Davinder Kumar Gaur, Shweta Shenoy, Jaspal Singh Sandhu
Department of Sports Medicine and Physiotherapy, Guru Nanak Dev University, Amritsar - 143005, Punjab, India
Purpose: The purpose of the present study was to analyze the effect of aging on activation capacity of shoulder muscles, between individuals of young and older age groups, during dynamic activities of pulling, pushing, elevation and throwing activities.
Materials and Methods: Nine young male adults of 20-29 year age group and eight old male individuals of 50-59 year age group, without any shoulder problems, were studied. Signals were recorded by surface electromyography as "percentage maximum voluntary isometric contraction" from middle deltoid, posterior deltoid, supraspinatus, and infraspinatus muscles of the shoulder. The results obtained from the muscles of younger age group were compared with those of older age group. Unpaired 't' - test was used for purpose of statistical analysis.
Results: Significant increase in muscle activity was observed in elderly group as compared to younger group in activities involving pull, push, elevation and throw. Posterior deltoid (P <0.036) and infraspinatus (P <0.026) exhibited greater activity during pulling. Greater activity was observed in middle deltoid (P <0.015), supraspinatus (P <0.02) and infraspinatus (P <0.012) during pushing. During elevation posterior deltoid (P <0.02) and infraspinatus (P <0.05) were found to be more active. During throwing greater activity was observed in middle deltoid (P <0.034), posterior deltoid (P <0.05) and infraspinatus (P <0.05).
Conslusion: Greater recruitment of the selected shoulder muscles occurs, with aging, during the dynamic activity. With aging, the percentage of muscle fibers decrease, resulting in the decrease of muscle strength. This may imply that, as a compensatory mechanism, elderly individuals require greater recruitment of muscle fibers to perform an activity than younger individuals.
Clinical Relevance: Difference in recruitment pattern in the muscles of stability and mobility, between old and young individuals may be regarded as a potential factor for development of shoulder instability syndrome in elderly individuals.
Davinder Kumar Gaur
156 Sharda Niketan, Pitampura, New Delhi - 110 034
Source of Support: None, Conflict of Interest: None
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