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  • 201. Karlsen, Jon
    et al.
    Nilsson, Johnny
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    A new method to record aiming in golf putting  -  applied to elite players2008In: Science and Golf V: proceedings of the World Scientific Congress of Golf / [ed] D. Crews and R. Lutz, Energy in Motion , 2008, p. 395-401Conference paper (Refereed)
  • 202. Karlsen, Jon
    et al.
    Nilsson, Johnny
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Club shaft weight in putting accuracy and perception of swing parameters in golf putting.2007In: Perceptual and Motor Skills, ISSN 0031-5125, E-ISSN 1558-688X, Vol. 105, no 1, p. 29-38Article in journal (Refereed)
    Abstract [en]

    This study assessed how shaft weight influenced golf putting accuracy and subjective perception of swing parameters. Three putters of different shaft weight (100, 420, and 610 gm) were tested by 24 club players. Distance and deviation in direction were measured, and subjective ratings of the putters recorded. Subjects hit the ball further with lighter shafts. The mean distance hit was 100.2, 99.3, and 98.1% of the target distance for the normal, medium, and heavy putter shafts, respectively. Subjectively, the medium heavy putter was rated best on "overall feeling" and it was also rated better than the normal on"feeling of stability in the downswing." The heaviest putter was rated as too heavy by 23 of 24 subjects. There were no significant differences between the putter clubs in distance and directional putting accuracy. The major findings are that the golfers putted 2.1% longer with the 100 gm shaft than with the 610 gm shaft and that the perception of overall feeling of the putter club was not related to performance.

  • 203. Karlsen, Jon
    et al.
    Nilsson, Johnny
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Club shaft weight in putting accuracy and perception of swingparameters in golf putting2007In: Perceptual and Motor Skills, ISSN 0031-5125, E-ISSN 1558-688X, Vol. 105, no 1, p. 29-38Article in journal (Refereed)
    Abstract [en]

    This study assessed how shaft weight influenced golf putting accuracy and subjective perception of swing parameters. Three putters of different shaft weight (100, 420, and 610 gm) were tested by 24 club players. Distance and deviation in direction were measured, and subjective ratings of the putters recorded. Subjects hit the ball further with lighter shafts. The mean distance hit was 100.2, 99.3, and 98.1% of the target distance for the normal, medium, and heavy putter shafts, respectively. Subjectively, the medium heavy putter was rated best on "overall feeling" and it was also rated better than the normal on"feeling of stability in the downswing." The heaviest putter was rated as too heavy by 23 of 24 subjects. There were no significant differences between the putter clubs in distance and directional putting accuracy. The major findings are that the golfers putted 2.1% longer with the 100 gm shaft than with the 610 gm shaft and that the perception of overall feeling of the putter club was not related to performance.

  • 204. Karlsen, Jon
    et al.
    Nilsson, Johnny
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Distance variability in golf putting among highly skilled players: the role of green reading2008In: Annual Review of Golf Coaching, Multi-Science Publishing, 2008Chapter in book (Refereed)
  • 205. Karlsen, Jon
    et al.
    Nilsson, Johnny
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Golf players prefer mallet putters for aiming, but aim more consistent with blade putters2008In: Science and Golf V: proceedings of the World Scientific Congress of Golf Science and Golf V / [ed] D. Crews and R. Lutz, Energy in Motion , 2008, p. 402-407Conference paper (Refereed)
  • 206. Karlsen, Jon
    et al.
    Smith, Gerald
    Nilsson, Johnny
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    The stroke has a minor influence on direction consistencyin golf putting among elite players2008In: Journal of Sports Sciences, ISSN 0264-0414, E-ISSN 1466-447X, Vol. 3, p. 243-250Article in journal (Refereed)
    Abstract [en]

    In the golf instructional literature, the putting stroke is typically given higher priority than green reading and aiming. The main purpose of this study was to assess the importance of the putting stroke for direction consistency in golf putting. Kinematic stroke parameters were recorded from 71 elite golf players (mean handicap = 1.8, s = 4.2) on 1301 putts from about 4 m. Of the different factors deciding stroke direction consistency, face angle was found to be the most important (80%), followed by putter path (17%) and impact point (3%). This suggests that improvements in consistency of putter path and impact point will have very little effect on overall putting direction consistency and should not be prioritized in the training of elite players. In addition, mean stroke direction variability for an elite player (European Tour) was found to be 0.39°, which is good enough to hole about 95% of all 4-m putts. In practice, however, top professionals in tournaments only hole about 17% of 4-m putts. We conclude that the putting stroke of elite golfers has a relatively minor influence on direction consistency.

  • 207. Karlsen, Jon
    et al.
    Smith, Gerald
    Nilsson, Johnny
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    The stroke has only a minor influence on direction consistency in golf putting among elite players.2008In: Journal of Sports Sciences, ISSN 0264-0414, E-ISSN 1466-447X, Vol. 26, no 3, p. 243-50Article in journal (Refereed)
    Abstract [en]

    In the golf instructional literature, the putting stroke is typically given higher priority than green reading and aiming. The main purpose of this study was to assess the importance of the putting stroke for direction consistency in golf putting. Kinematic stroke parameters were recorded from 71 elite golf players (mean handicap = 1.8, s = 4.2) on 1301 putts from about 4 m. Of the different factors deciding stroke direction consistency, face angle was found to be the most important (80%), followed by putter path (17%) and impact point (3%). This suggests that improvements in consistency of putter path and impact point will have very little effect on overall putting direction consistency and should not be prioritized in the training of elite players. In addition, mean stroke direction variability for an elite player (European Tour) was found to be 0.39 degrees, which is good enough to hole about 95% of all 4-m putts. In practice, however, top professionals in tournaments only hole about 17% of 4-m putts. We conclude that the putting stroke of elite golfers has a relatively minor influence on direction consistency.

  • 208. Karlsson, Håkan K R
    et al.
    Nilsson, Per-Anders
    Nilsson, Johnny
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Chibalin, Alexander V
    Zierath, Juleen R
    Blomstrand, Eva
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Eva Blomstrand's research group.
    Branched-chain amino acids increase p70S6k phosphorylation in human skeletal muscle after resistance exercise.2004In: American Journal of Physiology. Endocrinology and Metabolism, ISSN 0193-1849, E-ISSN 1522-1555, Vol. 287, no 1, p. E1-7Article in journal (Refereed)
    Abstract [en]

    The aim of the study was to investigate the effect of resistance exercise alone or in combination with oral intake of branched-chain amino acids (BCAA) on phosphorylation of the 70-kDa S6 protein kinase (p70(S6k)) and mitogen-activated protein kinase (MAPK), extracellular signal-regulated kinase (ERK1/2), and p38 MAPK in skeletal muscle. Seven male subjects performed one session of quadriceps muscle resistance training (4 x 10 repetitions at 80% of one repetition maximum) on two occasions. In a randomized order, double-blind, crossover test, subjects ingested a solution of BCAA or placebo during and after exercise. Ingestion of BCAA increased plasma concentrations of isoleucine, leucine, and valine during exercise and throughout recovery after exercise (2 h postexercise), whereas no change was noted after the placebo trial. Resistance exercise led to a robust increase in p70(S6k) phosphorylation at Ser(424) and/or Thr(421), which persisted 1 and 2 h after exercise. BCAA ingestion further enhanced p70(S6k) phosphorylation 3.5-fold during recovery. p70(S6k) phosphorylation at Thr(389) was unaltered directly after resistance exercise. However, during recovery, Thr(389) phosphorylation was profoundly increased, but only during the BCAA trial. Furthermore, phosphorylation of the ribosomal protein S6 was also increased in the recovery period only during the BCAA trial. Exercise led to a marked increase in ERK1/2 and p38 MAPK phosphorylation, which was completely suppressed upon recovery and unaltered by BCAA. In conclusion, BCAA, ingested during and after resistance exercise, mediate signal transduction through p70(S6k) in skeletal muscle.

