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To analyze vastus medialis obliquus (VMO) and vastus lateralis (VL) muscle activity during the concentric and eccentric phases of a lateral step-up exercise.
Repeated-measures. Dependent variable: the integrated electromyogram measured as a percentage of the maximal voluntary isometric contraction of the VMO and VL muscles. Independent variable: muscle contraction with 2 levels (concentric and eccentric).
Twenty-three volunteers with no previous history of knee surgery or anterior knee pain.
Surface electrodes were positioned over the VMO and VL, and electromyographic data were collected during the exercise.
The 2 muscle phases of contraction were different when both dependent variables were considered simultaneously (F2,7 = 33.2, P < .001). Concentric contractions produced greater muscle activity for VL (P < .05) and VMO (P < .05).
Because concentric contractions produce greater activity than eccentric contractions do during the lateral step-up exercise, they provide a stronger stimulus for muscle activation, which might result in greater muscle strength gains.
The authors are with the Sports Injury Research Laboratory, Athletic Training Department, at Indiana State University,Terre Haute, IN 47809.