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°=extended knee): Full ROM (FULLROM: 100°-30° of knee flexion); Initial Partial ROM (INITIALROM: 100°-65°); Final Partial ROM (FINALROM: 65°-30°); Varied ROM (VARROM: daily alternation between the ROM of INITIALROM and FINALROM). 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 INITIALROM group presented a greater relative increase than all groups at 70%, and at 50% and 60% the increases were greater than FINALROM, FULLROM, and non-training control (CON) groups. Moreover, FINALROM group presented similar changes compared to the CON group at 60% and 70%. In regard to 1RM, FINALROM and INITIALROM groups presented greater relative increases at the ROM trained, and no group showed greater increases than VARROM or INITIALROM, 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 VARROM group, which showed similar 1RM increases in the different ROMs tested.
Keywords: Muscle hypertrophy; excursion; partial range of motion; resistance exercise.