Motor unit function: central descending and sensory reflex modulation

点击翻译按钮获取中文摘要

It is understood that muscle strength is lower, force steadiness decreases and functional ability declines with advancing age.  The mechanisms of these changes have not been clearly elucidated and until recently gender differences were not recognized.  Because purposeful movement is merely a combination of lengthening and shortening contractions, it is imperative to understand MU activity of the agonist and antagonist during these simple activities. The overall objectives of these experiments are to identify and determine the contributions of central descending and sensory reflex pathways to the modulation of motor neuron activity and subsequent effect on force control in the quadriceps of young and old women. Our working hypothesis is that sensory feedback and central descending pathways work collectively to code MU output (recruitment, discharge rate, synchronization and coherence of MUs), however this 'collective coding' differs between contraction types (isometric, lengthening, shortening) and is altered with age. Moreover, because there are differential age-related declines between men and women in functional ability and strength and both of these elements are closely linked to MU activity it is plausible that a gender difference in MU activity might exist.  To my knowledge, to date, MU activity has not been purposely studied in healthy young and old women.  These studies will not only characterize agonist and antagonist MU activity during anisometric quadriceps contractions in women, but contribute to our understanding of the contribution of sensory reflex and supraspinal descending input on MU activity and age-related alterations in force control.