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Symmetrical and Asymmetrical Standing
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Symmetrical and Asymmetrical Standing Effect on centre of pressure using a lateral reach movement Sally Cox University of Birmingham Introduction The importance of medio-lateral stability in relation to falls and balance control is recognised, but there has been limited investigation of the effect of different standing positions on lateral stability. The purpose of this study was to evaluate limits of lateral stability in two standing positions by measuring centre of pressure excursions during a lateral reach movement. Method Twelve women volunteered to take part and gave informed consent before the start of the study. Individuals recruited had no history of impaired balance control, or recent injury or pathology in their lower limbs. Subjects performed repeated lateral reach tests towards right and left sides in both symmetrical and asymmetrical standing. Centre of pressure was measured using a force platform and Vicon motion analysis software. The mean range of centre of pressure excursion during experimental tasks was calculated for antero-posterior and lateral movements.
Results Analysis of data was completed using related t-tests. A significant decrease was found in the range of lateral excursion in asymmetrical standing, for movements towards both the dominant and non-dominant sides (p < 0.05). No significant difference was found in the range of anteroposterior excursion between the two standing positions for movements towards either side. Conclusion The results demonstrate that lateral stability limits are significantly decreased in asymmetrical standing, indicating reduced postural control in this position. This reduction may be explained by the change in pelvic position and an alteration in muscle activation in asymmetrical standing. However, for individuals who have balance impairments this reduced lateral stability may be a factor in decreased balance control during transfers between sitting and standing and gait initiation. This reduced lateral stability may result in an increased risk of falling in this population. Evidence from this study supports further investigation of the limits of lateral stability in both healthy subjects and those with impaired balance ability.
Influence of Neck-Shoulder Pain on Trapezius Muscle Activity among Professional Violin and Viola Players Patrice Berque Glasgow Caledonian University Introduction Work-related musculoskeletal disorders in the neck-shoulder area are common among professional violin and viola players. Therefore the aim of this study was to investigate the influence of playing-related musculoskeletal disorders on muscle activity, by measuring electromyographic activity in the upper trapezius muscles of violin and viola players under three experimental conditions: rest condition; performance of an easy piece; performance of a difficult piece. Methods Ten professional violin and viola players from a Scottish orchestra volunteered to take part in the study. Five subjects complained of pain in the neck-shoulder region; five were pain-free. Bilateral surface electromyography was used, following submaximal reference voluntary contractions, to record the muscle activity of the upper trapezius muscles during the three experimental conditions. Subjects were randomly allocated to the conditions. A fourfactor balanced analysis of variances was performed. Results The results revealed that pain-free subjects developed more upper trapezius muscle activity than subjects experiencing neck-shoulder pain, when all conditions were grouped. The results were statistically significant (F = 4.07, df = 1, p = 0.05). Physiotherapy February 2003/vol 89/no 2
Moreover, subjects developed significantly more upper trapezius activity when progressing from rest to performance of the difficult piece (F = 36.64, df = 2, p < 0.001). Subjects with playing-related musculoskeletal disorders developed more upper trapezius activity than pain-free subjects at rest. The opposite tendency was observed for the playing conditions. The results were not statistically significant for this interaction (F = 1.85, df = 2, p = 0.169). Discussion The results suggest that redistribution of the muscle load from upper trapezius to other synergistic muscles may be a strategy used by subjects with playingrelated musculoskeletal disorders to alleviate pain or discomfort at the neck-shoulder area. Moreover, both physical load and psychological stress may contribute to the increase in upper trapezius muscle activity observed between conditions. Finally, it is possible that the increased upper trapezius muscle activity observed at rest among subjects with playingrelated musculoskeletal disorders may be secondary to impaired microcirculation in the upper trapezius muscle. Conclusion The voluntary monitoring of shoulder muscle activity may be of great importance in the prevention of playing-related musculoskeletal disorders.
Symmetrical and Asymmetrical Standing Effect on centre of pressure using a lateral reach movement Sally Cox University of Birmingham Introduction The importance of medio-lateral stability in relation to falls and balance control is recognised, but there has been limited investigation of the effect of different standing positions on lateral stability. The purpose of this study was to evaluate limits of lateral stability in two standing positions by measuring centre of pressure excursions during a lateral reach movement. Method Twelve women volunteered to take part and gave informed consent before the start of the study. Individuals recruited had no history of impaired balance control, or recent injury or pathology in their lower limbs. Subjects performed repeated lateral reach tests towards right and left sides in both symmetrical and asymmetrical standing. Centre of pressure was measured using a force platform and Vicon motion analysis software. The mean range of centre of pressure excursion during experimental tasks was calculated for antero-posterior and lateral movements.
Results Analysis of data was completed using related t-tests. A significant decrease was found in the range of lateral excursion in asymmetrical standing, for movements towards both the dominant and non-dominant sides (p < 0.05). No significant difference was found in the range of anteroposterior excursion between the two standing positions for movements towards either side. Conclusion The results demonstrate that lateral stability limits are significantly decreased in asymmetrical standing, indicating reduced postural control in this position. This reduction may be explained by the change in pelvic position and an alteration in muscle activation in asymmetrical standing. However, for individuals who have balance impairments this reduced lateral stability may be a factor in decreased balance control during transfers between sitting and standing and gait initiation. This reduced lateral stability may result in an increased risk of falling in this population. Evidence from this study supports further investigation of the limits of lateral stability in both healthy subjects and those with impaired balance ability.
Influence of Neck-Shoulder Pain on Trapezius Muscle Activity among Professional Violin and Viola Players Patrice Berque Glasgow Caledonian University Introduction Work-related musculoskeletal disorders in the neck-shoulder area are common among professional violin and viola players. Therefore the aim of this study was to investigate the influence of playing-related musculoskeletal disorders on muscle activity, by measuring electromyographic activity in the upper trapezius muscles of violin and viola players under three experimental conditions: rest condition; performance of an easy piece; performance of a difficult piece. Methods Ten professional violin and viola players from a Scottish orchestra volunteered to take part in the study. Five subjects complained of pain in the neck-shoulder region; five were pain-free. Bilateral surface electromyography was used, following submaximal reference voluntary contractions, to record the muscle activity of the upper trapezius muscles during the three experimental conditions. Subjects were randomly allocated to the conditions. A fourfactor balanced analysis of variances was performed. Results The results revealed that pain-free subjects developed more upper trapezius muscle activity than subjects experiencing neck-shoulder pain, when all conditions were grouped. The results were statistically significant (F = 4.07, df = 1, p = 0.05). Physiotherapy February 2003/vol 89/no 2
Moreover, subjects developed significantly more upper trapezius activity when progressing from rest to performance of the difficult piece (F = 36.64, df = 2, p < 0.001). Subjects with playing-related musculoskeletal disorders developed more upper trapezius activity than pain-free subjects at rest. The opposite tendency was observed for the playing conditions. The results were not statistically significant for this interaction (F = 1.85, df = 2, p = 0.169). Discussion The results suggest that redistribution of the muscle load from upper trapezius to other synergistic muscles may be a strategy used by subjects with playingrelated musculoskeletal disorders to alleviate pain or discomfort at the neck-shoulder area. Moreover, both physical load and psychological stress may contribute to the increase in upper trapezius muscle activity observed between conditions. Finally, it is possible that the increased upper trapezius muscle activity observed at rest among subjects with playingrelated musculoskeletal disorders may be secondary to impaired microcirculation in the upper trapezius muscle. Conclusion The voluntary monitoring of shoulder muscle activity may be of great importance in the prevention of playing-related musculoskeletal disorders.