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Age-associated changes in muscle activity during isometric contraction

Authors

  • Sridhar P. Arjunan PhD,

    Corresponding author
    • Biosignals Laboratory, School of Electrical and Computing Engineering, Royal Melbourne Institute of Technology University, Melbourne, Australia
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  • Dinesh K. Kumar PhD

    1. Biosignals Laboratory, School of Electrical and Computing Engineering, Royal Melbourne Institute of Technology University, Melbourne, Australia
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Correspondence to: S. P. Arjunan; e-mail: sridhar.arjunan@rmit.edu.au

Abstract

Introduction: We investigated the effect of age on the complexity of muscle activity and the variance in the force of isometric contraction. Methods: Surface electromyography (sEMG) from biceps brachii muscle and force of contraction were recorded from 96 subjects (20–70 years of age) during isometric contractions. Results: There was a reduction in the complexity of sEMG associated with aging. The relationship of age and complexity was approximated using a bilinear fit, with the average knee point at 45 years. There was an age-associated increase in the coefficient of variation (CoV) of the force of muscle contraction, and this increase was correlated with the decrease in complexity of sEMG (r2 = 0.76). Conclusions: There was an age-associated increase in CoV and also a reduction in the complexity of sEMG. The correlation between these 2 factors can be explained based on the age-associated increase in motor unit density. Muscle Nerve 47: 545–549, 2013

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