From full to partials: Investigating the impact of range of motion training on maximum isometric action, and muscle hypertrophy in young women

We compared maximum voluntary isometric action (MVIA), electromyographic (EMG) amplitude, and hypertrophy of rectus femoris (RF) and vastus lateralis (VL) between groups training in different ranges of motion (ROM). Fifty untrained women were randomised into control group (CON) or to perform knee extension exercise in one of the following groups (0°=extended knee): Full ROM (FULL_ROM:100°-30°), Initial ROM (INITIAL_ROM:100°-65°), Final ROM (FINAL_ROM:65°-30°), and Varied ROM (VAR_ROM: alternating between INITIAL_ROM and FINALROM). Pre- and post-training assessments included MVIA at 30º, 65º and 100º of knee flexion, during which EMG amplitude of RF and VL was recorded. Summed changes in cross-sectional area, assessed via ultrasound, were measured at four locations along muscles. Results showed greater improvements in INITIAL_ROM and VAR_ROM for MVIA at 100º (20.63%-25.5%) and FINAL_ROM and VAR_ROM for MVIA at 30º (17.28%-17.97%) compared to other groups (-2.92%-9.83% and 0.84%-3.31%, respectively). EMG response was larger in INITIAL_ROM than FINAL_ROM and CON at 100º (15.84% vs -6.61%-1.16%). FINAL_ROM had a higher EMG response than INITIAL_ROM at 30º (4.52% vs -14.95%). For hypertrophy, INITIAL_ROM, FULL_ROM, and VAR_ROM showed greatest increases (13.20%-17%). Greater MVIA gains aligned with trained ROM, leading to better VAR_ROM results. INITIAL_ROM, FULL_ROM, and VAR_ROM were more effective than FINALROM in hypertrophy.