Master of Science, Miami University, 2022, Kinesiology, Nutrition, and Health
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 different levels of physical inactivity (PIA) 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) or standard mouse cage
activity (controls) after weaning. Grip strength and body composition were assessed
before inactivity and after the inactivity period. Muscle weights were collected after
completing PIA or 7D recovery. Results: Body weights and lean mass in PIA mice
(SMC and HU) were significantly (CON>SMC, P<0.001; CON>HU, P<0.0001)
attenuated compared to controls immediately following PIA. Fat mass was significantly
(P<0.0001) higher in control and SMC mice compared to HU mice after PIA. Absolute
maximum grip strength between weeks 3 and 5 was significantly (P<0.05) reduced in
SMC and HU mice after PIA. All muscle weights, except the tricep, collected in SMC
and HU mice weighed significantly less than control mice following PIA. Conclusion:
Mice subjected to physical inactivity displayed lower body weights, maximum grip
strength, and lean & fat mass 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 dynopenia (open full item for complete abstract)
Committee: Paul Reidy (Committee Chair); Paul Schaeffer (Committee Member); Kyle Timmerman (Committee Member)
Subjects: Kinesiology