Animal models implicate multiple mechanical factors in the initiation of exercise induced muscle injury. Muscle injury has been widely studied in humans, but few data exist regarding the underlying cause of muscle injury. This study sought to examine the role of torque per active muscle volume in muscle injury. Eight subjects performed 80 electrically stimulated (EMS) eccentric contractions of the right and left quadriceps femoris (QF) through an 80° arc at 120°/s. Specific torque was varied by applying 25 Hz EMS to one thigh and 100 Hz EMS to the contralateral thigh. T2 magnetic resonance images of the QF were collected before and 3 days after the eccentric exercise bouts. Injury was assessed via changes in isometric force and ratings of soreness over the course of 14 days after exercise, and by determining changes in T2 relaxation time and muscle volume 3 days after exercise. 100 Hz EMS induced greater force loss (P < 0. 05), soreness (P < 0.05), change in muscle volume (P = 0.03), and the volume of muscle demonstrating an increase in T2 (P = 0.005) compared to 25 Hz EMS. Additionally, injury was found to be similar across the QF in all but the most proximal regions of the femur. Our findings suggest that in humans, high torque per active volume during lengthening muscle contractions is related to muscle injury.