  • 209. 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.

  • 210. Kim, Chang
    et al.
    Takala, Timo
    Seger, Jan
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Karpakka, Jarmo
    Training effects of electrically induced dynamic contractions in human quadriceps muscle.1995In: Aviation, Space and Environmental Medicine, ISSN 0095-6562, E-ISSN 1943-4448, Vol. 66, p. 251-255Article in journal (Refereed)
    Abstract [en]

    The effects of electrically induced dynamic muscle contractions on muscle endurance, strength, morphology and enzymatic adaptation were studied in seven male physical education students. The training program consisted of electrically induced one-leg extensions on a modified Krogh cycle with a 30-Watt (W) load for 60 min, 3 times a week for 4 weeks. Muscle fiber type composition was unchanged, but diffusional capacity was increased after electromyostimulation training. The endurance capacity in the trained leg increased by 82% (p < 0.01), but there were no significant changes in citrate synthase, phosphofructokinase activities, and carbonic anhydrase III and myoglobin contents, suggesting that neural adaptation and learning were more important factors for the increased endurance capacity than enzymatic adaptation. Prolyl 4-hydroxylase activity, a marker of collagen biosynthesis, increased 3-fold (p < 0.01) as a result of the training. This could be due to muscle damage caused by electrically induced muscle contractions. In conclusion, electrically induced dynamic muscle contractions can increase muscle endurance without clear concominant changes in muscle morphologic and enzymatic adaptation. Increased prolyl 4-hydroxylase activity could suggest muscle damage caused by electrically induced muscle contractions.

  • 211. 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.

  • 212. Kullberg, Kerstin
    et al.
    Björklund, Anita
    Sidenvall, Birgitta
    Åberg, Anna Cristina
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    'I start my day by thinking about what we're going to have for dinner'- a qualitative study on approaches to food-related activities among elderly men with somatic diseases.2011In: Scandinavian Journal of Caring Sciences, ISSN 0283-9318, E-ISSN 1471-6712, Vol. 25, no 2, p. 227-234Article in journal (Refereed)
    Abstract [en]

    'I start my day by thinking about what we're going to have for dinner'- a qualitative study on approaches to food-related activities among elderly men with somatic diseases The aim of this study was to address the question of how older men with somatic diseases living in their own home approach the question of food-related activities (FRA). Further, any adaptations of these activities necessitated by effects of diseases and of altered life circumstances were explored. Interviews were conducted with a purposeful sample of 18 co-living and single-living men, 64-84 years old. They were diagnosed with Parkinson's disease, rheumatoid arthritis or stroke. In the analysis, a thematic framework was used. The findings revealed three food-related approaches, namely 'Cooking as a pleasure', describing joy in cooking; 'Cooking as a need', indicating no habits or skills in cooking; and 'Food is served', that is, being served meals by a partner. It was found that gender-related roles in particular, but also changed life circumstances, activity limitations, personal interests, and a wish to maintain continuity and independence, affected the men's approaches to these activities. This knowledge may be useful in attempts to facilitate and support FRA among elderly men with diseases. Health care efforts to promote FRA should preferably be individualised in respect to older men's approaches to these activities.

  • 213.
    Körting, Clara
    et al.
    Royal Institute of Technology, Stockholm, Sweden.
    Schlippe, Marius
    Royal Institute of Technology, Stockholm, Sweden.
    Petersson, Sven
    Karolinska Institutet, Stockholm, Sweden..
    Pennati, Gaia Valentina
    Karolinska Institutet, Stockholm, Sweden..
    Tarassova, Olga
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Arndt, Anton
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control. Karolinska Institutet, Stockholm, Sweden..
    Finni, Taija
    University of Jyväskylä, Jyväskylä, Finland.
    Zhao, Kangqiao
    Royal Institute of Technology, Stockholm, Sweden.
    Wang, Ruoli
    Royal Institute of Technology, Stockholm, Sweden.
    In vivo muscle morphology comparison in post-stroke survivors using ultrasonography and diffusion tensor imaging.2019In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 9, no 1, article id 11836Article in journal (Refereed)
    Abstract [en]

    Skeletal muscle architecture significantly influences the performance capacity of a muscle. A DTI-based method has been recently considered as a new reference standard to validate measurement of muscle structure in vivo. This study sought to quantify muscle architecture parameters such as fascicle length (FL), pennation angle (PA) and muscle thickness (tm) in post-stroke patients using diffusion tensor imaging (DTI) and to quantitatively compare the differences with 2D ultrasonography (US) and DTI. Muscle fascicles were reconstructed to examine the anatomy of the medial gastrocnemius, posterior soleus and tibialis anterior in seven stroke survivors using US- and DTI-based techniques, respectively. By aligning the US and DTI coordinate system, DTI reconstructed muscle fascicles at the same scanning plane of the US data can be identified. The architecture parameters estimated based on two imaging modalities were further compared. Significant differences were observed for PA and tm between two methods. Although mean FL was not significantly different, there were considerable intra-individual differences in FL and PA. On the individual level, parameters measured by US agreed poorly with those from DTI in both deep and superficial muscles. The significant differences in muscle parameters we observed suggested that the DTI-based method seems to be a better method to quantify muscle architecture parameters which can provide important information for treatment planning and to personalize a computational muscle model.

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  • 214. Lanferdini, Fábio J
    et al.
    Bini, Rodrigo R
    Figueiredo, Pedro
    Diefenthaeler, Fernando
    Mota, Carlos B
    Arndt, Anton
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Vaz, Marco A
    Differences in Pedaling Technique in Cycling: A Cluster Analysis.2016In: International Journal of Sports Physiology and Performance, ISSN 1555-0265, E-ISSN 1555-0273, Vol. 11, no 7, p. 959-964Article in journal (Refereed)
    Abstract [en]

    PURPOSE: To employ cluster analysis to assess if cyclists would opt for different strategies in terms of neuromuscular patterns when pedaling at the power output of their second ventilatory threshold (POVT2) compared with cycling at their maximal power output (POMAX).

    METHODS: Twenty athletes performed an incremental cycling test to determine their power output (POMAX and POVT2; first session), and pedal forces, muscle activation, muscle-tendon unit length, and vastus lateralis architecture (fascicle length, pennation angle, and muscle thickness) were recorded (second session) in POMAX and POVT2. Athletes were assigned to 2 clusters based on the behavior of outcome variables at POVT2 and POMAX using cluster analysis.

    RESULTS: Clusters 1 (n = 14) and 2 (n = 6) showed similar power output and oxygen uptake. Cluster 1 presented larger increases in pedal force and knee power than cluster 2, without differences for the index of effectiveness. Cluster 1 presented less variation in knee angle, muscle-tendon unit length, pennation angle, and tendon length than cluster 2. However, clusters 1 and 2 showed similar muscle thickness, fascicle length, and muscle activation. When cycling at POVT2 vs POMAX, cyclists could opt for keeping a constant knee power and pedal-force production, associated with an increase in tendon excursion and a constant fascicle length.

    CONCLUSIONS: Increases in power output lead to greater variations in knee angle, muscle-tendon unit length, tendon length, and pennation angle of vastus lateralis for a similar knee-extensor activation and smaller pedal-force changes in cyclists from cluster 2 than in cluster 1.

