Long-term immobilization of skeletal muscle results in a loss of muscle force. Previous research has revealed that one week of immobilization affects maximum voluntary contraction (MVC), MVC potential, low-level force modulation, and corticospinal excitation. Corticomotor excitability is reduced by short-term immobilization, even over days or hours. However, the effect of 12-hour immobilization period on muscle output function is unclear. Therefore, the aim of the present study was to investigate the change in motor function after immobilization of the upper limb for 12hours.

Twenty subjects were assigned to the following two groups: immobilization, control (n=10 in each group). The left hand of the subjects in the immobilization group were wrapped with an elastic bandage and further limited the arm movement using an arm sling to the upper extremity for 12-hours. MVC during isometric abduction of the index finger, fluctuation of force (force-fluctuation) during a force modulation task, and twitch force evoked by supramaximal electrical stimulation at rest were measured before (pre-test) and after the immobilization period (post-test). The control group performed these tests, but were not immobilized. The data were analyzed using two-way (time×group) repeated measures analysis of variance.

MVC decreased significantly in the immobilization group in the post-test compared with the pre-test. Force-fluctuation increased significantly in the immobilization group in the post-test compared with the pre-test. Twitch force revealed that a significant main effect for time.

The results of the study demonstrate that MVC and force-fluctuation were affected by 12-hour immobilization period, but twitch force was not affected. These findings have significant implications for preventing declines in muscle output function with time (for example, during cast immobilization).