Electromyographic timing analysis of forward and backward cycling

Purpose: Backward walking to running progressions are becoming a popular, n ontraditional component of functional knee rehabilitation programs. The pur pose of this electromyographic (EMG) and motion analysis study was to compa re the activation duration of the vastus medialis, vastus lateralis, rectus femoris, medial hamstrings, lateral hamstring, tibialis anterior, and gast rocnemius muscles during forward and backward cycling. We hypothesized that the hamstrings would demonstrate greater activation duration during backwa rd cycling. Methods: The right lower extremity of 12 healthy subjects (6 ma le and 6 female) was instrumented with surface EMG electrodes and retrorefl ective markers to confirm lower extremity kinematic consistency between con ditions. Results: Statistical analysis of hip, knee, and ankle kinematics ( 200 Hz sampling rate) and gender failed to reveal significant differences b etween conditions (P > 0.05). Quadrant analysis of muscle activation durati on with Bonferroni corrections for multiple comparisons revealed that media l and lateral hamstring activation duration was greater during the early re covery phase (quadrant III) of backward cycling than forward cycling (P = 0 .00156). Rectus femoris activation duration was greater in the early propul sive phase of backward cycling (quadrant I) (P < 0.00156) and in the early recovery phase of forward cycling (quadrant III) (P < 0.00156). Conclusions : These findings lend support for the use of backward cycling during the ea rly recovery phase (quadrant III) to achieve a selective hamstring muscle r esponse of relatively decreased patellofemoral stress and anterior cruciate ligament strain.