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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.
    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.

  • 2. Balsom, Paul D
    et al.
    Gaitanos, G C
    Söderlund, Karin
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences.
    Ekblom, Björn
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Björn Ekblom's research group.
    High-intensity exercise and muscle glycogen availability in humans.1999In: Acta Physiologica Scandinavica, ISSN 0001-6772, E-ISSN 1365-201X, Vol. 165, no 4, p. 337-45Article in journal (Refereed)
    Abstract [en]

    This study investigated the effects of muscle glycogen availability on performance and selected physiological and metabolic responses during high-intensity intermittent exercise. Seven male subjects completed a regimen of exercise and dietary intake (48 h) to either lower and keep low (LOW-CHO) or lower and then increase (HIGH-CHO) muscle glycogen stores, on two separate occasions at least a week apart. On each occasion the subjects completed a short-term (<10 min) and prolonged (>30 min) intermittent exercise (IEX) protocol, 24 h apart, which consisted of 6-s bouts of high-intensity exercise performed at 30-s intervals on a cycle ergometer. Glycogen concentration (mean +/- SEM) in m. vastus lateralis before both IEx(short) and IEx(long) was significantly lower following LOW-CHO [180 (14), 181 (17) mmol kg (dw)(-1)] compared with HIGH-CHO [397 (35), 540 (25) mmol kg (dw)(-1)]. In both IEx(short) and IEx(long), significantly less work was performed following LOW-CHO compared with HIGH-CHO. In IEx(long), the number of exercise bouts that could be completed at a pre-determined target exercise intensity increased by 265% from 111 (14) following LOW-CHO to 294 (29) following HIGH-CHO (P < 0.05). At the point of fatigue in IEx(long), glycogen concentration was significantly lower with the LOW-CHO compared with HIGH-CHO [58 (25) vs. 181 (46) mmol kg (dw)(-1), respectively]. The plasma concentrations of adrenaline and nor-adrenaline (in IEx(short) and IEx(long)), and FFAand glycerol (in IEx(long)), increased several-fold above resting values with both experimental conditions. Oxygen uptake during the exercise periods in IEx(long), approached 70% of Vo2max. These results suggest that muscle glycogen availability can affect performance during both short-term and more prolonged high-intensity intermittent exercise and that with repeated exercise periods as short as 6 s, there can be a relatively high aerobic contribution.

  • 3.
    Blomstrand, Eva
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Eva Blomstrand's research group.
    Celsing, F
    Newsholme, E A
    Changes in plasma concentrations of aromatic and branched-chain amino acids during sustained exercise in man and their possible role in fatigue.1988In: Acta Physiologica Scandinavica, ISSN 0001-6772, E-ISSN 1365-201X, Vol. 133, no 1, p. 115-21Article in journal (Refereed)
    Abstract [en]

    The plasma concentrations of branched-chain and aromatic amino acids have been measured in two different types of sustained dynamic exercise. Twenty-two subjects participated in the 1986 Stockholm Marathon and eight subjects took part in an army training programme of approximately 1.5-h duration. Both types of exercise caused a significant decrease in the plasma concentration of branched-chain amino acids, while there was no change in the concentration of total (free plus bound to albumin) tryptophan. The plasma concentration of free tryptophan, which was measured in the marathon runners, was found to increase 2.4-fold during the race. This increase is probably caused by a pronounced elevation in the concentration of plasma free fatty acids during exercise, since these are known to displace tryptophan from albumin. The observed increase in plasma free tryptophan concentration, together with the decrease in plasma concentration of branched-chain amino acids, gives rise to a marked increase in the plasma concentration ratio of free tryptophan/branched-chain amino acids. This should lead to an increase in the rate of transport of tryptophan across the blood-brain barrier and hence to an increase in the rate of synthesis of 5-hydroxytryptamine (5-HT) in the brain. An elevated concentration of 5-HT in specific areas of the brain may be responsible, at least in part, for the development of physical, and/or mental fatigue during prolonged exercise.

  • 4.
    Blomstrand, Eva
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Eva Blomstrand's research group.
    Essén-Gustavsson, B
    Influence of reduced muscle temperature on metabolism in type I and type II human muscle fibres during intensive exercise.1987In: Acta Physiologica Scandinavica, ISSN 0001-6772, E-ISSN 1365-201X, Vol. 131, no 4, p. 569-74Article in journal (Refereed)
    Abstract [en]

    Six male subjects performed intensive cycle exercise to exhaustion after cooling their legs in water at 10-12 degrees C (muscle temperature (Tm) 28 +/- 2.6 degrees C, mean +/- SD). Exercise at exactly the same rate and duration (370 +/- 34 W, 1.5 +/- 0.2 min) was then repeated by each subject 2-5 weeks later at normal Tm (35 +/- 1.0 degrees C). Muscle biopsies were taken from the vastus lateralis muscle at rest and after exercise. The muscle tissue was freeze-dried and fragments of single fibres were dissected out. The fibres were classified and pooled into groups of type I and type II. Analyses of glycogen, glucose 6-phosphate, lactate and phosphagens were performed on pools of type-identified fibres. After exercise at reduced Tm, all subjects had higher concentrations of glucose 6-phosphate and lactate in both type I and type II fibres, and in most subjects the concentrations of ATP and phosphocreatine were lower as compared with the findings after exercise at normal Tm. During exercise the glycogen content of both fibre types decreased to a greater extent at reduced than at normal Tm in most subjects. The results suggest that during intensive dynamic exercise at reduced Tm there is a higher degree of glycolysis from glycogen in the muscle than in the normal situation. In some subjects the cause of fatigue may be related to a more rapid accumulation of lactate in the cold muscle, while in others fatigue may be related to alternative factors, e.g. low levels of ATP and phosphocreatine.

  • 5.
    Blomstrand, Eva
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Eva Blomstrand's research group.
    Hassmén, Peter
    Ek, S
    Ekblom, Björn
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Björn Ekblom's research group.
    Newsholme, E A
    Influence of ingesting a solution of branched-chain amino acids on perceived exertion during exercise.1997In: Acta Physiologica Scandinavica, ISSN 0001-6772, E-ISSN 1365-201X, Vol. 159, no 1, p. 41-9Article in journal (Refereed)
    Abstract [en]

    On two occasions, seven male endurance-trained cyclists performed exhaustive exercise on a cycle ergometer in the morning after they had performed a bout of exercise the preceding evening in an attempt to lower the muscle glycogen stores. The subjects exercised at a work rate corresponding to approximately 70% of their maximal oxygen uptake for 60 min, followed by another 20 min of maximal exercise. During exercise the subjects were given either a solution of branched-chain amino acids (BCAAs) or flavoured water (placebo). Every 10 min during exercise the subjects rated their perceived exertion and mental fatigue on two different Borg scales. During the 60 min exercise at a given work rate the subjects ratings of perceived exertion when they were given BCAAs were 7% lower, and their ratings of mental fatigue were 15% lower than when they were given placebo. In addition, the performance in the colour task of Stroops Colour Word Test performed after exercise was improved when BCAAs had been ingested during exercise, compared with the results from the placebo trial. There was no difference in the physical performance between the two trials measured as the amount of work done during the last 20 min of exercise when the subjects performed at their maximum. The plasma concentration ratio of free tryptophan/BCAAs, which increased by 45% during exercise and by 150% 5 min after exercise in the placebo trial, remained unchanged or even decreased when BCAAs were ingested.