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  • 215.
    Larsson, Kristina
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences. Sophiahemmet University.
    Ekblom, Örjan
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Åstrand Laboratory of Work Physiology.
    Kallings, Lena
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Åstrand Laboratory of Work Physiology.
    Ekblom, Maria
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control. Karolinska institutet.
    Blom, Victoria
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Sport Psychology research group. Karolinska institutet.
    Job Demand-Control-Support Model as Related to Objectively Measured Physical Activity and Sedentary Time in Working Women and Men.2019In: International Journal of Environmental Research and Public Health, ISSN 1661-7827, E-ISSN 1660-4601, Vol. 16, no 18, article id E3370Article in journal (Refereed)
    Abstract [en]

    A physically active lifestyle incurs health benefits and physically active individuals show reduced reactivity to psychosocial stressors. However, the findings are inconclusive and are based on self-reported physical activity and sedentary time. The present study aimed at studying the associations between psychological stressors (job demand, control, support, JD-C-S) and objectively measured physical activity (PA) on various intensities from sedentary (SED) to vigorous physical activity. The participants were 314 employees from a cross-sectional study. PA data were collected with the accelerometer ActiGraph GT3X (Pensacola, FL, USA), SED data with the inclinometer activPAL (PAL Technologies Ltd., Glasgow, Scotland, UK), and psychosocial stressors with a web questionnaire. Results showed that vigorous-intensity PA was negatively associated with demand (β -0.15, p < 0.05), even when adjusted for the covariates. SED was negatively associated to support (β -0.13, p < 0.05). Stress significantly moderated relations between support and sedentary time (β -0.12, p < 0.05). Moderate PA (MVPA) was negatively associated with demand, but only when controlling for overtime (β -0.13, p < 0.05). MVPA was also negatively associated with control (β -0.15, p < 0.05) but not when work engagement was included in the model. Being more physically active and spending less time sedentary may help to handle job situations with high demand and low support.

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  • 216.
    Larsson, Kristina
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences.
    Ekblom, Örjan
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Åstrand Laboratory of Work Physiology.
    Kallings, Lena
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Åstrand Laboratory of Work Physiology.
    Ekblom, Maria
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Blom, Victoria
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Sport Psychology research group.
    Job demands control model as related to objectively measured physical activity and sitting time in working women and men2019Conference paper (Other academic)
  • 217.
    Larsson, Kristina
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences.
    Kallings, Lena
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Åstrand Laboratory of Work Physiology.
    Ekblom, Örjan
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Åstrand Laboratory of Work Physiology.
    Blom, Victoria
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Sport Psychology research group.
    Andersson, Eva
    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.
    Criterion validity and test-retest reliability of SED-GIH, a single item question for assessment of daily sitting time.2019In: BMC Public Health, ISSN 1471-2458, E-ISSN 1471-2458, Vol. 19, no 1, article id 19:17Article in journal (Refereed)
    Abstract [en]

    BACKGROUND: Sedentary behaviour has been closely linked to metabolic and cardiovascular health and is therefore of importance in disease prevention. A user-friendly tool for assessment of sitting time is thus needed. Previous studies concluded that the present tools used to assess a number of sedentary behaviours are more likely to overestimate sitting than single-item questions which often underestimate sitting time, and that categorical answering options are recommended. In line with this, the single-item question with categorical answering options, SED-GIH, was developed. The aim of this study was to investigate the criterion validity of the SED-GIH question using activPAL3 micro as the criterion measure. The second aim was to evaluate the test-retest reliability of the SED-GIH questionnaire.

    METHOD: In the validity section of this study, 284 middle-aged adults answered a web questionnaire, which included SED-GIH, wore activPAL and filled in a diary log for one week. Spearman's rho assessed the relationship between the SED-GIH answers and the daily average sitting time as monitored by the activPAL (activPAL-SIT), a Weighted Kappa assessed the agreement, ANOVA assessed differences in activPAL-SIT between the SED-GIH answer categories, and a Chi2 compared the proportions of hazardous sitters between the different SED-GIH answer categories. In the reliability section, 95 elderly participants answered the SED-GIH question twice, with a mean interval of 5.2 days. The reliability was assessed with ICC and a weighted Kappa.

    RESULTS: The SED-GIH question correlated moderately with activPAL-SIT (rho = 0.31), with a poor agreement (weighted Kappa 0.12). In total, 40.8% underestimated and 22.2% overestimated their sitting time. The ANOVA showed significant differences in activPAL-SIT between the different SED-GIH answer categories (p < 0.001). The Chi2 showed a significant difference in proportion of individuals sitting more than 10 h per day within each SED-GIH answer category. ICC for the test-retest reliability of SED-GIH was excellent with ICC = 0.86, and the weighted Kappa showed an agreement of 0.77.

    CONCLUSIONS: The unanchored single item SED-GIH question showed excellent reliability but poor validity in the investigated populations. Validity and reliability of SED-GIH is in line with other questionnaires that are commonly used when assessing sitting time.

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  • 218. Laughton, Carrie A
    et al.
    Slavin, Mary
    Katdare, Kunal
    Nolan, Lee
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Bean, Jonathan F
    Kerrigan, D Casey
    Phillips, Edward
    Lipsitz, Lewis A
    Collins, James J
    Aging, muscle activity, and balance control: physiologic changes associated with balance impairment.2003In: Gait & Posture, ISSN 0966-6362, E-ISSN 1879-2219, Vol. 18, no 2, p. 101-8Article in journal (Refereed)
    Abstract [en]

    Older adults demonstrate increased amounts of postural sway, which may ultimately lead to falls. The mechanisms contributing to age-related increases in postural sway and falls in the elderly remain unclear. In an effort to understand age-related changes in posture control, we assessed foot center-of-pressure (COP) displacements and electromyographic data from the tibialis anterior, soleus, vastus lateralis, and biceps femoris collected simultaneously during quiet-standing trials from elderly fallers, elderly non-fallers, and healthy young subjects. Both traditional measures of COP displacements and stabilogram-diffusion analysis were used to characterize the postural sway of each group. Regression analyses were used to assess the relationship between the COP measures and muscle activity. Elderly fallers demonstrated significantly greater amounts of sway in the anteroposterior (AP) direction and greater muscle activity during quiet standing compared with the young subjects, while elderly non-fallers demonstrated significantly greater muscle activation and co-activation compared with the young subjects. No significant differences were found between elderly fallers and elderly non-fallers in measures of postural sway or muscle activity. However, greater postural sway in both the AP and mediolateral (ML) directions and trends of greater muscle activity were found in those older adults who demonstrated lower scores on clinical measures of balance. In addition, short-term postural sway was found to be significantly correlated with muscle activity in each of these groups. This work suggests that high levels of muscle activity are a characteristic of age-related declines in postural stability and that such activity is correlated with short-term postural sway. It is unclear whether increases in muscle activity preclude greater postural instability or if increased muscle activity is a compensatory response to increases in postural sway.

  • 219. Leavy, Breiffni
    et al.
    Åberg, Anna Cristina
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    "Not ready to throw in the towel": perceptions of physical activity held by older adults in Stockholm and Dublin.2010In: Journal of Aging and Physical Activity, ISSN 1063-8652, E-ISSN 1543-267X, Vol. 18, no 2, p. 219-36Article in journal (Refereed)
    Abstract [en]

    The aim of this qualitative study was to explore and describe the perceptions of physical activity held by older urban Swedish and Irish adults. Qualitative interviews were carried out with 30 people age 65 years and older (mean age 74.5), of whom 15 were living in Dublin and 15 were living in Stockholm. The "thematic framework" approach was used to analyze the data. Three central themes were identified regarding people's perceptions of physical activity: physical activity as self-expression, physical activity as interaction, and physical activity as health promotion. Participants' perceptions of physical activity tended to relate to their perceived level of physical activity, regardless of their cultural background. Certain culture-specific motivators and barriers to exercise were also identified. Less active Irish men were more likely to underestimate the health-promoting benefits of exercise.

