The purpose of this current study was to investigate the effect of different heel heights on lower extremity muscle activation during back-squat performance. Eight healthy active male collegiate students with back-squat experience volunteered for the study (BH: 1.83 ± 0.09m; BM: 88.45 ± 16.46kg). Each subject performed five trials of backsquat performance in four different heel height conditions (0, 0.5, 0.75, 1 inch; 1.27, 1.91, 2.54 cm, respectively) in random order. Mean muscle activations were obtained from VM, VL, MG, and LG between onset and end of a back-squat performance at 70% of 1 RM. Results indicated that LG and MG had significantly greater mean muscle activation in 0.75- and 1-inch heel height conditions than no heel height condition (P \u3c 0.01). Different heel heights had no effect on mean muscle activation at VM and VL