (7%). INTERPRETATION: The results demonstrated clear differences in the biomechanical loading on the knee during different squat exercises. Quantification of such differences provides information that could be used to explain differences in rehabilitation effects as well as in designing more optimal rehabilitation exercises for patellar tendinopathy.

  • 50. Frohm, Anna
    et al.
    Halvorsen, Kjartan
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Thorstensson, Alf
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    A new device for controlled eccentric overloading in training and rehabilitation.2005In: European Journal of Applied Physiology, ISSN 1439-6319, E-ISSN 1439-6327, Vol. 94, no 1-2, p. 168-74Article in journal (Refereed)
    Abstract [en]

    The aim of this work was to evaluate a device that allows for eccentric overload to be applied under controlled and safe conditions and it is applicable in exercises commonly used in training and rehabilitation. The machine contains a barbell, which is lowered and raised by a motor, following a predetermined velocity profile. It is capable of handling heavy loads (>500 kg) and is instrumented with a sensor to measure the velocity of the barbell and two scales to measure the vertical component of the ground reaction force. The velocity recordings of the built-in displacement sensor were found to correspond well with those obtained using a motion-capture system. Applying known weights on each scale demonstrated linearity with respect to magnitude and independence regarding location of application. The velocity of the barbell was found to be dependent on the load on the barbell and on the resisting force produced by the individual training in the machine. The combined man-machine reliability was tested using a group of habitually active males (n = 13, 28-55 years) performing squats. Peak voluntary resisting force and position at peak resistance were recorded on two occasions, showing no significant differences and a coefficient of variation of 9% and 22%, respectively. Preliminary observations from training in the machine have been positive both for increasing performance in top athletes and for causing pain relief in patients with diffuse knee problems. The possibility of feedback of the force under each foot makes individual dosage of training load possible, which is valuable, e.g. in rehabilitation of a unilateral injury.

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