KY Space Grant RIA-22-043: Interaction of Sleep Restriction and Unloading on Neuromuscular Control of Strength

NASA’s Artemis program aims to return astronauts to the lunar surface in 2024. During spaceflight, astronauts experience a complex array of physiological stimuli including unweighting and altered sleep cycles that may interact to impair muscle strength and postural control – ultimately compromising safety, health, and mission performance. During the Apollo missions, astronauts suffered at least 9 falls in 14 lunar EVA missions which may be partially due to altered muscle strength and postural control. Quadriceps strength decreases by 15% with as little at seven days unloading. Even short-term sleep restriction significantly reduces muscular strength, alters neuromuscular patterns, and impairs postural control. To date, it is unclear how these unloading and sleep restriction interact to affect muscle strength and postural control. We will perform bilateral quadriceps muscle imaging, interpolated twitch, and postural control assessment before and after unilateral lower limb suspension (ULLS) with and without sleep restriction in a matched pairs randomized study design. We hypothesize that ULLS and SR additively reduce quadriceps’ maximal voluntary strength, voluntary activation, and neuromuscular efficiency, and muscle mass. We further hypothesize that ULLS and SR will additively increase postural sway. This collaborative project among researchers from the University of Kentucky and University of Louisville will provide valuable mentorship for multiple new and early-stage investigators from an established, NASA-aligned Co-I. Importantly, this project lays the foundation for future investigations exploring the role of sleep restriction in various aspects of physical deconditioning, muscle remodeling, and sensorimotor function during prolonged spaceflight.