Neural Mechanisms of Age-Related Loss of Muscle Performance and Physical Function

BACKGROUND: This article discusses the putative neural mechanisms of age-related muscle weakness within the broader context of the development of function-promoting therapies for sarcopenia and age-related mobility limitations. We discuss here the evolving definition of sarcopenia and its primary defining characteristic, weakness. METHODS: This review explores the premise that impairments in the nervous system's ability to generate maximal force or power contribute to sarcopenia. RESULTS: Impairments in neural activation are responsible for a substantial amount of age-related weakness. The neurophysiological mechanisms of weakness are multifactorial. The roles of supraspinal descending command mechanisms, spinal motor neuron firing responsivity, and neuromuscular junction transmission failure in sarcopenia are discussed. Research/clinical gaps and recommendations for future work are highlighted. CONCLUSION: Further research is needed to map putative neural mechanisms, determine the clinical relevance of age-related changes in neural activation to sarcopenia, and evaluate the effectiveness of various neurotherapeutic approaches to enhancing physical function.