  • 220.
    Liljedahl, Johanna B
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Bjerkefors, Anna
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Arndt, Anton
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control. Karolinska institutet.
    Nooijen, Carla F J
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences. Karolinska institutet.
    Para-cycling race performance in different sport classes.2020In: Disability and Rehabilitation, ISSN 0963-8288, E-ISSN 1464-5165, p. 1-5Article in journal (Refereed)
    Abstract [en]

    Purpose: The para-cycling classification system, consisting of five classes (C1-C5) for bicycling (C5 athletes having least impairments), is mostly based on expert-opinion rather than scientific evidence. The aim of this study was to determine the differences in race performance between para-cycling classes. Methods: From official results of the men's 1 km time trials for classes C1-C5 of seven Union Cycliste Internationale World Championships and Paralympics, median race speed of the five fastest athletes in each class was calculated (n = 175). Para-cycling results were expressed as a percentage of able-bodied performance using race results from the same years (n = 35). To assess differences between consecutive classes, Kruskal-Wallis tests with Mann-Whitney U post hoc tests were performed, correcting for multiple testing (p < 0.013). Results: Para-cyclists in C1 reached 75% (median ± interquartile range = 44.8 ± 4.2 km/h) and in C5 90% (53.5 ± 2.9 km/h) of able-bodied race speed (59.4 ± 0.9 km/h). Median race speed between consecutive classes was significantly different (χ2 = 142.6, p < 0.01), except for C4 (52.1 ± 2.8 km/h) and C5 (U = 447.0, p = 0.05). Conclusion: Current para-cycling classification does not clearly differentiate between classes with least impairments.IMPLICATIONS FOR REHABILITATIONThe current classification system is not evidence-based and does not clearly differentiate between relevant groups of para-cyclists.An evidence-based para-cycling classification system is essential for a fair and equitable competition.Fair competition will make it more interesting and increase participation.Para-cycling can inspire everyone with and even those without disabilities to be physically active.

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  • 221.
    Lindberg, Thomas
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Arndt, Anton
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Norrbrink, Cecilia
    Department of Clinical Sciences, Karolinska Institutet Danderyd Hospital, Stockholm, Sweden.
    Wahman, Kerstin
    Department of Neurobiology, Care Sciences and Society (NVS), Division of Neurorehabilitation, Karolinska Institutet.
    Bjerkefors, Anna
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Effects of seated double-poling ergometer training on aerobic and mechanical power in individuals with spinal cord injury2012In: Journal of Rehabilitation Medicine, ISSN 1650-1977, E-ISSN 1651-2081, Vol. 44, no 10, p. 893-898Article in journal (Refereed)
    Abstract [en]

    OBJECTIVE: To determine whether regular interval training on a seated double-poling ergometer can increase physical capacity and safely improve performance towards maximal level in individuals with spinal cord injury.

    METHODS: A total of 13 subjects with spinal cord injury (injury levels T5-L1) performed 30 sessions of seated double-poling ergometer training over a period of 10 weeks. Sub-maximal and maximal double-poling ergometer tests were performed before (test-retest) and after this training period. Oxygen uptake was measured using the Douglas Bag system. Three-dimensional kinematics were recorded using an optoelectronic system and piezoelectric force sensors were used to register force in both poles.

    RESULTS: The mean intra-class correlation coefficient for test-retest values was 0.83 (standard deviation 0.11). After training significant improvements were observed in people with spinal cord injury in oxygen uptake (22.7%), ventilation (20.7%) and blood lactate level (22.0%) during maximal exertion exercises. Mean power per stroke and peak pole force increased by 15.4% and 23.7%, respectively. At sub-maximal level, significantly lower values were observed in ventilation (-12.8%) and blood lactate level (-25.0%).

    CONCLUSION: Regular interval training on the seated double-poling ergometer was effective for individuals with spinal cord injury below T5 level in terms of improving aerobic capacity and upper-body power output. The training was safe and did not cause any overload symptoms.

  • 222. Liu, Anmin
    et al.
    Nester, Christopher
    Jones, Richard
    Lundgren, Paul
    Lundberg, Arne
    Arndt, Anton
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Wolf, Peter
    The Effect of an Antipronation Foot Orthosis on Ankle and Subtalar Kinematics2012In: Medicine & Science in Sports & Exercise, ISSN 0195-9131, E-ISSN 1530-0315, Vol. 44, no 12, p. 2384-91Article in journal (Refereed)
    Abstract [en]

    INTRODUCTION/PURPOSE:

    The aim of this study was to describe the effect of an anti pronation foot orthosis on motion of the heel relative to the leg and explore the individual contributions of the ankle and subtalar joints to this effect.

    METHODS:

    Five subjects were investigated using invasive intracortical pins to track the movement of the tibia, talus and calcaneus during walking with and without a foot orthosis.

    RESULTS:

    The anti pronation foot orthosis produced small and unsystematic reductions in eversion and abduction of the heel relative to the leg at various times during stance. Changes in calcaneus-tibia motion were comparable to those described in the literature (1-3°). Changes at both the ankle and subtalar joints contributed to this orthotic effect. However, the nature and scale of changes was highly variable between subjects. Peak angular position, range of motion and angular velocity in frontal and transverse planes were affected to different degrees in different subjects. In some cases changes occurred mainly at the ankle, in other cases changes occurred mainly at the subtalar joint.

    CONCLUSION:

    The changes in ankle and subtalar kinematics in response to the foot orthosis contradict existing orthotic paradigms that assume that changes occur only at the subtalar joint. The kinematic changes due to the orthosis are indicative of a strong interaction between the often common function of the ankle and subtalar joints.

  • 223.
    Lundberg, Arne
    et al.
    Department of Orthopaedics, CLINTEC, Karolinska Institute, Stockholm, Sweden.
    Aguilera, Ana
    Centre of Analysis, Treatment and Data Modelling, Faculty of Science and Technology,.
    Cappozzo, Aurelio
    Department of Human Movement and.
    Arndt, Anton
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Begon, Mickael
    Department of Kinesiology, University of Montreal, Canada.
    Entropy in the List of Authors of Scientific Papers2014In: Annals of improbable research, Vol. 20, no 1, p. 15-17Article in journal (Other (popular science, discussion, etc.))
    Abstract [en]

    Conclusion

    It is the firm belief of the present authors that there should not be more than three names on an author list, and rather than appear on a longer list of authors, one should withdraw willingly. Furthermore, the remaining authors should determine an order such that the respective work of each contributor is known, whatever it is. If not, then the lack of input from the mysterious authors should be officially recognized by all journals real, imaginary, or improbable. We hope that this paper will serve as a guideline to future authors and mysterious contributors as well.

  • 224. Löscher, W N
    et al.
    Cresswell, A G
    Thorstensson, Alf
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Recurrent inhibition of soleus alpha-motoneurons during a sustained submaximal plantar flexion.1996In: Electroencephalography and Clinical Neurophysiology, ISSN 0013-4694, E-ISSN 0013-4649, Vol. 101, no 4, p. 334-8Article in journal (Refereed)
    Abstract [en]

    During 10 min of sustained isometric plantar flexion at 20% of maximal voluntary contraction, recurrent inhibition of soleus alpha-motoneurons was studied in 9 healthy subjects (age 22-37 years). Recurrent inhibition was brought about by a conditioning H-reflex and assessed by a test H-reflex delivered 10 ms later. The amplitude of the test H-reflex during the tenth minute of the contraction (16.9 +/- 13.2% of the maximal compound motor action potential) was significantly increased as compared to that during the first minute (9.8 +/- 7.6%), while the conditioning H-reflex remained unchanged. Concomitantly, muscle fatigue was evidenced by a significant increase in amplitude of the soleus electromyogram. The increase of the test-H-reflex amplitude implies that a decrease in recurrent inhibition occurred during the sustained submaximal contraction, which contrasts results from studies on maximal voluntary contractions. These results indicate a modulation of soleus Renshaw interneurons, which is likely to serve the purpose of optimising motor unit recruitment and firing rates of this muscle during a sustained submaximal contraction.

  • 225. 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.