  • 6.
    Blomstrand, Eva
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Eva Blomstrand's research group.
    Møller, K
    Secher, N H
    Nybo, L
    Effect of carbohydrate ingestion on brain exchange of amino acids during sustained exercise in human subjects.2005In: Acta Physiologica Scandinavica, ISSN 0001-6772, E-ISSN 1365-201X, Vol. 185, no 3, p. 203-9Article in journal (Refereed)
    Abstract [en]

    AIM: This study investigated the effect of prolonged exercise with and without carbohydrate intake on the brain exchange of amino acids, especially focussing on tryptophan and branched-chain amino acids (BCAA). METHODS: Five male subjects exercised for 3 h on a cycle ergometer at 200 +/- 7 W on two occasions; either supplemented with a 6% carbohydrate solution or with flavoured water (placebo). Catheters were inserted into the right internal jugular vein and the radial artery of the non-dominant arm. The brain exchange of amino acids during exercise was calculated from the arterial-jugular venous concentration difference multiplied by plasma flow. RESULTS: About 106 micromol (22 mg) of tryptophan was taken up by the brain during exercise in the placebo trial, whereas no significant uptake was observed in the carbohydrate trial. In accordance, the arterial concentration of free tryptophan increased from 12 +/- 1 to 20 +/- 2 micromol L(-1) during the placebo trial and was significantly higher compared with the glucose trial (14 +/- 1 micromol L(-1) at the end of exercise). Also, the arterial concentration of total tryptophan (free and albumin-bound) increased during the first 30 min of exercise in both trials, but returned to the basal level at 180 min of exercise. In both trials, BCAA were taken up by the brain while glutamine was released. CONCLUSION: The present data show that both tryptophan and BCAA are taken up by the brain during prolonged exercise, and we suggest that the cerebral uptake of tryptophan may relate to increased synthesis of serotonin (5-HT) in the brain.

  • 7. 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)
  • 8. 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.

  • 9. 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.

  • 10. Essén-Gustavsson, Birgitta
    et al.
    Blomstrand, Eva
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Eva Blomstrand's research group.
    Effect of exercise on concentrations of free amino acids in pools of type I and type II fibres in human muscle with reduced glycogen stores.2002In: Acta Physiologica Scandinavica, ISSN 0001-6772, E-ISSN 1365-201X, Vol. 174, no 3, p. 275-81Article in journal (Refereed)
    Abstract [en]

    A few animal studies have shown that some amino acid concentrations vary between different muscle fibre types. In the present study, amino acid concentrations were measured in separate pools of different fibre types in human skeletal muscle, with reduced glycogen stores, before and after sustained exercise. Five subjects exercised at a submaximal work rate for 60 min and then at a maximal rate for 20 min. Biopsy samples were taken from the vastus lateralis muscle before and after exercise; they were freeze-dried and individual fibres were dissected out. Fragments of these fibres were stained for myosin-adenosine triphosphatase (ATPase) and identified as type I or type II fibres. The concentrations of free amino acids were measured by high performance liquid chromatography (HPLC) in perchloric acid (PCA) extracts containing pools of either type of fibre. After exercise, glycogen was decreased in type I fibres (53%) and in four subjects also in type II fibres. The concentrations of most amino acids were similar in the two fibre types before exercise, but the glutamate, aspartate and arginine levels were 10% higher in type II than in type I fibres. After exercise, the glutamate concentration was decreased by 45% in both fibre types and the branched-chain amino acids (BCAA) were decreased in type II fibres (14%). Exercise caused an increase by 25-30% in tyrosine concentration in both type I and type II fibres. The results show that amino acids can be measured in pools of fibre fragments and suggest that amino acid metabolism play an important role in both type I and type II fibres during exercise.

  • 11. Fridén, Jan
    et al.
    Seger, Jan
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences.
    Ekblom, Björn
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Björn Ekblom's research group.
    Topographical localization of muscle glycogen: an ultrahistochemical study in the human vastus lateralis1989In: Acta Physiologica Scandinavica, ISSN 0001-6772, E-ISSN 1365-201X, Vol. 135, p. 381-391Article in journal (Refereed)
    Abstract [en]

    The fine structural pattern of glycogen storage in resting and sprint-exercised human vastus lateralis muscle fibres of different types was analysed using ultrahistochemical methods. Three male subjects (31-36 years) performed 60 consecutive, supramaximal bouts of bicycle exercise, each starting every 1 min and having a duration of 8 s (including approximately 3 s of acceleration). The load was estimated to correspond to 200% of VO2-max. Five other subjects (22-27 years) constituted controls. Ultrathin sections stained with periodic acid-thiosemicarbazide-silver proteinate (PA-TSC-SP) clearly revealed a compartmental distribution of glycogen. Glycogen is stored at five topographically, and probably also functionally, different locations. They are the subsarcolemmal, intermyofibrillar, para-Z-disc, N2-line, and H-zone spaces. During the exercise, glycogen from the N2-line and para-Z-disc locations is preferentially utilized. Serial sections stained with uranyl acetate and lead citrate demonstrated that glycogen stores of the type 2 fibres were more depleted than those of type 1 fibres. The implications of the differential intracellular glycogen storage are discussed

  • 12.
    Fuchi, Tokio
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences.
    Rosdahl, Hans
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences.
    Hickner, R C
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences.
    Ungerstedt, Urban
    Henricksson, Jan
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences.
    Microdialysis of rat skeletal muscle and adipose tissue: dynamics of the interstitial glucose pool.1994In: Acta Physiologica Scandinavica, ISSN 0001-6772, E-ISSN 1365-201X, Vol. 151, no 2, p. 249-60Article in journal (Refereed)
    Abstract [en]

    Microdialysis was evaluated as a method for studying glucose metabolism in skeletal muscle. Dialysis probes (0.5 x 10 mm) were perfused at 0.5 or 1.0 microliter min-1. Based upon perfusion with glucose, the muscle interstitial glucose concentration was estimated to be 6.9 +/- 0.3 mM (n = 14), which was not significantly different from the blood glucose level. With insulin infusion (1200 mU kg-1 body wt i.v.), the insulin-induced change in the glucose concentration of the interstitial space of muscle was of equal magnitude to that of blood and adipose tissue. In spite of this, when the perfusion medium was not supplemented with glucose, the glucose concentration decreased more in skeletal muscle dialysates (to 36.7 +/- 4.9% of the initial level) than in blood (to 29.7 +/- 5.0%) but less than in adipose tissue (to 17.7 +/- 4.9% of the initial level) (P < 0.05). The results indicate that these differences are due to tissue-specific differences in the dynamic balance between the supply to, and removal from, the interstitial glucose pool. This balance is revealed as a result of the constant glucose drainage by the microdialysis probe. The present results show that, in skeletal muscle, increases in glucose uptake occur with a concomitant increase in tissue blood flow as revealed by the microdialysis ethanol technique, whereas in adipose tissue the glucose uptake increases in the absence of a corresponding increase in blood flow.

  • 13. Grillner, S
    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.
    Intra-abdominal pressure changes during natural movements in man.1978In: Acta Physiologica Scandinavica, ISSN 0001-6772, E-ISSN 1365-201X, Vol. 103, no 3, p. 275-83Article in journal (Refereed)
    Abstract [en]

    The weight of the upper part of the trunk is partially transmitted to the pelvis via the vertebral column. If the muscle walls around the abdominal cavity are contracted, a high pressure can be generated within the cavity (greater than 200 mmHg). The abdominal space can them transmit part of weight to, e.g., the upper part of the body, Intra-abdominal pressure recordings have been performed during locomotion and other natural movements with intragastric pressure recordings. With each step, there is a phasic variation in pressure, with its peak coinciding with that of the peak vertical force exerted by the leg against the ground. The peak values increase progressively with the speed of walking/running up to a mean of 38 mmHg and with trough values of 16 mmHg. The phasic variations with each step is due to a phasic activation of the abdominal muscles, with an EMG activity starting 50 ms or more before foot contact. If an extra load is put on the back, the posture changes and at the highest speed of running the pressure values are significantly higher than without this additional load. After a jump down from a moderate height of 0.4 m, the average increase is 89 mmHg and can often exceed 100 mmHg. These pressure changes are large and will presumably act to unload the spine under the prevailing biomechanical conditions and, in addition, there will no doubt be an effect on the circulatory system.

