Mechanical power and muscle action during forward and backward running.

Recently, there has been increasing interest in using backward running (BR) as an exercise and rehabilitation tool. To date, no study has been performed that combined electromyography (EMG) and joint kinetics to study BR. The purpose of this study was to compare selected EMG and kinetic parameters in the stance phase of forward running (FR) and backward running (BR). The sagittal plane of the right knee was analyzed during three trials of FR and BR in six male subjects. Four 60-Hz video cameras collected motion data, and a link segment model of the right lower extremity was established. Force plate and EMG data were collected at 1000 Hz and synchronized with the video data. The knee muscle peak (+) and peak (-) mechanical power and total (+) and total (-) mechanical work were calculated. Electromyography signals were captured from the right lower extremity on the rectus femoris, vastus lateralis, vastus medialis, biceps femoris, gastrocnemius, and tibialis anterior muscles. Statistical analysis indicated that significantly less (p < 0.05) peak (+) and (-) power and total (+) work occurred at the knee during BR than during FR. Significant differences (p < .05) in muscle firing patterns between conditions were observed. Muscle action of the vastus lateralis (VL) and vastus medialis oblique (VMO) was largely eccentric and concentric during FR and isometric and concentric during BR. Backward running appears to be a good method for achieving isometric and concentric muscle action of the VMO and VL and may be useful in clinical conditions that require an increase in knee extensor strength.