  • 226. 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.
    Central fatigue during a long-lasting submaximal contraction of the triceps surae.1996In: Experimental Brain Research, ISSN 0014-4819, E-ISSN 1432-1106, Vol. 108, no 2, p. 305-14Article in journal (Refereed)
    Abstract [en]

    Our purpose was to study central fatigue and its dependence on peripheral reflex inhibition during a sustained submaximal contraction of the triceps surae. In 11 healthy subjects, superimposed twitches, surface electromyograms (EMG) from the medial head of the gastrocnemius (MG) and soleus (SOL) muscles, maximal compound motor action potentials (M(max)), tracking error and tremor were recorded during sustained fatiguing contractions at a torque level corresponding to 30% of maximal voluntary contraction (MVC). When the endurance limit (401 +/- 91 s) of the voluntary contraction (VC-I) was reached, the triceps surae could be electrically stimulated to the same torque level for an additional 1 min in 10 of the 11 subjects. These subjects were then able to continue the contraction voluntarily (voluntary contraction II, VC-II) for another 85 +/- 48 s. At the endurance limit of VC-I, the superimposed twitch was larger than during the unfatigued MVC, while there was no significant difference between the twitch at the endurance limit of VC-II and MVC. The EMG amplitude of both MG and SOL at the endurance limit of VC-I was significantly less than that during the MVC. While the EMG amplitude of MG increased further during VC-II, SOL EMG remained unchanged, neither muscle reaching their unfatigued MVC values. This difference was diminished for SOL by taking into account its decrease in M(max) found during VC-II, and relative EMG levels approached their MVC values. These results clearly indicate that a higher voluntary muscle activation was achievable after 1 min of electrical muscle stimulation, which continued metabolic stress and contractile fatigue processes but allowed for supraspinal, muscle spindle and/or motoneuronal recovery. It is concluded that peripheral reflex inhibition of alpha-motoneurons via small-diameter muscle afferents is of minor significance for the development of the central fatigue that was found to occur during the first voluntary contraction.

  • 227. 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.
    Excitatory drive to the alpha-motoneuron pool during a fatiguing submaximal contraction in man.1996In: Journal of Physiology, ISSN 0022-3751, E-ISSN 1469-7793, Vol. 491 ( Pt 1), p. 271-80Article in journal (Refereed)
    Abstract [en]

    1. This study was undertaken to examine changes of excitatory drive to the triceps surae alpha-motoneuron pool during fatiguing submaximal isometric contractions in man. Eight healthy subjects maintained isometric plantar flexions at 30 percent of maximum voluntary contraction (MVC) until the limit of endurance (range, 6-9 min). 2. Excitability of the alpha-motoneuron pool to Ia afferent stimulation (H reflex), electromyograms (EMG) and maximum compound motor unit action potentials (Mmax) from the lateral (LG) and medial heads (MG) of the gastrocnemius as well as from the soleus muscle (Sol) were recorded throughout the contraction. Superimposed maximum twitch torques (twitch occlusion) and isometric torque fluctuations (tremor) were also recorded as indirect measures of excitatory drive. 3. H reflexes were studied at different levels of underlying voluntary contraction to assess the relationship between H reflex amplitude and excitatory drive. With increasing levels of underlying contraction up to MVC, superimposed H reflex amplitude increased for LG in six subjects, for MG in all eight and for Sol in five. In the remaining cases, H reflex amplitude first increased and then plateaued between 30-50% of MVC. 4. H/Mmax ratios increased during fatigue in those muscles that showed an H reflex amplitude increase with high levels of underlying contraction. In these cases, LG and MG H/Mmax increased significantly after about 50 and 20% of endurance time onward, respectively, whereas Sol H/Mmax demonstrated a significant increase up to 40% of endurance time. 5. EMG root mean square (r.m.s.) increased linearly throughout the contraction for all three muscles, while tremor r.m.s. increased in a non-linear way, with a steeper increase from 60% of endurance time onward. Superimposed twitch amplitude decreased significantly from 25% of endurance time onward. 6. It is concluded that during fatiguing isometric contractions at 30% of MVC, the excitatory drive to the triceps surae alpha-motoneuron pool increases. This is thought to be a compensatory mechanism to facilitate recruitment of new, unfatigued motor units (MUs), and/or to increase MU firing rates. The facts that the twitch is not abolished at endurance limit and that the EMG does not attain its unfatigued MVC level are strong indications that central fatigue occurred during the sustained submaximal contraction.

  • 228. Löscher, Wolfgang N
    et al.
    Nordlund (Ekblom), Maria M
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Central fatigue and motor cortical excitability during repeated shortening and lengthening actions.2002In: Muscle and Nerve, ISSN 0148-639X, E-ISSN 1097-4598, Vol. 25, no 6, p. 864-72Article in journal (Refereed)
    Abstract [en]

    A decline in voluntary muscle activation and adaptations in motor cortical excitability contribute to the progressive decline in voluntary force during sustained isometric contractions. However, the neuronal control of muscle activation differs between isometric and dynamic contractions. This study was designed to investigate voluntary activation, motor cortex excitability, and intracortical inhibition during fatiguing concentric and eccentric actions. Eight subjects performed 143 torque motor-controlled, repeated shortening and lengthening actions of the elbow flexor muscles. Transcranial magnetic stimulation (TMS) was applied three times every 20 cycles. Magnetic evoked motor potentials (MEP), duration of the silent period (SP), and the torque increase due to TMS were analyzed. TMS resulted in a small torque increase in unfatigued actions. With repeated actions, voluntary torque dropped rapidly and the amplitude of the TMS-induced twitches increased, especially during repeated lengthening actions. MEP area of biceps brachii and brachioradialis muscles increased during repeated actions to a similar extent during lengthening and shortening fatigue. The duration of biceps and brachioradialis SP did not change with fatigue. Thus, voluntary activation became suboptimal during fatiguing dynamic actions and motor cortex excitability increased without any changes in intracortical inhibition. The apparent dissociation of voluntary activation and motor cortex excitability suggests that the central fatigue observed, especially during lengthening actions, did not result from changes in motor cortex excitability.

  • 229. Maiwald, Christian
    et al.
    Arndt, Anton
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Nester, Chris
    Jones, Richard
    Lundberg, Arne
    Wolf, Peter
    The effect of intracortical bone pin application on kinetics and tibiocalcaneal kinematics of walking gait2017In: Gait & Posture, ISSN 0966-6362, E-ISSN 1879-2219, Vol. 52, p. 129-134Article in journal (Refereed)
    Abstract [en]
    • Gait analysis using bone anchored markers requires local anaesthesia, which may affect subjects gait patterns.
    • Kinetic and kinematic variables were collected using two protocols (skin vs. bone anchored markers).
    • No systematic differences were found between the two protocols.
    • We conclude that the validity of the recorded variables is not affected by local anaesthesia.

    Bone anchored markers using intracortical bone pins are one of the few available methods for analyzing skeletal motion during human gait in-vivo without errors induced by soft tissue artifacts. However, bone anchored markers require local anesthesia and may alter the motor control and motor output during gait. The purpose of this study was to examine the effect of local anesthesia and the use of bone anchored markers on typical gait analysis variables. Five subjects were analyzed in two different gait analysis sessions. In the first session, a protocol with skin markers was used. In the second session, bone anchored markers were added after local anesthesia was applied. For both sessions, three dimensional infrared kinematics of the calcaneus and tibia segments, ground reaction forces, and plantar pressure data were collected. 95% confidence intervals and boxplots were used to compare protocols and assess the data distribution and data variability for each subject. Although considerable variation was found between subjects, within-subject comparison of the two protocols revealed non-systematic effects on the target variables. Two of the five subjects walked at reduced gait speed during the bone pin session, which explained the between-session differences found in kinetic and kinematic variables. The remaining three subjects did not systematically alter their gait pattern between the two sessions. Results support the hypothesis that local anesthesia and the presence of bone pins still allow a valid gait pattern to be analyzed.

