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

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 nonetheless (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°/sec on a KinCorn 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. Article: Loss of thigh muscle strength is a major problem for individuals who have sustained an injury or undergone knee surgery (4, 11, 12). In particular, lost quadriceps strength may lead to an unstable and functionally disabled knee (2, 12). Many clinical therapeutic interventions are used to help prevent quadriceps atrophy and enhance strengthening of the quadriceps muscle. These include electrical stimulation, biofeedback, and various isometric, isotonic, and isokinetic exercises (1, 2, 5, 6, 8-11, 13). Recently, Shelbourne and Nitz (14) have recommended early, closed kinetic chain exercise during rehabilitation for anterior cruciate ligament reconstruction. * Physical therapist, Progressive Physical Therapy, Mooresville, IN. When this study was conducted, Ms. Reynolds was a graduate student in athletic training at the University of Virginia, Charlottesville, VA. † Assistant professor of physical therapy, Krannert Graduate School of Physical Therapy, University of Indianapolis, Indianapolis, IN ‡ 'Associate professor, Graduate Athletic Training Education; director, Sports Medicine Research Laboratory; University of Virginia, Charlottesville, VA The step-up exercise is one closed chain activity that is frequently utilized in rehabilitation protocols for the knee (1, 9). The step-up exercise is purported to facilitate cocontraction of the quadriceps and hamstring muscles in a functional movement pattern and, more importantly, to increase quadriceps strength without anterior translation of the tibia on the femur (1, 2). Although the stepup exercise is a widely used clinical method to increase thigh strength, the authors have been unable to locate published evidence that shows the strengthening efficacy of this exercise protocol. The purpose of this study was to determine the effect of a step-up exercise protocol on quadriceps and hamstring muscle group isokinetic strength. The research hypothesis was that a six-week lateral step-up exercise program would significantly increase thigh girth and quadriceps muscle group isokinetic peak torque of the exercised extremity.