The effects of exercise under hypergravity and microgravity on the musculoskeletal system of mice

Abstract

Disuse muscle atrophy and bone destruction are caused by the lack of locomotive activity both in space and on Earth. Mechanical loading by exercise is effective in preventing disuse diseases and maintaining the musculoskeletal system. This review provides an overview of the changes in the musculoskeletal system of mice under varying gravitational conditions to quantitatively analyze these phenomena. The experiments performed that mice maintained normal gravity (1G) and hypergravity (2G) using a centrifugal device on Earth, as well as microgravity (µG) and artificial 1G gravity (AG) using a centrifugal device on the International Space Station (ISS Kibo). We investigated the effects of hypergravity and microgravity environments on the musculoskeletal tissues under conditions of active movement. The sequential studies revealed that exercise under both hypergravity and microgravity conditions has correlated positive and negative effects on the maintaining quality of the musculoskeletal system, suggesting that exercise with appropriate gravitational loading on active movement positively regulates the musculoskeletal system. Recently, it has become evident that disuse diseases of the musculoskeletal system, which are an active movement in the skeletal legs and occlusal jaw, cause various chain reactions not only to the locomotive system but also to the sensory organs, and brain nerves, showing the importance of preventing dementia through appropriate exercise loading. This review outlines the latest findings on mechanical control of the motor system aimed at preventing disuse diseases caused by inactivity due to aging and immobility, a concern that is expected to increase with the advent of a super-aged society.