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  • 230. Martinsen, E
    et al.
    Hovland, A
    Kjellman, B
    Taube, J
    Andersson, Eva
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Om depression2018In: Fysisk aktivitet som medicin: En praktisk handbok utifrån FYSS / [ed] Ing-Marie Dohrn, Stockholm: SISU idrottsböcker , 2018, p. 177-182Chapter in book (Other (popular science, discussion, etc.))
  • 231.
    Martinsen, Egil W
    et al.
    Oslo universitetssjukhus.
    Hovland, Anders
    Universitetet i Bergen.
    Kjellman, Bengt
    Karolinska institutet.
    Taube, Jill
    Landstinget i Värmland.
    Andersson, Eva
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Fysisk aktivitet vid depression2016In: FYSS 2017: fysisk aktivitet i sjukdomsprevention och sjukdomsbehandling, Läkartidningen förlag , 2016, p. 362-370Chapter in book (Other academic)
    Abstract [sv]

    Sammanfattande rekommendation

    Personer med depression bör rekommenderas aerob eller muskelstärkande fysisk aktivitet för att minska depressiva symtom, måttligt starkt vetenskapligt underlag (evidensstyrka +++), och förbättra livskvalitet, begränsat vetenskapligt underlag (evidensstyrka ++).

    Vid lindrig eller måttlig depression reducerar fysisk aktivitet depressiva symtom i liknande grad som antidepressiva läkemedel eller kognitiv beteendeterapi (KBT). Måttligt starkt vetenskapligt underlag (evidensstyrka +++).

    Om enbart muskelstärkande fysisk aktivitet väljs i syfte att behandla depression, bör den kompletteras med aerob fysisk aktivitet för att minska risken för hjärt-kärlsjukdom, eftersom denna risk är förhöjd vid depression.

  • 232.
    Martinsen, Egil W.
    et al.
    Oslo universitetssjukhus.
    Hovland, Anders
    Universitet i Bergen.
    Kjellman, Bengt
    Karolinska insitutet.
    Taube, Jill
    Landstinget i Värmland.
    Andersson, Eva
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control. Karolinska institutet.
    Fysisk aktivitet vid depression: Forskning pågår2017In: Fysioterapi, ISSN 1653-5804, no 5, p. 34-39Article in journal (Other academic)
    Abstract [sv]

    Vi har nöjet att publicera kapitel 2.8 Fysisk aktivitet vid depression ur  Fysisk aktivitet i sjukdomsprevention och sjukdomsbehandling, FYSS 2017  med tillstånd av Yrkesföreningar för Fysisk Aktivitet (YFA). Detta kapitel samt  ytterligare drygt 30 kapitel ur FYSS 2017 kan laddas ner från www.fyss.se.  Samtliga 53 kapitel är samlade i boken FYSS 2017 utgiven av Läkartidningen förlag AB.

    SAMMANFATTANDE REKOMMENDATION •  Personer med depression bör rekommenderas aerob eller muskelstärkande fysisk aktivitet för att minska depressiva symtom. Måttligt starkt vetenskapligt underlag (evidensstyrka +++). •  Fysisk aktivitet reducerar depressiva symtom i liknande grad som antidepressiva läkemedel eller KBT vid lindrig och måttlig depression. Måttligt starkt vetenskapligt underlag (evidensstyrka +++). •  Om enbart muskelstärkande fysisk aktivitet väljs i syfte att behandla depression, bör den kompletteras med aerob fysisk aktivitet för att minska risken för kardiovaskulär sjukdom, eftersom denna risk är förhöjd vid depression.

  • 233.
    Meckbach, Jane
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Forskningsgruppen för pedagogik, idrott och fritidskultur.
    Ekblom, Maria
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Från magisterkurs till masterexamen2014In: Från Kungl. Gymnastiska Centralinstitutet till Gymnastik- och idrottshögskolan: en betraktelse av de senaste 25 åren som del av en 200-årig historia / [ed] Suzanne Lundvall, Stockholm: Gymnastik- och idrottshögskolan, GIH , 2014, p. 127-132Chapter in book (Other (popular science, discussion, etc.))
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  • 234. Michaud, B.
    et al.
    Jackson, M.
    Arndt, Anton
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Lundberg, A.
    Begon, M.
    Determining in vivo sternoclavicular, acromioclavicular and glenohumeral joint centre locations from skin markers, CT-scans and intracortical pins: A comparison study2016In: Medical Engineering and Physics, ISSN 1350-4533, E-ISSN 1873-4030, Vol. 38, no 3, p. 290-296Article in journal (Refereed)
    Abstract [en]
    • CoR were located using anatomical, predictive, functional and imaging-based methods.
    • Gold-standard locations were obtained using intracortical pins.
    • Sternoclavicular joint: our findings are in agreement with ISB (Wu, 2005).
    • Acromioclavicular joint: anatomical method of by van der Helm (1996) is suggested.
    • Glenohumeral joint: the regression equation of Rab (2002) is suggested. 

    To describe shoulder motion the sternoclavicular, acromioclavicular and glenohumeral joint centres must be accurately located. Within the literature various methods to estimate joint centres of rotation location are proposed, with no agreement of the method best suited to the shoulder. The objective of this study was to determine the most reliable non-invasive method for locating joint centre locations of the shoulder complex. Functional methods using pin mounted markers were compared to anatomical methods, functional methods using skin mounted markers, imaging-based methods using CT-scan data, and regression equations. Three participants took part in the study, that involved insertion of intracortical pins into the clavicle, scapula and humerus, a CT-scan of the shoulder, and finally data collection using a motion analysis system. The various methods to estimate joint centre location did not all agree, however suggestions about the most reliable non-invasive methods could be made. For the sternoclavicular joint, the authors suggest the anatomical method using the most ventral landmark on the sternoclavicular joint, as recommended by the International Society of Biomechanics. For the acromioclavicular joint, the authors suggest the anatomical method using the landmark defined as the most dorsal point on the acromioclavicular joint, as proposed by van der Helm. For the glenohumeral joint, the simple regression equation of Rab is recommended.

  • 235. Moritani, T
    et al.
    Oddson, L
    Thorstensson, Alf
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Electromyographic evidence of selective fatigue during the eccentric phase of stretch/shortening cycles in man.1990In: European Journal of Applied Physiology and Occupational Physiology, ISSN 0301-5548, E-ISSN 1432-1025, Vol. 60, no 6, p. 425-9Article in journal (Refereed)
    Abstract [en]

    Ten male subjects were tested to determine the effects of muscle fatigue upon the activation pattern of the two main ankle extensor muscles, the 'slow-twitch' soleus (SOL) and the relatively 'fast-twitch' medial gastrocnemius (MG), during a fatiguing 60-s trial of hopping to maximal height. The myoelectric signals from SOL and MG were recorded together with the vertical ground reaction force signal and analysed by means of a computer-aided electromyograph (EMG) contour analysis, i.e. two-dimensional frequency distributions were obtained relating the activation patterns of the two synergists. The EMGs were also full-wave rectified and integrated (IEMG) according to three phases of the hopping movement (PRE, pre-activation phase; ECC, eccentric phase; CON, concentric phase). Results indicated that there were significant decreases (P less than 0.01) in the peak ground reaction force, the height of hopping and the mechanical power per unit body weight at the end of the fatiguing contractions. These decreases in mechanical parameters were accompanied by significant (P less than 0.01) decreases in all three phases of MG IEMG while SOL IEMG showed no such significant declines, except in the CON phase. Thus, the decreased mechanical parameters could in large part be accounted for by the substantial and selective decline of the excitation level of the relatively fast-twitch MG muscle. Our data suggest that the centrally mediated pre-activation of the fatiguable MG muscle as well as the MG activation during the eccentric phase, which is largely controlled by supraspinal inputs and stretch-reflex modulation, are most affected by fatigue changes during repeated maximal stretch/shortening cycles of the ankle extensors.