  • 14.
    Hickner, R C
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences.
    Rosdahl, Hans
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences.
    Borg, Ingrid
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences.
    Ungerstedt, Urban
    Jorfeldt, Lennart
    Henriksson, Jan
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences.
    Ethanol may be used with the microdialysis technique to monitor blood flow changes in skeletal muscle: dialysate glucose concentration is blood-flow-dependent.1991In: Acta Physiologica Scandinavica, ISSN 0001-6772, E-ISSN 1365-201X, Vol. 143, no 3, p. 355-6Article in journal (Refereed)
  • 15.
    Hickner, R C
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences.
    Rosdahl, Hans
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences.
    Borg, Ingrid
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences.
    Ungerstedt, Urban
    Jorfeldt, Lennart
    Henriksson, Jan
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences.
    The ethanol technique of monitoring local blood flow changes in rat skeletal muscle: implications for microdialysis.1992In: Acta Physiologica Scandinavica, ISSN 0001-6772, E-ISSN 1365-201X, Vol. 146, no 1, p. 87-97Article in journal (Refereed)
    Abstract [en]

    We have investigated the feasibility of monitoring local skeletal muscle blood flow in the rat by including ethanol in the perfusion medium passing through a microdialysis probe placed in muscle tissue. Ethanol at 5, 55, or 1100 mM did not directly influence local muscle metabolism, as measured by dialysate glucose, lactate, and glycerol concentrations. The clearance of ethanol from the perfusion medium can be described by the outflow/inflow ratio ([ethanol]collected dialysate/[ethanol]infused perfusion medium), which was found to be similar (between 0.36 and 0.38) at all ethanol perfusion concentrations studied. With probes inserted in a flow-chamber, this ratio changed in a flow-dependent way in the external flow range of 5-20 microliters min-1. The ethanol outflow/inflow ratio in vivo was significantly (P less than 0.001) increased (to a maximum of 127 +/- 2.8% and 144 +/- 7.4% of the baseline, mean +/- SEM) when blood flow was reduced by either leg constriction or local vasopressin administration, and significantly (P less than 0.001) reduced (to 62 +/- 6.4% and 43 +/- 4.4% of baseline) with increases in blood flow during external heating or local 2-chloroadenosine administration, respectively. Dialysate glucose concentrations correlated negatively with the ethanol outflow/inflow ratio (P less than 0.01) and consequently decreased (to 46 +/- 7.6% and 56 +/- 5.6% of baseline) with constriction and vasopressin administration and increased (to 169 +/- 32.5% and 262 +/- 16.7% of baseline) following heating and 2-chloroadenosine administration. Dialysate lactate concentrations were significantly increased (approximately 2-fold, P less than 0.001) during all perturbations of blood flow. In conclusion, this technique makes it possible to monitor changes in skeletal muscle blood flow; however, methods of quantification remain to be established. The fact that blood flow changes were found to significantly affect interstitial glucose and lactate concentrations as revealed by microdialysis indicates that this information is critical in microdialysis experiments.

  • 16. Huang, Q-M
    et al.
    Andersson, Eva A
    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.
    Specific phase related patterns of trunk muscle activation during lateral lifting and lowering.2003In: Acta Physiologica Scandinavica, ISSN 0001-6772, E-ISSN 1365-201X, Vol. 178, no 1, p. 41-50Article in journal (Refereed)
    Abstract [en]

    AIM: Lateral bending of the trunk has been demonstrated to be a risk factor in connection with injuries to the spine and its surrounding tissues. Adequate co-ordination of muscle controlling movement and stabilization of the trunk is essential to avoid injury. However, little is yet known about the responses of the lumbar trunk muscles during lateral lifting and lowering. The present investigation was therefore designed to study these responses. METHODS: In six subjects performing lateral lifting and lowering of different loads (0-40 kg) held laterally in one hand, the activities of eight trunk muscles were recorded using intramuscular electrodes. In addition, the angular motion of the trunk from side to side was measured from video recordings. Electromyographic amplitudes on both the contra- and ipsi-lateral sides (ipsi = towards the loaded hand) were analysed in relation to defined phases of trunk motion. RESULTS: Three periods of trunk muscle activation were generally observed, two from the contralateral muscles at the beginning and end of the motion and one from the ipsilateral muscles during the mid-part of the motion. The activities of the contralateral muscles increased, whereas the activities of the ipsilateral muscles decreased with increasing load. The degree of bilateral co-activation was greater in ventral than in dorsal muscles, in lowering compared with lifting, and in no-load or low-load compared with heavy load conditions. CONCLUSION: The co-ordination of trunk muscle activations during side-to-side trunk movements is dependent on trunk position and load. It is speculated that ventral muscles, particularly the oblique and transverse abdominal muscles, are relatively more involved than the other trunk muscles in trunk stabilization, especially in connection with lowering of a light hand-held load.

  • 17. Hultén, B
    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
    Karlsson, J
    Relationship between isometric endurance and fibre types in human leg muscles.1975In: Acta Physiologica Scandinavica, ISSN 0001-6772, E-ISSN 1365-201X, Vol. 93, no 1, p. 135-8Article in journal (Refereed)
    Abstract [en]

    Relationship between isometric endurance performance at 50% of maximal voluntary isometric contraction (MCV) and skeletal muscle fibre composition has been elucidated in 19 physical education students. This was found to be linear and the equation corresponded to: y=9.35 + 1.093x; r=0.70 (endurance time expressed in seconds and fibre composition as percent slow twitch muscle fibres (ST) of the vastus lateralis muscle). As it is assumed from previous studies that similar isometric tensions preferentially recruit fast twitch muscle fibres (FT) and that the muscle at the point of exhaustion exhibits maximal values for lactate accumulation, it is suggested that lactate formed in FT fibres is released and stored in nonrecruited ST fibres. The ability to sustain similar isometric tension would then be depending on how large the fraction of ST fibres is that can serve as a lactaterecipient for lactate producing FT fibres.

  • 18. Häggmark, T
    et al.
    Thorstensson, Alf
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Fibre types in human abdominal muscles.1979In: Acta Physiologica Scandinavica, ISSN 0001-6772, E-ISSN 1365-201X, Vol. 107, no 4, p. 319-25Article in journal (Refereed)
    Abstract [en]

    Histochemical muscle fibre composition was studied in biopsied from the four different muscles of the abdominal wall (rectus abdominis, RA, obliquus externus, OE, obliquus internus, OI, and transversus abdominis, Tr) in 13 normal human subjects (9 females and 4 males, age 24-55 years) undergoing gall-bladder surgery. Muscle fibres were classified as Type I, IIA, IIB or IIC on the basis of their myofibrillar ATPases' pH lability. There were large inter-individual variations in fibre composition, whereas, in general, the differences between the different muscles were minor or non-existent. Mean fibre distribution ranges were 55-58% I, 15-23% 22A, 21-28% IIB, and 0-1% II C fibres. The least fibre diameters were similar for all types and muscles (range of means 50-54 micrometer) except for Tr in which the Type II fibres were smaller (mean 45 micrometer). There was a high correlation in the size of Type I vs. II fibres and Type IIA vs. IIB fibres in all layers. The oxidative potential (NADH-diaphorase staining intensity) appeared high in Type I fibres and low in Type II fibres, irrespective of subgroups. Thus, based on histochemical fibre composition, the different abdominal muscles appear to have a similar functional capacity. However, functional differences between individuals were indicated by the large inter-individual variation in muscle fibre distribution.

