Influence of motor imagery of isometric flexor hallucis brevis activity on the excitability of spinal neural function.

PURPOSE: This study aimed to validate the preliminary steps of motor image voluntary training in patients who are prone to falling as toe flexion muscle strength decreases.

MATERIALS AND METHODS: We recorded the F-wave in 30 healthy subjects (20 men, 10 women; mean age, 22.5 ± 2.1 years). First, in a resting condition, the muscle was relaxed during the F-wave recording. Subsequently, the motion of the left flexor hallucis brevis muscle is photographed. F-waves were recorded immediately and at 5, 10, and 15 min after motor imagery. The amplitude of the F/M ratio and persistence were measured. The intervention group watched the exercise task video used for F-wave measurement daily for 1 month, whereas the non-intervention group did not. The second measurement was performed 1 month later in each group.

RESULTS: In the first measurement of the amplitude of the F/M ratio in both intervention and non-intervention groups, the image condition was significantly increased compared with the resting condition, but there was no significant difference in persistence. A significant decrease in the amplitude of the F/M ratio after image conditioning was observed in the second measurement of the intervention group.

CONCLUSION: Although spinal nerve function excitement was enhanced during motor imagery, movement suppression was promoted, and spinal nerve excitability was suppressed when repeating the simple task. In the future, gradually upscaling the difficulty level of the toe flexion motor task used in the motor image may be necessary to prevent falls.