Effectiveness of Lateral and forward Step-up Exercises among Selected Muscles: An EMG Study

Recovery of quadriceps strength is of primary concern during rehabilitation process following knee injury or surgery. The step up exercise is frequently used in rehabilitation protocol of knee which facilitate co-contraction of the quadriceps and hamstring muscle in a functional movement pattern and more importantly increase quadriceps strength without anterior translation of tibia on femur. The purpose of this study was to determine electromyographically of significant differences in level of electrical activity in vastus lateralis, rectus femoris vastus medialis and biceps femoris muscle occurred during the step up phase and step down phases of lateral step up and forward step up exercises at heights of 5, 8 and 11 inches. Twenty male subjects with no pathological condition of the knees participated in the study. Surface electrodes were used for recording, the muscle activity was taken in percentage to maximum voluntary contraction of each subject. For comparison between lateral step up and forward step up, step up phase and step down phase and comparison between different heights one tailed related 'T' test and ANOVA were used. Results revealed significant muscle activity of VM and VL during lateral step up than that of forward step up at heights of 5 inch [VL: T=3.43 (p<0.01), VM: T=3.21 (p<0.01)], 8 inch [VM: T=2.91 (p<0.01), VL: T=3.84 (p<0.01)] and at 11 inches height all muscles were significantly more active except for Biceps femoris [VL: T=2.22 (p<0.05), VM: T=4.06 (p<0.001), RF: T=2.12 (p<0.05)]. All muscles produced greater activity at the 11 inch height than the 8 inches and 5 inches at the level. In Lateral step up exercise, step up phase, produced significantly greater activity than step down, phase. In forward step up exercise, step up phase produced significantly greater activity than step down phase except for Biceps femoris. This result of this study are discussed with respect to the limited role of shear force of tibia during step up exercise. We concluded that forward step up exercise had less motor firing than lateral step up exercise so lateral step up exercise is more effective in rehabilitation particularly in the vastii muscles. A gradual increase in bench height and addition of weights to the body would increase in strength performance.