  • 19. Karlsson, J
    et al.
    Sjödin, B
    Thorstensson, Alf
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Hultén, B
    Frith, K
    LDH isozymes in skeletal muscles of endurance and strength trained athletes.1975In: Acta Physiologica Scandinavica, ISSN 0001-6772, E-ISSN 1365-201X, Vol. 93, no 2, p. 150-6Article in journal (Refereed)
    Abstract [en]

    Muscle biopsy samples were obtained from arm and leg muscles of endurance and strength trained athletes, respectively. Total LDH activity as well as occurrence and activity of LDH isozymes were determined. Comparing the results from the athletes with those from non-trained subjects with corresponding fibre compositions, it was found that the endurance athletes had a lower total LDH activity, a higher relative activity of the most heart-specific isozymes. LDH (1 + 2), and, on electrophoretic separation, a complete absence of LDH (4 + 5) in both arm and leg muscles. As compared to the untrained material the strength trained athletes tended to have a higher total LDH activity, a similar distribution of relative isozyme activities, and, in the leg muscles, a strong electrophoretic band corresponding to LDH 5, the most skeletal muscle specific isozyme.

  • 20. Komi, P V
    et al.
    Viitasalo, J H
    Havu, M
    Thorstensson, Alf
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Sjödin, B
    Karlsson, J
    Skeletal muscle fibres and muscle enzyme activities in monozygous and dizygous twins of both sexes.1977In: Acta Physiologica Scandinavica, ISSN 0001-6772, E-ISSN 1365-201X, Vol. 100, no 4, p. 385-92Article in journal (Refereed)
    Abstract [en]

    Significance of the genetic component in determining the interindividual variation observed in skeletal muscle fibre composition and enzyme activities was investigated in 31 pairs of male and female monozygous (MZ) and dizygous (DZ) twins, whose ages ranged in all but one pair (11 years) from 15 to 24 years. Percent distribution of slow twitch muscle fibres and activities of Ca2+ and Ng2+ stimulated ATPases, creatine phosphokinase, myokinase, phosphorylase, lactate dehydrogenase (LDH) and distribution of its isozyme LDH-1 were all analyzed in biopsy samples taken from the vastus lateralis muscle. The data disclosed that in contrast to DZ twins the MZ twins of both sexes had an essentially identical muscle fibre composition. Calculation of the heritability estimate for this parameter gave the values of 99.5% and 92.8%, respectively for males and females. In contrast to the fibre composition presence of a significant genetic component was not observed in any of the enzyme activities studied. It was concluded that there is a predominant genetic influence on the skeletal muscle fibre composition in man, and thus also on the potential capacity of the muscles to perform work.

  • 21. Löscher, W N
    et al.
    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.
    Electromyographic responses of the human triceps surae and force tremor during sustained submaximal isometric plantar flexion.1994In: Acta Physiologica Scandinavica, ISSN 0001-6772, E-ISSN 1365-201X, Vol. 152, no 1, p. 73-82Article in journal (Refereed)
    Abstract [en]

    The objective was to investigate electromyographic activity (EMG) and isometric force tremor (IFT) changes during a sustained sub-maximal isometric contraction in two muscles acting upon the same joint but differing in muscle fibre composition. Surface and intra-muscular EMG activity from the gastrocnemius and soleus muscles and IFT were recorded during an exhausting isometric plantar flexion (30% of maximal voluntary contraction). Surface EMG amplitude (RMS) of both gastrocnemius and soleus muscles increased significantly over time. Gastrocnemius EMG RMS increased in a non-linear fashion while soleus EMG RMS increased linearly. A significant linear decrease of surface EMG mean power frequency (MPF) was observed over time for both muscles. The decrease in gastrocnemius MPF was significantly greater than that for soleus. Intra-muscular EMG results showed similar trends. Correlations of intramuscular EMG RMS and MPF with time were, however, characterized by lower correlation coefficients than those from the surface EMG. Isometric force tremor RMS significantly increased non-linearly with duration of contraction, while IFT MPF showed a significant linear decrease with time. Changes in surface EMG RMS were correlated to changes seen in IFT RMS, in particular, for the predominantly fast twitch gastrocnemius muscle. Correlation coefficients of surface EMG MPF and IFT MPF were lower than RMS correlations. The associated changes in IFT and EMG with fatigue indicate alterations in motor unit firing rate, recruitment and synchronization. The muscle specificity of the EMG and IFT changes suggests a coupling to muscle fibre type composition, although differences in the relative force contribution of each muscle could also affect the results.

  • 22. Malm, Christer
    et al.
    Ekblom, Örjan
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Björn Ekblom's research group.
    Ekblom, Björn
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Björn Ekblom's research group.
    Immune system alteration in response to two consecutive soccer games.2004In: Acta Physiologica Scandinavica, ISSN 0001-6772, E-ISSN 1365-201X, Vol. 180, no 2, p. 143-55Article in journal (Refereed)
    Abstract [en]

    AIM: Changes in leucocyte and monocyte subpopulations were investigated in 10 elite male soccer players aged 16-19 years. The purpose was to perform a descriptive study of immunological alterations in elite soccer players in response to two consecutive games separated by 20 h. It was hypothesized that in response to two games the players would show signs of short-term immunosuppression. METHODS: Blood samples were taken before the first soccer game, immediately after the second game and after 6, 24, 48 and 72 h. Cell surface antigens, testosterone and cortisol were investigated. RESULTS: During the first 6 h after the second game there was a significant increase in number of circulating neutrophils, mature (CD20+ CD5+) B cells and CD4/CD8 ratio. A significant decrease was observed in the number of natural killer (NK) cells, monocytes and adhesion on lymphocytes and monocytes. In a delayed phase, 48 h after the second game the expression of both adhesion and signalling molecules increased on lymphocytes and monocytes. Changes in adhesion and signalling molecules at 48 h correlated negatively to the subjects VO2max, suggesting larger immunological response to similar exercise in subjects with lower aerobic exercise capacity. CONCLUSION: In response to competitive soccer exercise some immunological variables are enhanced while others are depressed. Observed changes may serve a purpose in adaptation to exercise by signalling via adhesion.

  • 23. Mogensen, Martin
    et al.
    Sahlin, Kent
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Research group for Mitokondriell funktion och metabolisk kontroll.
    Mitochondrial efficiency in rat skeletal muscle: influence of respiration rate, substrate and muscle type.2006In: Acta Physiologica Scandinavica, ISSN 0001-6772, E-ISSN 1365-201X, Vol. 185, p. 229-236Article in journal (Refereed)
    Abstract [en]

    Aim: To investigate the hypothesis that mitochondrial efficiency (i.e. P/O ratio) is higher in type I than in type II fibres during submaximal rates of respiration.

    Methods: Mitochondria were isolated from rat soleus and extensor digitorum longus (EDL) muscles, representing type I and type II fibres, respectively. Mitochondrial efficiency (P/O ratio) was determined with pyruvate (Pyr) or palmitoyl-L-carnitine (PC) during submaximal (constant rate of ADP infusion) and maximal (Vmax, state 3) rates of respiration and fitted to monoexponential functions.

