The effect of prolonged cycling on pedal forces
Sanderson DJ, Black A
The aim of this study was to determine whether cyclists modify the pattern of force application to become more effective during a prolonged ride to exhaustion. Twelve competitive male cyclists completed a steady-rate exercise ride to exhaustion at 80% of their maximum power output at 90 rev x min(-1) on a cycle ergometer. Pedal force, pedal and crank angle data were collected from an instrumented bicycle for three pedalling cycles at the end of the first and final minutes of the exercise test with simultaneous video recording of the lower limbs. Kinematic and force data were combined to compute hip, knee and ankle joint moments. There were changes in the pattern of force application, joint kinematics and joint moments of force. Comparison of the first minute and the final minute ride revealed significantly increased peak effective force (340 +/- 65.0 and 377 +/- 74.8 N for the first and final minute, respectively; F1,11 = 7.44, P = 0.02), increased positive (28.4 +/- 4.5 and 30.5 +/- 4.8 N x s for the first and final minute, respectively; F1,11 = 7.80, P = 0.02) and negative angular impulses (-1.5 +/- 1.6 and -2.4 +/- 1.5 N x s for the first and final minute, respectively; F1,11 = 4.50, P = 0.06). Contrary to our initial assumptions, it would appear that riders became less effective during the recovery phase, which increased the demand for forces during the propulsive phase. Training the pattern of force application to improve effectiveness may be a useful strategy to prolong an endurance ride.
COMMENT: This study examined how pedaling forces change as cyclists approach exhaustion while maintaining the same power. What happens is the riders became less effective on the backstroke and needed to compensate by pushing harder on the downstroke. One would presume this is due to inadequate training of the hip flexor and hamstring muscles (the prime muscles involved during the upstroke) causing them to lose ability faster than the better trained "pushing" muscles. This was confirmed in a related study by Dorel. By better training the hip flexor and hamstring muscles to become the aerobic equals of the "pushing" muscles one would expect that time to exhaustion would be extended at any given power. That is exactly what the PowerCranks do, better train these muscles.