Effect of plyometric training on the fascicle length of the gastrocnemius medialis muscle

[Purpose] The present study aimed to determine the effects of eccentric calf raise exercise, which has the characteristics of plyometric training, on the fascicle length and muscle thickness of the gastrocnemius medialis muscle and range of motion of the ankle using ultrasonography. [Participants and Methods] Twenty-one healthy volunteers were randomly assigned to the eccentric calf raise exercise group or normal calf raise exercise group. Measurements were performed before training and at 3, 6, 9, and 12 weeks after training. [Results] In the eccentric calf raise exercise group, the fascicle length significantly increased after 6 weeks compared to that at baseline and at 3 weeks after training. The dorsiflexion angle and muscle thickness after three weeks significantly increased compared to that at baseline, but the pennation angle was not significantly different. The fascicle length, pennation angle, dorsiflexion angle, and muscle thickness showed no significant difference at all time points in the NCR group. [Conclusion] The results of this study showed that continued stretching of the gastrocnemius medialis muscle during eccentric calf raise exercise enhanced the morphological structures, such as the a fascicle length and muscle thickness. Eccentric calf raise exercise training may aid in injury prevention.