The availability and use of stairstepping machines in both the rehabilitation and fitness industries have seen a significant increase in the last several years. The primary purpose of this study was to evaluate the electromyographic (EMG) activity levels of the rectus femoris (R), vastus medialis (V), biceps femoris (B), gastrocnemius (G), and semimembranosus/semitendonosus (S) muscles during exercise on a stepping machine and during performance of an 8-in lateral step-up. Eighteen subjects, without prior knee pathology, participated in the study. The root mean square EMG activity was obtained using surface electromyography and normalized to percent of maximum voluntary isometric contraction. Each exercise was broken down into knee flexion and knee extension phases for descriptive purposes. Analysis of variance (p < .05) was used for between exercise comparisons. Mean R and V activity were significantly greater during the lateral step-up exercise. Mean G activity was significantly greater for stepping machine exercise. Both B and S showed no significant mean differences between exercises. The stepping machine, in general, showed decreased activity during the knee extension phase and very little activity during the knee flexion phase when compared to the lateral step-up. The results indicate that exercise on the stepping machine would result in a more conservative rehabilitation approach for strengthening the quadriceps and hamstrings.
J Orthop Sports Phys Ther 1992;16(3):108-113.
Key Words: electromyography, muscle cocontraction, stairstepping