    Results: There was no difference in Vmax between PC and Pyr in soleus but in EDL Vmax with PC was only 58% of that with Pyr. The activity of 3-hydroxyacyl-CoA dehydrogenase (HAD) was 3-fold higher in soleus than in EDL. P/O ratio at Vmax was 8-9% lower with PC (2.33±0.02 (soleus) and 2.30±0.02 (EDL)) than with Pyr (2.52±0.03 (soleus) and 2.54±0.03 (EDL)) but not different between the two muscles (P>0.05). P/O ratio was low at low rates of respiration and increased exponentially when the rate of respiration increased. The asymptotes of the curves were similar to P/O ratio at Vmax. P/O ratio at submaximal respirations was not different between soleus and EDL neither with Pyr nor with PC.

    Conclusion: Mitochondrial efficiency, as determined in vitro, was not significantly different in the two fibre types neither at Vmax nor at submaximal rates of respiration. The low Vmax for PC oxidation in EDL may relate to low activity of β-oxidation.

  • 24. Moritani, T
    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.
    Differences in modulation of the gastrocnemius and soleus H-reflexes during hopping in man.1990In: Acta Physiologica Scandinavica, ISSN 0001-6772, E-ISSN 1365-201X, Vol. 138, no 4, p. 575-6Article in journal (Refereed)
  • 25. Moritani, T
    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.
    Astrand, P O
    Swedish School of Sport and Health Sciences, GIH.
    Neural and biomechanical differences between men and young boys during a variety of motor tasks.1989In: Acta Physiologica Scandinavica, ISSN 0001-6772, E-ISSN 1365-201X, Vol. 137, no 3, p. 347-55Article in journal (Refereed)
    Abstract [en]

    The adaptation in activation patterns of the ankle extensor muscles to different functional demands was studied in adult men (n = 10) and 9-year-old boys (n = 10). The relative magnitude of the activation of the slow soleus (SOL) and the relatively fast medial gastrocnemius (MG) muscle was measured during various postures and hopping tasks on a force plate. In addition, the myo-electric activity was quantified in three different phases of the stretch-shortening cycles during hopping. Major differences between boys and adults were observed in the postural tasks, where the boys appeared to utilize the MG to a relatively larger extent. During maximal height hopping there was a clearly larger potentiation of the MG activity in the adults, particularly in the eccentric phase. On the other hand, there were striking similarities between boys and adults with respect to the degree of pre-activation of both muscles during the different hopping regimes as well as potentiation of muscle activity during the concentric phase of maximal height hopping. Thus, some aspects of the selective neural control of the ankle extensor muscles appear to be manifested in pre-pubertal boys. However, the data also indicate that other factors, such as utilization of stored elastic energy in the muscles and stretch reflex potentiation, will still continue to develop from the age of nine.

  • 26. Nie, Z T
    et al.
    Lisjö, S
    Åstrand, PO
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences.
    Henriksson, J
    In-vitro stimulation on the rat epitrochlearis muscle. II. Effects of catecholamines and nutrients on protein degradation and amino acid metabolism.1989In: Acta Physiologica Scandinavica, ISSN 0001-6772, E-ISSN 1365-201X, Vol. 135, no 4, p. 523-9Article in journal (Refereed)
    Abstract [en]

    The influence of catecholamines and branched-chain amino acids (BCAA) plus insulin on protein degradation and amino acid metabolism was investigated in isolated and electrically stimulated rat epitrochlearis muscles. 10(-7) M adrenaline significantly increased the total amount of muscle tyrosine during 40 min of stimulation with 50 Hz (I s min 1) pulse trains. On the other hand, BCAA + insulin at normal and five times normal plasma concentrations had no effect on muscle tyrosine. Muscle 3- methylhistidine was not influenced by any of the treatments. Muscle release and content of aspartate, alanine, glutamate and glutamine showed individual response characteristics to catecholamines and BCAA + insulin. The data indicate that adrenaline can induce an increased total protein degradation in rat fast muscle during acute contractions in vitro and, furthermore, that BCAA + insulin does not retard protein breakdown during acute muscle contraction.

  • 27.
    Nilsson, Johnny
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Tesch, P
    Thorstensson, Alf
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Fatigue and EMG of repeated fast voluntary contractions in man.1977In: Acta Physiologica Scandinavica, ISSN 0001-6772, E-ISSN 1365-201X, Vol. 101, no 2, p. 194-8Article in journal (Refereed)
    Abstract [en]

    A fatigue test consisting of repeated fast maximal contractions of the left quadriceps muscle in an isokinetic apparatus was performed by 12 healthy male subjects (19-25 yrs). EMG signals recorded from the surface of the left vastus lateralis muscle, from which also biopsies were obtained for muscle fibre classification. Only minor changes were observed in the EMG variables despite a decrease in muscle strength performance, in terms of peak torque, work and power to about 50% of initial values after 100 contractions. The concomitantly obtained positive correlation between the increase in EMG/torque ratio and the individual percentage of fast twitch (FT) muscle fibres indicated that local factors in the muscle, primarily in FT fibres, were causing the development of fatigue during repeated dynamic contractions with high power outputs.

  • 28.
    Nilsson, Johnny
    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.
    Adaptability in frequency and amplitude of leg movements during human locomotion at different speeds.1987In: Acta Physiologica Scandinavica, ISSN 0001-6772, E-ISSN 1365-201X, Vol. 129, no 1, p. 107-14Article in journal (Refereed)
    Abstract [en]

    In this study of human locomotion we investigate to what extent the normal frequency and amplitude of leg movements can be modified voluntarily at different constant velocities, and how these modifications are accomplished in terms of changes in duration and length of the support and swing phases of the stride cycle. Eight healthy male subjects performed walking and running on a motor-driven treadmill at speeds ranging from 1.0 to 3.0 m s-1 (walking) and 1.5 to 8.0 m s-1 (running), respectively. At each speed the subjects walked and ran with: normal stride frequency; the highest possible stride frequency, and the lowest possible stride frequency. Time for foot contact was measured with a special pressure transducer system under the sole of each shoe. At all speeds of walking and running it was possible to either increase or decrease the frequency of leg movements; that is, to decrease or increase stride cycle duration. The range of variation decreased with increasing speed. The mean overall stride frequency range was 0.41 (low frequency walk 1.0 m s-1)-3.57 Hz (high-frequency run 1.5 m s-1). Stride length ranged 0.40 (high frequency walk 1.0 m s-1)-5.00 m (low frequency run 6.0 m s-1). At normal frequency the overall ranges of stride frequency and length were 0.83-1.95 Hz and 1.16-4.10 m, respectively. The stride frequency increased with speed in low frequency walking and running (as in normal frequency) and decreased in high frequency, despite the effort to maintain extreme frequencies. Only in high frequency walking could the stride frequency be kept approximately constant.(ABSTRACT TRUNCATED AT 250 WORDS)

  • 29.
    Nilsson, Johnny
    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.
    Ground reaction forces at different speeds of human walking and running.1989In: Acta Physiologica Scandinavica, ISSN 0001-6772, E-ISSN 1365-201X, Vol. 136, no 2, p. 217-27Article in journal (Refereed)
    Abstract [en]

    In this study the variation in ground reaction force parameters was investigated with respect to adaptations to speed and mode of progression, and to type of foot-strike. Twelve healthy male subjects were studied during walking (1.0-3.0 m s-1) and running (1.5-6.0 m s-1). The subjects were selected with respect to foot-strike pattern during running. Six subjects were classified as rearfoot strikers and six as forefoot strikers. Constant speeds were accomplished by pacer lights beside an indoor straightway and controlled by means of a photo-electronic device. The vertical, anteroposterior and mediolateral force components were recorded with a force platform. Computer software was used to calculate durations, amplitudes and impulses of the reaction forces. The amplitudes were normalized with respect to body weight (b.w.). Increased speed was accompanied by shorter force periods and larger peak forces. The peak amplitude of the vertical reaction force in walking and running increased with speed from approximately 1.0 to 1.5 b.w. and 2.0 to 2.9 b.w. respectively. The anteroposterior peak force and mediolateral peak-to-peak force increased about 2 times with speed in walking and about 2-4 times in running (the absolute values were on average about 10 times smaller than the vertical). The transition from walking to running resulted in a shorter support phase duration and a change in the shape of the vertical reaction force curve. The vertical peak force increased whereas the vertical impulse and the anteroposterior impulses and peak forces decreased. In running the vertical force showed an impact peak at touch-down among the rearfoot strikers but generally not among the forefoot strikers. The first mediolateral force peak was laterally directed (as in walking) for the rearfoot strikers but medially for the forefoot strikers. Thus, there is a change with speed in the complex interaction between vertical and horizontal forces needed for propulsion and equilibrium during human locomotion. The differences present between walking and running are consequences of fundamental differences in motor strategies between the two major forms of human progression.

