Supraspinal and Sensory Reflex Contributions to Motoneuron Modulation during Steady Contractions in Men and Women

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As we age, our functional movement declines. However, this decline is more pronounced in women than in men. Over the next 5 years, studies will be conducted where functional movement will be modeled by measures of force steadiness in young (18-25 y) and old (>75 y) men and women to quantify the role of the central and peripheral nervous system in this age-related functional decline that differs between sexes. These studies will focus on the biceps brachii muscle, which is ideal for studying how small changes in motoneuron activity impact force production, especially forearm control that is central to daily function throughout the lifespan. Experiments will use electromyography (EMG), to measure the activity of specific muscles that regulate the production of steady contractions. Studies proposed will be the first to determine single motor unit activity during functional movement and measure the length of individual muscle contractile units (fascicles) through ultrasonography in the biceps in men and women across the age span. This research will collectively further our understanding of spinal circuitry and its contribution to differential age-related decline between men and women in controlled movement. This research program will result in advanced training for 2 PhD students, 6 MSc students, and ~5 undergraduate students, enabling technical skill development in neurophysiology and anatomy techniques applicable to scientific discovery in both applied and basic sciences.