Research reportIntermittent application of hypergravity by centrifugation attenuates disruption of rat gait induced by 2 weeks of simulated microgravity

- We examined the effect of hypergravity on locomotion in rats.
- Rats that their hindlimb unloaded exhibited hyperextension in their knee and ankle during stance phase.
- Altered motions persisted after the termination of unloading.
- Intermittent exposure to normal gravity (1G) did not inhibit the gait alteration.
- Intermittent exposure to twice of gravity (2G) inhibited the gait alteration.

The effects of intermittent hypergravity on gait alterations and hindlimb muscle atrophy in rats induced by 2 weeks of simulated microgravity were investigated. Rats were submitted to hindlimb unloading for 2 weeks (unloading period), followed by 2 weeks of reloading (recovery period). During the unloading period, animals were subjected to the following treatments: (1) free in cages (Control); (2) continuous unloading (UL); (3) released from unloading for 1 hour per day (UL + 1G); (4) hypergravity for 1 h per day using a centrifuge for small animals (UL + 2G). The relative weights of muscles to the whole body weight and kinematics properties of hindlimbs during gait were evaluated. UL rats walked with their hindlimbs overextended, and the oscillation of their limb motion had become narrowed and forward-shifted after the unloading period, and this persisted for at least 2 weeks after the termination of unloading. However, these locomotor alterations were attenuated in rats subjected to UL + 2G centrifugation despite minor systematic changes in muscle recovery. These findings indicate hypergravity application could counteract the adverse effects of simulated or actual microgravity environments.