  • 30.
    Nilsson, Johnny
    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.
    Halbertsma, J
    Changes in leg movements and muscle activity with speed of locomotion and mode of progression in humans.1985In: Acta Physiologica Scandinavica, ISSN 0001-6772, E-ISSN 1365-201X, Vol. 123, no 4, p. 457-75Article in journal (Refereed)
    Abstract [en]

    Knowledge of adaptations to changes in speed and mode of progression (walking-running) in human locomotion is important for an understanding of underlying neural control mechanisms and allows a comparison with more detailed animal studies. Leg movements and muscle activity patterns were studied in ten healthy males (19-29 yr) during level walking (0.4-3.0 m X s-1) and running (1.0-9.0 m X s-1) on a motor-driven treadmill. Movements were recorded in the sagittal plane with a Selspot optoelectronic system. Recordings of EMG were made from seven different muscles of one leg by means of surface electrodes. Durations, amplitudes and relative phase relationships of angular displacements and EMG activity were analysed in relation to different phases of the stride cycle (defined by the leg movements). The durations of the entire stride cycle and of the support phase were found to decrease curvilinearly with velocity. Swing and support phase durations were linearly related to cycle duration in walking, and curvilinearly related in running. The characteristic occurrence of double support phases in walking was also seen in very slow running. Support length increased with speed up to about 1.2 m both in walking and running, but was longer in walking at the same velocity. Increases in net angular displacements were largest for hip movements and for knee flexion-extension during the swing phase in running. With increasing velocity a clear shift in relative rectus femoris activity occurred from knee extension to hip flexion. Gastrocnemius lateralis (LG) was co-activated with the other leg extensors prior to foot contact in running, whereas in walking LG was not turned on until later in the support phase. The ankle flexor tibialis anterior had its main peak of activity after touch-down in walking and before touch-down in running. The same basic structure of the stride cycle as in other animals suggests similarities in the underlying neural control. Human speed adaptation is distinguished primarily by an increase in both frequency and amplitude of leg movements and by a possibility of changing between a walking and a running type of movement pattern.

  • 31. Oddsson, L
    et al.
    Thorstensson, Alf
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Fast voluntary trunk flexion movements in standing: motor patterns.1987In: Acta Physiologica Scandinavica, ISSN 0001-6772, E-ISSN 1365-201X, Vol. 129, no 1, p. 93-106Article in journal (Refereed)
    Abstract [en]

    The electromyographical (EMG) activity was studied during voluntary flexion movements of the trunk in erect standing man. The movements were performed at maximal velocity with successively increasing amplitude to cover the whole range of motion. The EMG activity was recorded from agonist-antagonist pairs of muscles at the ankle, knee, hip and trunk. The angular displacements at the corresponding joints were recorded using a Selspot optoelectronic system. The duration of initiating activity in prime movers (rectus abdominis and rectus femoris) as well as time to onset of activity in muscles braking the primary movement (erector spinae, gluteus maximus and hamstrings) were highly correlated with amplitude, duration, peak velocity and time to peak velocity of the movement (r = 0.59-0.91). The corresponding correlations for peak acceleration and deceleration of the movement were low (r = 0.03-0.38), indicating that acceleration and deceleration of a movement was not coded in the temporal aspects of the EMG. Onset of activity in rectus abdominis and rectus femoris as well as an early appearing burst of activity in vastus lateralis were invariant in relation to start of movement over the whole movement range. In the initial phase of a fast trunk flexion, activity in tibialis anterior appeared successively earlier with increasing movement amplitude. This resulted in a changed order of activation for the muscles from proximal to distal (rectus abdominis first) to distal to proximal (tibialis anterior first). Two different forms of associated postural adjustments are present during a fast trunk flexion, one early fast knee flexion and a later slower angle extension. Prior to knee flexion, no activity was recorded from muscles flexing at the knee implying that some other force must create a flexing torque around the knee. It is suggested that activity in rectus abdominis initiating the primary movement also initiates knee flexion through the upward pulling of pelvis. This would be possible since rectus femoris stabilizes the pelvis in relation to the leg, allowing the force in rectus abdominis to be transmitted below the hip joint and act extending around the ankle joint. However, when tibialis anterior is activated it stabilizes the shank which in turn will cause a knee flexion controlled by a lengthening contraction in vastus lateralis. During the subsequent ankle extension activity appears in lateral gastrocnemius and soleus causing the associated postural adjustment at the ankle. It can be concluded that activation of postural muscles prior to prime mover muscles is not always necessary.(ABSTRACT TRUNCATED AT 400 WORDS)

  • 32. Oddsson, L
    et al.
    Thorstensson, Alf
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Fast voluntary trunk flexion movements in standing: primary movements and associated postural adjustments.1986In: Acta Physiologica Scandinavica, ISSN 0001-6772, E-ISSN 1365-201X, Vol. 128, no 3, p. 341-9Article in journal (Refereed)
    Abstract [en]

    Movement patterns were studied during fast voluntary forward flexions of the trunk from an erect standing position. Three healthy subjects performed three series of six consecutive trunk flexions at maximum velocity and with successively increasing amplitude, covering a major part of the range of motion (range for all subjects: 13-97 degrees). Angular displacements of the trunk, hip, knee and ankle were measured together with the tilt of the pelvis and the flexion of the spine using a Selspot optoelectronic system. Trunk flexion was the result of a simultaneous forward pelvic tilt and flexion of the spine. For trunk movements up to 55 degrees, spine flexion dominated the movement, whereas for larger movements a major part of the amplitude was caused by pelvic tilt. During flexion of the trunk a simultaneous hip flexion and ankle extension was seen. At the knee there was an initial flexion and a subsequent extension. The net amplitude of the knee flexion showed a negative correlation with net trunk flexion amplitude for movements up to 50 degrees, whereas for larger amplitudes the correlation was positive. Time from onset of the trunk movement to peak knee flexion showed a weak correlation to net trunk flexion amplitude (r = 0.34) whereas the corresponding correlation was higher for pelvic tilt, spine flexion, hip flexion, ankle extension, and knee extension (r = 0.60-0.91). Each successive trial during a series of trunk movements was started from an increasing degree of knee flexion. This gradual adaptation was also present when successive trunk flexions were performed with constant movement amplitude.(ABSTRACT TRUNCATED AT 250 WORDS)

  • 33. Oddsson, L
    et al.
    Thorstensson, Alf
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Task specificity in the control of intrinsic trunk muscles in man.1990In: Acta Physiologica Scandinavica, ISSN 0001-6772, E-ISSN 1365-201X, Vol. 139, no 1, p. 123-31Article in journal (Refereed)
    Abstract [en]