  • 236. 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)
  • 237. 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.

  • 238.
    Moritani, Toshio
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Fuchi, Tokio
    Oddsson, Lars
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Andersson, Eva
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Applications of fast fourier transform (FFT) in noninvasive physiological measurements in sport science.1988In: J Sports Med Sci (Japan), Vol. 2, no 1, p. 27-42Article in journal (Refereed)
  • 239.
    Nilsson, Johnny
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Laboratoriet för tillämpad idrottsvetenskap, LTIV2014In: Från Kungl. Gymnastiska Centralinstitutet till Gymnastik- och idrottshögskolan: en betraktelse av de senaste 25 åren som del av en 200-årig historia / [ed] Suzanne Lundvall, Stockholm: Gymnastik- och idrottshögskolan, GIH , 2014, p. 154-160Chapter in book (Other (popular science, discussion, etc.))
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  • 240.
    Nilsson, Johnny
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Sport innovation2014In: Från Kungl. Gymnastiska Centralinstitutet till Gymnastik- och idrottshögskolan: en betraktelse av de senaste 25 åren som del av en 200-årig historia / [ed] Suzanne Lundvall, Stockholm: Gymnastik- och idrottshögskolan, GIH , 2014, p. 263-271Chapter in book (Other (popular science, discussion, etc.))
    Download full text (pdf)
    fulltext
  • 241.
    Nilsson, Johnny
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Csergö, Sandor
    Gullstrand, Lennart
    Tveit, Per
    Refsnes, Per Egil
    Work-time profile, blood lactate concentration and rating of perceived exertion in the 1998 Greco-Roman Wrestling World Championship.2002In: Journal of Sports Sciences, ISSN 0264-0414, E-ISSN 1466-447X, Vol. 20, no 11, p. 939-45Article in journal (Refereed)
    Abstract [en]

    The aim of this study was to examine work-time profiles, blood lactate concentrations and perceived exertion among Greco-Roman wrestlers in the 1998 World Championship. Forty-two senior wrestlers from nine nations were studied in 94 matches. Each match was recorded with a video camera (Panasonic AG 455, film rate: 25 Hz) and analysed for duration of work (wrestling) and rest (interrupt) periods. Blood lactate concentration was determined with an electrochemical device (Analox P-LM5) and a rating of perceived exertion scale (Borg) was used to estimate general exertion and exertion in the extremity and trunk muscles. The mean duration of the matches was 427 s (range 324-535 s), with mean durations of work and rest of 317 and 110 s, respectively. The mean periods of work and rest were 37.2 and 13.8 s, respectively. Mean blood lactate concentration was 14.8 mmol x 1(-1) (range 6.9-20.6). The difference in mean blood lactate concentration between the first- and final-round matches was not significant (P > 0.05). Blood lactate concentration was significantly higher (P < 0.04) in matches of long duration than in those of short duration. The mean general rating of perceived exertion for all matches was 13.8 according to the scale used. Most of the wrestlers (53.3%) perceived exertion to be highest in the flexors of the forearm, followed by the deltoids (17.4%) and the biceps brachii muscles (12.0%). In addition to a relatively high rating of perceived exertion in the arm muscles, this indicates a high specific load on the flexor muscles of the forearm.

  • 242.
    Nilsson, Johnny E
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Holmberg, Hans-Christer
    Tveit, Per
    Hallén, Jostein
    Effects of 20-s and 180-s double poling interval training in cross-country skiers.2004In: European Journal of Applied Physiology, ISSN 1439-6319, E-ISSN 1439-6327, Vol. 92, no 1-2, p. 121-7Article in journal (Refereed)
    Abstract [en]

    The purpose of this study was to investigate the effect of upper body 20-s or 180-s interval training, using a double poling ergometer, on upper body power output and selected physiological and biomechanical parameters in cross-country skiers. Twenty (12 male, 8 female) well-trained cross-country skiers took part. Two intervention groups, a 20-s interval training group (IT20; n=6) and a 180-s interval training group (IT180; n=7), underwent training three times a week for 6 weeks on a double poling ergometer. A third group served as a control (CON; n=7) and followed the same training program as the IT20 and IT180 groups without the double poling ergometer interval training. The IT20 and IT180 groups significantly (P<0.05) increased both peak and mean power in a 30-s test and mean power in a 6-min test after double poling training. There was a significant improvement in work efficiency in both IT20 and IT180 (P<0.05) and, in IT180, a significant reduction (P<0.05) in blood lactate concentration at given sub-maximal workloads. VO(2peak) increased significantly during double poling in IT180 ( P<0.05) only. VO(2max) did not change significantly in either group. There were no significant changes in any of the test variables in CON. In conclusion, this study shows that 6 weeks of 20-s or 180-s double poling interval training, three times a week, significantly increases power output in both 30-s and 6-min tests, as well as in selected physiological and biomechanical parameters in well-trained cross-country skiers.

  • 243.
    Nilsson, Johnny E
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Rosdahl, Hans G
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Contribution of Leg Muscle Forces to Paddle Force and Kayak Speed During Maximal Effort Flat-Water Paddling.2016In: International Journal of Sports Physiology and Performance, ISSN 1555-0265, E-ISSN 1555-0273, Vol. 11, no 1, p. 22-27Article in journal (Refereed)
    Abstract [en]

    The purpose was to investigate the contribution of leg-muscle-generated forces to paddle force and kayak speed during maximal-effort flat-water paddling. Five elite male kayakers at national and international level participated. The participants warmed up at progressively increasing speeds and then performed a maximal-effort, non-restricted, paddling sequence. This was followed after five minutes' rest by a maximal-effort paddling sequence with the leg action restricted i.e. the knee joints "locked". Left- and right-side foot-bar and paddle forces were recorded with specially designed force devices. In addition, knee angular displacement of the right and left knee was recorded with electrogoniometric technique and the kayak speed was calculated from GPS signals sampled at 5Hz. The results showed that reduction in both push and pull foot-bar forces resulted in a reduction of 21% and 16% in mean paddle stroke force and kayak mean speed, respectively. Thus, the contribution of foot-bar force from lower limb action significantly contributes to the kayakers paddling performance.

  • 244.
    Nilsson, Johnny E
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, The Laboratory of Applied Sports Science (LTIV).
    Rosdahl, Hans G
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    New Devices for Measuring Forces on the Kayak Foot-Bar and on the Seat During Flat-Water Kayak Paddling: a technical report.2014In: International Journal of Sports Physiology and Performance, ISSN 1555-0265, E-ISSN 1555-0273, Vol. 9, no 2, p. 365-70Article in journal (Refereed)
    Abstract [en]

    The purpose was to develop and validate portable force-measurement devices for recordings of push and pull forces applied by each foot to the foot-bar of a kayak, and the horizontal force at the seat. A foot-plate on a single-point force transducer mounted on the kayak foot-bar underneath each foot allowed the push and pull forces to be recorded. Two metal frames interconnected with four linear ball-bearings and a force transducer allowed recording of horizontal seat force. The foot-bar force device was calibrated by loading each foot plate with weights in the push pull direction perpendicular to the foot plate surface while the seat force device was calibrated to horizontal forces with and without weights on the seat. A strong linearity (r2=0.99-1.0) was found between transducer output signal and load force in the push and pull directions for both foot-bar transducers perpendicular to the foot plate and the seat-force measuring device. Reliability of both devices was tested by means of a test-retest design. The coefficient of variation (CV) for foot-bar push and pull forces ranged from 0.1 to 1.1% and the CV for the seat forces varied between 0.6 - 2.2%. The present study opens up for new investigations of the forces generated within the kayak and ways to optimize kayak paddling performance.

