PURPOSE: This study was conducted to investigate the most effective foot width for activating the lower extremity muscles during the lateral step-up and step-down motion according to three different foot positions.
METHODS: In this single-blinded comparative study, a total of 28 adults performed the lateral step-up and step-down motion with feet positioned at 100% of shoulder width, 75% of shoulder width, and 50% of shoulder width. Surface electromyography (EMG) data were collected from the gluteus maximus (Gmax), gluteus medius (Gmed), vastus lateralis (VL), vastus medialis (VM), and biceps femoris (BF).
RESULTS: The Gmax, Gmed, VL, VM and BF showed statistically significant differences according to the three feet positions (p < .05). When the feet were positioned at 100% of the shoulder width during the lateral step-up motion, all the muscle activities were greater than when the feet were positioned at 50% of the shoulder width (Gmax, +8%, p < .05; Gmed, +23.1%, p < .05; VL, +14%, p = .05; VM, +16%, p < .05; BF, +9.4%, p < .05). When the feet were positioned at 100% of the shoulder width during the lateral step- down motion, the muscle activity of Gmax, Gmed, VL, and VM was greater than when the feet were positioned at 50% of the shoulder width (Gmax, +9.4%, p < .05; Gmed, +9.5%, p < .05; VL, +16.1%, p < .05; VM, +11.3%, p < .05). CONCLUSION: During the lateral step-up and step-down motion, keeping the width between the feet the same as the shoulder width might be the most effective for activating the muscles of the lower extremity.