    The human trunk is a complex mechanical system comprised of large and small segments interconnected with several layers of muscles. An accurate control of this system is important during a variety of everyday tasks such as voluntary movements of the trunk, walking and running. This study was designed to investigate the interaction between muscles controlling the pelvis and the trunk during a variety of movements requiring a finely tuned coordination. Four subjects carried out seven different forms of fast oscillatory movements of the pelvis and trunk in the sagittal and transverse planes. Electromyographical activity (EMG) was recorded with surface electrodes from the abdominal muscles rectus abdominis (RA), obliquus externus (OE), obliquus internus (OI), and erector spinae (ES), from the hip flexor muscle rectus femoris (RF), the hip extensor muscle gluteus maximus (GM) and from the hip extensor/knee flexor muscles of the hamstrings group (HAM). Movements were recorded with an optoelectronic system (Selspot). The results indicate that during spontaneous flexion-extension movements of the trunk there was a basic alternating activation between a pure flexor (RF-RA-OE-OI) and an extensor synergy (ES-GM-HAM). Different mixed synergies appeared when more specific patterns of coordination of the pelvis and spine were performed. For example, during pelvic tilts in the sagittal plane, RA-OE-OI-GM formed a synergy which was activated reciprocally with ES. The neural circuitry controlling muscles of the pelvis and trunk is apparently adaptable to a variety of different tasks. Individual muscles were shown to either cause, brake or prevent a movement and to be integrated in several different task-specific motor synergies.(ABSTRACT TRUNCATED AT 250 WORDS)

  • 34.
    Rosdahl, Hans
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences.
    Samuelsson, A C
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences.
    Ungerstedt, Urban
    Henriksson, Jan
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences.
    Influence of adrenergic agonists on the release of amino acids from rat skeletal muscle studied by microdialysis.1998In: Acta Physiologica Scandinavica, ISSN 0001-6772, E-ISSN 1365-201X, Vol. 163, no 4, p. 349-60Article in journal (Refereed)
    Abstract [en]

    The microdialysis technique was used to study the effects of adrenergic agonists on the release of amino acids from rat skeletal muscle. The release was monitored indirectly by measurements of interstitial concentrations. To distinguish metabolic from vasoactive effects, the adrenaline and isoprenaline results were compared with those of vasopressin, alpha-agonists and adenosine. As determined by the microdialysis ethanol technique, adrenaline, alpha-agonists and vasopressin induced vasoconstriction, whereas isoprenaline and adenosine induced vasodilatation. The lactate-to-pyruvate ratio increased fourfold with adrenaline (P < 0.001) and by 54% with isoprenaline (P < 0.05), whereas no change was observed with alpha-agonists and adenosine. Vasopressin induced a fivefold increase in the lactate-to-pyruvate ratio (P < 0.001), but with an unchanged pyruvate concentration, indicating that the effect may have been secondary to ischaemia. Adrenaline induced a twofold and vasopressin a 34% increase in the concentration of alanine (P < 0.001), whereas isoprenaline, adenosine and alpha-agonists had no significant effect. Adrenaline-perfusion induced an initial anabolic effect as evidenced by a reduced concentration of tyrosine. A significant decrease in the glutamate-to-glutamine ratio was observed with adrenaline and isoprenaline (22 and 27%, P < 0.01) whereas alpha-agonists, vasopressin and adenosine were without effect. In conclusion, the present study showed that adrenaline, via a beta-adrenergically mediated activation of glycogenolysis, possibly further stimulated by ischaemia, induced an increased release of alanine from skeletal muscle. The study indicates a beta-adrenergic stimulation on the glutamine synthetase step and a short lasting anabolic effect of adrenaline. Differences in the magnitude of the effects of adrenaline and isoprenaline could be related to their different vasoactive properties.

  • 35.
    Rosdahl, Hans
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences.
    Ungerstedt, Urban
    Henriksson, Jan
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences.
    Microdialysis in human skeletal muscle and adipose tissue at low flow rates is possible if dextran-70 is added to prevent loss of perfusion fluid.1997In: Acta Physiologica Scandinavica, ISSN 0001-6772, E-ISSN 1365-201X, Vol. 159, no 3, p. 261-2Article in journal (Refereed)
  • 36.
    Schantz, Peter
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences.
    Capillary supply in heavy-resistance trained non-postural human skeletal muscle1983In: Acta Physiologica Scandinavica, ISSN 0001-6772, E-ISSN 1365-201X, Vol. 117, p. 153.155-Article in journal (Refereed)
  • 37.
    Schantz, Peter
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences.
    Capillary supply in hypertrophied human skeletal muscle1982In: Acta Physiologica Scandinavica, ISSN 0001-6772, E-ISSN 1365-201X, Vol. 114, p. 635-637Article in journal (Refereed)
  • 38.
    Schantz, Peter
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences.
    Dhoot, Gurtej
    Coexistence of slow and fast isoforms of contractile and regulatory proteins in human skeletal muscle fibres induced by endurance training1987In: Acta Physiologica Scandinavica, ISSN 0001-6772, E-ISSN 1365-201X, Vol. 131, p. 147-154Article in journal (Refereed)
  • 39.
    Schantz, Peter
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences.
    Henriksson, Jan
    Enzyme levels of NADH shuttle systems: measurements in isolated muscle fibres from humans of differing physical activity1987In: Acta Physiologica Scandinavica, ISSN 0001-6772, E-ISSN 1365-201X, Vol. 129, p. 505-515Article in journal (Refereed)
  • 40.
    Schantz, Peter
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences.
    Moritani, Toshio
    Karlson, Eddy
    Johansson, Eva
    Lundh, Anna
    Maximal voluntary force of bilateral and unilateral leg extension1989In: Acta Physiologica Scandinavica, ISSN 0001-6772, E-ISSN 1365-201X, Vol. 136, p. 185-192Article in journal (Refereed)
  • 41.
    Schantz, Peter
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences.
    Randall Fox, Emily
    Norgren, Peter
    Tydén, Anders
    The relationship between the mean muscle fibre area and the muscle cross-sectional area of the thigh in subjects with large differences in thigh girth1981In: Acta Physiologica Scandinavica, ISSN 0001-6772, E-ISSN 1365-201X, Vol. 113, p. 537-539Article in journal (Refereed)
  • 42.
    Schantz, Peter
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences.
    Randall-Fox, Emily
    Hutchison, Wallace
    Tydén, Anders
    Åstrand, Per-Olof
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences.
    Muscle fibre type distribution, muscle cross-sectional area and maximal voluntary strength in humans1983In: Acta Physiologica Scandinavica, ISSN 0001-6772, E-ISSN 1365-201X, Vol. 117, p. 219-226Article in journal (Refereed)
  • 43.
    Schantz, Peter
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences.
    Sjöberg, Berit
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences.
    Svedenhag, Jan
    Malate-aspartate and alpha-glycerophophate shuttle enzyme levels in human skeletal muscle: methodological considerations and effect of endurance training1986In: Acta Physiologica Scandinavica, ISSN 0001-6772, E-ISSN 1365-201X, Vol. 128, p. 397-407Article in journal (Refereed)
  • 44.
    Schantz, Peter
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences.
    Sjöberg, Berit
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences.
    Widebeck, Ann-Marie
    Ekblom, Björn
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences.
    Human skeletal muscle of trained and untrained paraplegics and tetraplegics1997In: Acta Physiologica Scandinavica, ISSN 0001-6772, E-ISSN 1365-201X, no 161, p. 31-39Article in journal (Refereed)
  • 45.
    Seger, Jan
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences.
    Thorstensson, Alf
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Electrically evoked eccentric and concentric torque-velocity relationships in human knee extensor muscles.2000In: Acta Physiologica Scandinavica, ISSN 0001-6772, E-ISSN 1365-201X, Vol. 169, p. 63-69Article in journal (Refereed)
    Abstract [en]

