Abstract
FASCM Sponsor: Dr. Kyle Timmerman Background: Physical activity (PA) is a vital behavior to maximize health and wellness. Less is understood regarding the impact of muscle disuse on children, specifically during key stages of skeletal muscle development. The time frame between weaning and sexual maturation is known to be a critical period of development in mice. PURPOSE: We propose that, similar to malnutrition, exposure to muscle disuse early in life will impair growth rate, muscular function and tissue composition. METHODS: We exposed postnatal mice (3-4 weeks old) to 2 weeks of physical inactivity (PIA) in the form of hindlimb unloading (HU) and small mouse cage (SMC) after weaning. Grip strength and body composition were assessed before inactivity and after the inactivity period. RESULTS: Growth rate, assessed as the change in body weight, was 10.18 ± 1.31 g, 6.94 ± 0.46 g, and 5.078 ± 0.59 g for Control, SMC and HU mice (HU < CON: P < 0.05). Average lean mass change in Control was 8.02 ± 0.86 g, 5.57 ± 0.85 g in SMC, and 4.10 ± 0.39 g in HU, between weeks 3 and 5 (HU and SMC < CON: P < 0.01). Absolute max grip strength percent change between weeks 3 and 5 was 108.0 ± 9.34%, 65.76 ± 9.89%, and 55.93 ± 29.54% for Control, SMC and HU, respectively (SMC < CON: P < 0.05). More data will be added for the conference. CONCLUSIONS: Mice subjected to physical inactivity displayed lower growth rates, percent change in max grip strength, and lean mass change compared to control mice. Comparing HU and SMC, HU mice appear to have lower body weight, grip strength and lean mass than SMC mice. Changes in lean mass and body weight suggest significant deficits in physical health that may have bearing on healthy development and aging. Additionally, since grip strength is a strong predictor of health status, reduced functionality, and early mortality, these findings of premature dynapenia (muscle weakness) as a result of early life muscle disuse are concerning. Supported by: Education, Health, and Society Research Seed Grant
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