Effect of an Adjustable Pedal Shaft on ROM and Phasic Muscle Activity of the Knee during Bicycling.
From the Department of Physical Therapy, Louisiana State University Medical Center, New Orleans, LA. The purpose of this study was to determine if a shortened pedal shaft in comparison to a standard length pedal shaft significantly changed the amount of flexion required at the knee joint during cycling. In addition, was the phasic activity of the lower extremity musculature altered as a result of cycling under the two different conditions? Six healthy subjects pedaled at a steady rate of 75 rpm on a stationary bicycle with a standard (17.0 cm) and a shortened (8.9 cm) pedal shaft. The results of a paired t-test showed that significantly (p < 0.05) less knee flexion was needed with the shortened pedal shaft compared to the standard length shaft. Comparison of each muscle's phasic activity showed similar activity patterns between the two conditions. The onset of EMG activity, however, was found to be significantly later (p < 0.05) in the rectus femoris muscle while pedaling with the shortened shaft. In addition, the termination of EMG activity in the gastrocnemius muscle was found to occur significantly sooner (p < 0.05) during the shortened pedal shaft condition. The results of this study indicate that a shortened bicycle pedal shaft reduces the amount of knee flexion required for cycling without greatly altering the muscle contraction patterns of the muscles studied. It is the opinion of the authors that such a device will allow patients with moderately restricted ROM of the knee to utilize a stationary bicycle in their rehabilitation program. J Orthop Sports Phys Ther 1989;11(6):259-262.
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