Effect of a Lateral Step-up Exercise Protocol on Quadriceps Isokinetic Peak Torque Values and Thigh Girth

Knee injury rehabilitation often includes the step-up exercise. However, the authors have been unable to locate documentation of the effect of the step-up exercise on lower extremity strength indices. The purpose of this study was to determine the effect of a six-week lateral step-up exercise protocol on quadriceps muscle group strength. Twenty female nonathletes (age = 20 +/- 1.5 yrs, ht = 162.6 +/- 4.9 cm, wt = 64.1 +/- 0.5 kg) were randomly assigned to a control or experimental group. Pretest concentric and eccentric strength measures were obtained at 60 degrees /sec on a Kin-Com isokinetic dynamometer. Thigh girth measurements were obtained 10 and 20 cm superior to the knee joint line. An independent t-test of the difference between pre and post isokinetic strength and girth measurements between the control and experimental groups revealed no significant difference (p > .05). In addition, no significant difference was found for the exercised and nonexercised extremity for the experimental group (p > .05). These findings suggest that this lateral step-up protocol did not provide sufficient overload to increase isokinetic strength of the quadriceps muscle group or increase thigh girth in healthy subjects. In addition, open chain assessment of muscle strength may not adequately assess strength changes incurred via closed chain exercise. Clinicians should use caution in assuming that step-up exercises provide sufficient overload to increase thigh girth or isokinetic quadriceps peak torque values. J Orthop Sports Phys Ther 1992;15(3):151-155.