    The torque-velocity relationship, obtained during in situ conditions in humans, demonstrates a levelling-off of eccentric torque output at the isometric torque level, at least for knee extensor actions. In contrast, the in vitro force-velocity relationship for animal muscle preparations is characterized by a sharp rise in eccentric force from isometric maximum. A force-regulating 'protective' mechanism has been suggested during maximal voluntary high-tension eccentric muscle actions. To investigate this phenomenon, maximal voluntary and three different levels of submaximal, electrically induced torques were compared during isometric and low velocity (10, 20 and 30 degrees s-1) isokinetic eccentric and concentric knee extensor actions in 10 healthy, moderately trained subjects. Eccentric torque was higher than isometric during electrically evoked, but not during maximal voluntary muscle actions. In contrast, concentric torque was significantly lower than isometric for both maximal voluntary and submaximal, electrically evoked conditions. Comparisons of normalized torques (isometric value under each condition set to 100%) demonstrated that the maximal voluntary eccentric torque had to be increased by 20%, and the isometric by 10% in order for the maximal voluntary torque-velocity curve to coincide with the electrically stimulated submaximal ones. These results support the notion that a tension-regulating mechanism is present primarily during eccentric maximal voluntary knee extensor actions.

  • 46. Sjödin, B
    et al.
    Thorstensson, Alf
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Frith, K
    Karlsson, J
    Effect of physical training on LDH activity and LDH isozyme pattern in human skeletal muscle.1976In: Acta Physiologica Scandinavica, ISSN 0001-6772, E-ISSN 1365-201X, Vol. 97, no 2, p. 150-7Article in journal (Refereed)
    Abstract [en]

    Total lactate dehydrogenase (LDH) activity and LDH isozyme pattern were studied in muscle biopsies obtained from m. vastus lateralis after 1) "aerobic" training performed as interval and extreme distance running, respectively (3 subjects); and 2) "anaerobic" training for two months, carried out as repeated maximal bursts of approximately 1 min running (6 subjects). After the "anaerobic training" no changes in LDH properties could be detected, although running performance improved. The extreme distance running resulted in a decrease in total LDH activity and an increase in relative activity of the heart specific isozymes. A relationship was also shown between the relative activity of these isozymes and the training distance covered. The relatively more aerobic prevailing during distance running as compared to "anaerobic training" were proposed to decrease muscle specific subunits and/or increase synthesis of heart specific subunits in both muscle fiber types. This suggestion was supported by isozyme analysis of lyophilized and dissected single muscle fibres.

  • 47. Svensson, Michael B
    et al.
    Ekblom, Björn
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Björn Ekblom's research group.
    Cotgreave, Ian A
    Norman, Barbara
    Sjöberg, Berit
    Ekblom, Örjan
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Björn Ekblom's research group.
    Sjödin, Bertil
    Sjödin, Anders
    Adaptive stress response of glutathione and uric acid metabolism in man following controlled exercise and diet.2002In: Acta Physiologica Scandinavica, ISSN 0001-6772, E-ISSN 1365-201X, Vol. 176, no 1, p. 43-56Article in journal (Refereed)
    Abstract [en]

    Ergometer cycling performance as well as acute exercise-induced changes in the metabolism of energy-intermediates and glutathione (GSH) were investigated in skeletal muscle (SM) of 15 healthy young male subjects (VO(2max) approximately 54.7 mL kg(-1) min(-1), age approximately 25 years), before and after 3 days of controlled 'ìoverload-training' in combination with either high (62% of energy intake) or low (26% of energy intake) dietary intake of carbohydrates. The intake of a carbohydrate-rich diet clearly reduced the depletion of SM glycogen following the short-term training period, paralleled with a positive effect on the endurance performance, but not on high-intensity work-performance. An 'delayed over-reaching effect', defined as impaired work-performance, was observed after 2.5 days of recovery from the short-term training period, irrespective of the carbohydrate content of the diet and basal glycogen level in SM. Taken together, the main and novel findings of present investigation are: (1) an acute decrease of reduced GSH content and altered thiol-redox homeostasis in SM induced by strenuous high-intensity exercise; (2) an adaptive elevation of basal GSH level following the short-term training period; (3) an adaptive decrease of basal GSH level following 2.5 days recovery from training; (4) evidence of a relationship between the SM fibre type, physical performance capacity and GSH turnover during acute bouts of exercise; and (5) no evident effect of the level of carbohydrate intake on metabolism of GSH or energy intermediates. Furthermore, the induction of acute oxidative stress in exercising human SM and the adaptive responses to training are suggested to provide a protective antioxidant phenotype to the exercising SM during periods with repeated intense intermittent training.

  • 48. Tesch, P
    et al.
    Sjödin, B
    Thorstensson, Alf
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Karlsson, J
    Muscle fatigue and its relation to lactate accumulation and LDH activity in man.1978In: Acta Physiologica Scandinavica, ISSN 0001-6772, E-ISSN 1365-201X, Vol. 103, no 4, p. 413-20Article in journal (Refereed)
    Abstract [en]

    The lactate concentration in different muscle fibre types was determined in biopsy specimens from human vastus lateralis muscle after 30 and 60 s of maximal dynamic leg exercise. In addition, muscle fibre type distribution, total lactate dehydrogenase (LDH) activity, and isozymes of LDH were determined. In accordance with previous studies (Thorstensson and Karlsson 1976, Nilsson et al. 1977) it was found that an increasing proportion of slow twitch (ST) fibres corresponded to better sustained muscle force. Lactate was found preferentially in fast twitch (FT) fibres after 30 s, but after 60 s this difference was abolished. Differences between the two main muscle fibre types in muscle lactate, total LDH activity, and M-LDH activity were correlated to muscle fatigue. It was concluded that lactate or associated pH changes primarily in FT fibres could be one factor responsible for the impaired muscle function.

  • 49.
    Thorstensson, Alf
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Observations on strength training and detraining.1977In: Acta Physiologica Scandinavica, ISSN 0001-6772, E-ISSN 1365-201X, Vol. 100, no 4, p. 491-3Article in journal (Refereed)
  • 50.
    Thorstensson, Alf
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Carlson, H
    Fibre types in human lumbar back muscles.1987In: Acta Physiologica Scandinavica, ISSN 0001-6772, E-ISSN 1365-201X, Vol. 131, no 2, p. 195-202Article in journal (Refereed)
    Abstract [en]

    The distribution of histochemically identified muscle fibre types was studied in biopsy samples from the two main muscles in the lumbar region of the human erector spinae, the multifidus and the longissimus, in 16 healthy subjects (nine males and seven females, age 20-30 years). Muscle fibres were classified as types I, IIA, IIB or IIC on the basis of the pH lability of their myofibrillar ATPases. There were no differences between the multifidus and the longissimus muscles in the relative occurrence of type I (62 vs. 57%), type IIA (20 vs. 22%) or type IIB fibres (18 vs. 22%), or in the absolute size of fibres (range of mean least diameters 58-66 micron). The oxidative potential (NADH-diaphorase staining intensity) was high in type I and low in type II fibres, irrespective of subgroups, in both muscles. In the females, the type I fibres occupied a relatively larger area (70-75 vs. 54-58% for the males) although the relative number of type I fibres was the same in both sexes. This was due to smaller type II fibres in the females resulting in higher type I/type II area ratios (1.70-1.90 vs. 0.88-0.92 for males). This suggests a difference in functional capacity of lumbar back muscles between males and females. On the other hand, the similarity in histochemical fibre-type distribution between the multifidus and the longissimus muscles does not give support for a functional differentiation between these two anatomically different parts of the lumbar erector spinae in man.

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