EFFECTS OF STAIR-STEPPING EXERCISE DIRECTION AND CADENCE ON EMG ACTIVITY OF SELECTED LOWER-EXTREMITY MUSCLE GROUPS

Step ergometry has become a popular treatment mode in cardiovascular f itness and knee rehabilitation programs. The following study describes the effects of forward stair stepping at 35 and 95 steps/minute and f orward and retrograde stair stepping at 60 steps/minute on the mean el ectromyographic (EMG) activity of the gluteus maximus, rectus femoris, vastus medialis, semimembranosus/semitendinosus, and gastrocnemius mu scles. Thirty-three subjects without prior lower extremity pathology p articipated in the study. Analysis of variance was used to compare mea n EMG activity during the knee extension phase of the different steppi ng conditions. Significant differences (p < 0.05) in mean EMGs of glut eus maximus, rectus femoris, vastus medialis, and gastrocnemius were n oted across all cadences. The semimembranosus/semitendinosus EMG activ ity displayed a single significant difference between the cadences of 35 and 95. The comparison between forward and retrograde stepping iden tified only one significant difference in mean EMC (semimembranosus/se mitendinosus). The effects of cadence on EMG activity should be consid ered when developing conditioning or rehabilitation programs for the l ower extremity. Faster cadences result in increased peak activity of s horter duration for the gluteus maximus, quadriceps, and gastrocnemius . There is no apparent difference in EMG activity of the hamstrings du e to cadence. Also, noting the minimal activation that occurs, stair-s tepping exercise would not be recommended for strengthening of the ham strings musculature.