Effects of squat training with different depths on lower limb muscle volumes

Purpose The purpose of this study was to compare the effects of squat training with different depths on lower limb muscle volumes. Methods Seventeen males were randomly assigned to a full squat training group (FST, n = 8) or half squat training group (HST, n = 9). They completed 10 weeks (2 days per week) of squat training. The muscle volumes (by magnetic resonance imaging) of the knee extensor, hamstring, adductor, and gluteus maximus muscles and the one repetition maximum (1RM) of full and half squats were measured before and after training. Results The relative increase in 1RM of full squat was significantly greater in FST (31.8 +/- 14.9%) than in HST (11.3 +/- 8.6%) (p = 0.003), whereas there was no difference in the relative increase in 1RM of half squat between FST (24.2 +/- 7.1%) and HST (32.0 +/- 12.1%) (p = 0.132). The volumes of knee extensor muscles significantly increased by 4.9 +/- 2.6% in FST (p < 0.001) and 4.6 +/- 3.1% in HST (p = 0.003), whereas that of rectus femoris and hamstring muscles did not change in either group. The volumes of adductor and gluteus maximus muscles significantly increased in FST (6.2 +/- 2.6% and 6.7 +/- 3.5%) and HST (2.7 +/- 3.1% and 2.2 +/- 2.6%). In addition, relative increases in adductor (p = 0.026) and gluteus maximus (p = 0.008) muscle volumes were significantly greater in FST than in HST. Conclusion The results suggest that full squat training is more effective for developing the lower limb muscles excluding the rectus femoris and hamstring muscles.