Electromyographic timing analysis of forward and backward cycling.

Purpose: Backward walking to running progressions are becoming a popular, nontraditional component of functional knee rehabilitation programs. The purpose of this electromyographic (EMG) and motion analysis study was to compare the activation duration of the vastus medialis, vastus lateralis, rectus femoris, medial hamstrings, lateral hamstring, tibialis anterior, and gastrocnemius muscles during forward and backward cycling. We hypothesized that the hamstrings would demonstrate greater activation duration during backward cycling.

Methods: The right lower extremity of 12 healthy subjects (6 male and 6 female) was instrumented with surface EMG electrodes and retroreflective markers to confirm lower extremity kinematic consistency between conditions.

Results: Statistical analysis of hip, knee, and ankle kinematics (200 Hz sampling rate) and gender failed to reveal significant differences between conditions (P > 0.05). Quadrant analysis of muscle activation duration with Bonferroni corrections for multiple comparisons revealed that medial and lateral hamstring activation duration was greater during the early recovery phase (quadrant III) of backward cycling than forward cycling (P < 0.00156). Rectus femoris activation duration was greater in the early propulsive phase of backward cycling (quadrant 1) (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 early recovery phase (quadrant III) to achieve a selective hamstring muscle response of relatively decreased patellofemoral stress and anterior cruciate ligament strain.