Partial range of motion training elicits favorable improvements in muscular adaptations when carried out at long muscle lengths

The study compared changes in strength and regional muscle hypertrophy between different ranges of motion (ROM) in the knee extension exercise. Forty-five untrained women were randomized to either a control group or to perform the exercise in one of the following 4 groups (0 degrees=extended knee): Full ROM (FULLROM: 100 degrees-30 degrees of knee flexion); Initial Partial ROM (INITIAL(ROM): 100 degrees-65 degrees); Final Partial ROM (FINAL(ROM): 65 degrees-30 degrees); Varied ROM (VAR(ROM): daily alternation between the ROM of INITIAL(ROM) and FINAL(ROM)). Pre- and post-training assessments included one repetition maximum (1RM) testing in the ROM corresponding to the initial, final and full ROM, and measurement of cross-sectional areas of the rectus femoris and vastus lateralis muscles at 40%, 50%, 60% and 70% of femur length in regard to regional muscle hypertrophy. Results showed that the INITIAL(ROM) group presented a greater relative increase than all groups at 70%, and at 50% and 60% the increases were greater than FINAL(ROM), FULLROM, and non-training control (CON) groups. Moreover, FINAL(ROM) group presented similar changes compared to the CON group at 60% and 70%. In regard to 1RM, FINAL(ROM) and INITIAL(ROM) groups presented greater relative increases at the ROM trained, and no group showed greater increases than VAR(ROM) or INITIAL(ROM), regardless the ROM tested. In conclusion, partial ROM training in the initial phase of the knee extension exercise promoted greater relative hypertrophy in certain muscle regions than training in other ROM configurations, and no group promoted a greater 1RM increase than VAR(ROM) group, which showed similar 1RM increases in the different ROMs tested.