Greater Gastrocnemius Muscle Hypertrophy After Partial Range of Motion Training Performed at Long Muscle Lengths.

Kassiano, W, Costa, B, Kunevaliki, G, Soares, D, Zacarias, G, Manske, I, Takaki, Y, Ruggiero, MF, Stavinski, N, Francsuel, J, Tricoli, I, Carneiro, MAS, and Cyrino, ES. Greater gastrocnemius muscle hypertrophy after partial range of motion training performed at long muscle lengths. J Strength Cond Res XX(X): 000-000, 2022-Whether there is an optimal range of motion (ROM) to induce muscle hypertrophy remains elusive, especially for gastrocnemius. This study aimed to compare the changes in gastrocnemius muscle thickness between calf raise exercise performed with full ROM (FULLROM), partial ROM performed in the initial (INITIALROM), and final (FINALROM) portions of the ROM. Forty-two young women performed a calf training program for 8 weeks, 3 days·week-1, with differences in the calf raise ROM configuration. The calf raise exercise was performed in a pin-loaded, horizontal, leg-press machine, in 3 sets of 15-20 repetitions maximum. The subjects were randomly assigned to 1 of the 3 groups: FULLROM (ankle: -25° to +25°), INITIALROM (ankle: -25° to 0°), and FINALROM (ankle: 0° to +25°), where 0° was defined as an angle of 90° of the foot with the tibia. The muscle thickness measurements of medial and lateral gastrocnemius were taken by means of B-mode ultrasound. INITIALROM elicited greater medial gastrocnemius increases than FULLROM and FINALROM (INITIALROM = +15.2% vs. FULLROM = +6.7% and FINALROM = +3.4%; p ≤ 0.009). Furthermore, INITIALROM elicited greater lateral gastrocnemius increases than FINALROM (INITIALROM = +14.9% vs. FINALROM = +6.2%; p < 0.024) but did not significantly differ from FULLROM (FULLROM = +7.3%; p = 0.060). The current results suggest that calf training performed at longer muscle lengths may optimize gastrocnemius muscle hypertrophy in young women. Therefore, when prescribing hypertrophy-oriented training, the inclusion of the calf raise exercise performed with partial ROM in the initial portion of the excursion should be considered.