  • 245.
    Nilsson, Johnny
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Haugen, Per
    Knee angular displacement and extensor muscle activity in telemark skiing and in ski-specific strength exercises.2004In: Journal of Sports Sciences, ISSN 0264-0414, E-ISSN 1466-447X, Vol. 22, no 4, p. 357-64Article in journal (Refereed)
    Abstract [en]

    Much of the training of competitive telemark skiers is performed as dry-land exercises. The specificity of these exercises is important for optimizing the training effect. Our aim here was to study the activation of the knee extensor musculature and knee angular displacement during competitive telemark skiing and during dry-land strength training exercises to determine the specificity of the latter. Specificity was analysed with respect to angular amplitude, angular velocity, muscle action and electromyographic (EMG) activity. Five male telemark skiers of national and international standard volunteered to participate in the study, which consisted of two parts: (1) skiing a telemark ski course and (2) specific dry-land strength training exercises for telemark skiing (telemark jumps and barbell squats). The angular displacement of the right knee joint was recorded with an electrogoniometer. A tape pressure sensor was used to measure pressure between the sole of the foot and the bottom of the right ski boot. Electromyographic activity in the right vastus lateralis was recorded with surface electrodes. The EMG activity recorded during maximum countermovement jumps was used to normalize the EMG activity during telemark skiing, telemark jumps and barbell squats. The results showed that knee angular displacement during telemark skiing and dry-land telemark jumps had four distinct phases: a flexion (F1) and extension (E1) phase during the thrust phase of the outside ski/leg in the turn/jump and a flexion (F2) and extension (E2) phase when the leg was on the inside of the turn/jump. The vastus lateralis muscle was activated during F1 and E1 in the thrust phase during telemark skiing and telemark jumps. The overall net knee angular amplitude was significantly greater (P < 0.05) for telemark jumps than for telemark skiing. Barbell squats showed a knee angular amplitude significantly greater than that in telemark skiing (P < 0.05). The mean knee angular velocity of the F1 and E1 phases during telemark skiing was about 0.47 rad x s(-1); during barbell squats, it was about 1.22 rad x s(-1). The angular velocity during telemark jumps was 2.34 and 1.59 rad x s(-1) in the F1 and E1 phase, respectively. The normalized activation level of the EMG bursts during telemark skiing, telemark jumps and barbell squats was 70-80%. In conclusion, the muscle action and level of activation in the vastus lateralis during the F1 and E1 phases were similar during telemark skiing and dry-land exercises. However, the dry-land exercises showed a larger knee extension and flexion amplitude and angular velocity compared with telemark skiing. It appears that an adjustment of knee angular velocity during barbell squats and an adjustment of knee angle amplitude during both telemark jumps and barbell squats will improve specificity during training.

  • 246.
    Nilsson, Johnny
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Jakobsen, Vidar
    Tveit, Per
    Eikrehagen, Olav
    Pole length and ground reaction forces during maximal double poling in skiing.2003In: Sports biomechanics / International Society of Biomechanics in Sports, ISSN 1476-3141, Vol. 2, no 2, p. 227-36Article in journal (Refereed)
    Abstract [en]

    The purpose of the investigation was to study the relationship between thrust phase duration, ground reaction force, velocity increase after pole thrust and pole angles versus pole length during double poling in roller skiing. Seven male regional elite cross-country skiers volunteered as subjects for the study. The subjects performed a maximal double pole thrust on roller skis with each of the three different pole lengths: 'short', self-selected (normal) and 'long'. The short and long poles were 7.5 cm shorter and 7.5 cm longer than the self-selected pole length. The subjects made seven maximal pole thrusts with each pole length, which were randomly selected during 21 trials. For each trial the subjects accelerated from a 1.2 m high downhill slope attaining a speed of 3.92 m.s-1 before making a maximal double pole thrust on a force plate placed at the bottom of the slope. The vertical (F2), anterior-posterior (Fy) and mediolateral (Fx) reaction forces of the left pole were measured by the force plate. The positions of the pole were recorded in 3-D by an opto-electronic system. Thrust phase duration, impulse, mean force, velocity increase after pole thrust and pole angles were calculated from the recorded data. Double poling with long poles produced a significantly larger propulsive anterior-posterior reaction force impulse and velocity increase than normal (p < .05) and short poles (p < .05). This was in spite of a larger mean anterior-posterior reaction force being produced with short poles. Thus, thrust phase duration was a primary factor in determining propulsive anterior-posterior impulse. For the practitioner, the results can be useful in the selection of pole length when the aim is to increase thrust phase duration, anterior-posterior force impulse and velocity.

  • 247.
    Nilsson, Johnny
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Karlsen, Jon
    A new device for evaluating distance and directional performance of golf putters.2006In: Journal of Sports Sciences, ISSN 0264-0414, E-ISSN 1466-447X, Vol. 24, no 2, p. 143-7Article in journal (Refereed)
    Abstract [en]

    The purpose of this study was to construct and evaluate the reliability of an apparatus for testing golf putters with respect to distance and direction deviation at different impact points on the clubface. An apparatus was constructed based on the pendulum principle that allowed putter golf clubs to swing at different speeds. The mean speed of the club head before ball impact, and of the ball after impact, was calculated from time measurements with photocells. A pin profile rig was used to determine the directional deviation of the golf ball. Three different putters were used in the study, two that are commercially available (toe-heel weighted and mallet types) and one specially made (wing-type) putter. The points of impact were the sweet spot (as indicated by the manufacturer's aim line), and 1, 2 and 3 cm to the left and right of the sweet spot. Calculation of club head speed before impact, and of ball speed after impact (proportional to distance), showed errors < or = 0.5% of interval duration. The variability in ball impacts was tested by measuring time and direction deviations during 50 impacts on the same ball. The mean duration (+/- s) after ball impact in the test interval (1.16 m long) was 206 (0.8) ms and the standard deviation in the perpendicular spreading of the balls in relation to the direction of the test interval was 0.005 m. A test-retest of one putter on two consecutive days after remounting of the putter on the test apparatus showed less than 1% difference in distance deviation. We conclude that the test apparatus enables a precise recording of distance and direction deviation in golf putters as well as comparisons between different putters. The apparatus and set-up can be used in the laboratory as well as outdoors on the putting green.

  • 248.
    Nilsson, Johnny
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Karlöf, Lars
    Jakobsen, Vidar
    A new device for measuring ski running surface force and pressure profiles2013In: Sports Engineering, ISSN 1369-7072, E-ISSN 1460-2687, Vol. 16, no 1, p. 55-59Article in journal (Refereed)
    Abstract [en]

    The pressure/force acting between the running surface of a ski and the snow may indirectly change glide friction. Thus, measuring the pressure/force distribution may be important for a deeper understanding of glide in skiing. The present aim was to construct a device that allowed the pressure/force underneath the ski running surface (SRS) to be recorded. Pressure sensors were attached on top of a platform. Sheets of different materials were used to improve the interaction between the SRS and the sensors. Possible functions of the device are demonstrated in three applications that emphasized comparison of force distribution underneath skis selected for similarity, force distribution under both skis and a single ski as well as backward weight distribution. The results show that the device with the pressure sensors mapped pressure/force distribution underneath the skis in the applications presented, and the system can thus be a useful tool for further optimizing e.g., ski designs.

  • 249.
    Nilsson, Johnny
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Stokes, V P
    Thorstensson, Alf
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    A new method to measure foot contact.1985In: Journal of Biomechanics, ISSN 0021-9290, E-ISSN 1873-2380, Vol. 18, no 8, p. 625-7Article in journal (Refereed)
    Abstract [en]

    A new method to measure foot contact is described. It consists of a pressure sensitive transducer attached to one end of a flexible silicone rubber tube. A reliable indicator of foot contact is obtained with the tube glued to the outer perimeter of the sole of a shoe.

  • 250.
    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.

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