Effect of unloading on muscle volume with and without resistance training

The present study aimed to investigate the effect of resistance training on the volume of four muscle groups and/or 17 individual muscles of the human lower limb during 20 days of $6^{\circ }$ head-down tilt bed rest. Twelve healthy men were divided into two groups: the resistance training group: BR-Tr $(n=6)$ and the control group: BR-Cont $(n=6)$. The volumes of the knee extensor, knee flexor, adductor, plantar flexor, and dorsiflexor muscle groups and their individual muscles were calculated. After the bed rest, the BR-Tr subjects showed no significant change in the volume in almost all tested muscles; in contrast, the volumes of the four muscle groups significantly decreased in the BR-Cont group ($-12$% to $-8$%). These results suggest that resistance training during bed rest can prevent the deteriorating of thigh muscles and calf muscles.