Unilateral immobilization affects contralateral rat gastrocnemius muscle architecture.

In order to study the effects of unilateral short length immobilization on the contralateral gastrocnemius muscle (GM), length measurements were conducted on photographs taken in the active condition (tetanic plateau). Comparison of geometry of experimental and control muscles was made at optimum muscle length. The results show that a process occurred in the muscle which can be ascribed predominantly in terms of atrophy. This atrophy did not reach a maximum after 4 weeks but gradually increased in time. The altered conditions imposed on the muscle changed its architecture. It was shown that variables of the contralateral GM muscle are not representative of those of normally used muscles and should therefore not be used as control muscles for the determination of immobilization effects.