Muscle Power Output into Pedals Exceeds Friction-Load Determined Power of a Cycle Ergometer

Abstract

It was hypothesized that the muscle power input created by both legs would far exceed the ergometers' constant-torque- based nominal value. It was supposed that this effect depended on the cadence and positive or negative acceleration of the eddy current brake wheel. If so, it is important to estimate the magnitude of this effect in order to protect patients who are at risk of overload. Four normally-trained subjects performed a series of tests involving ergometer pedaling with either ascending power loads in the range of 25 - 250 Watts, or a variation in cadence at intervals of 100 and 150 Watts. The ergometer's nominal power was compared to the power calculated with the measured time series recordings of the pedal force sensors and the power calculation thereof. Highly significant discrepancies were found between the nominal power load of the ergometer and the power transferred through the pedal sensors. The pedal power was up to 88% higher than the nominal loads, and there were inter-individual differences. The measured power far exceeded the nominal value by 80-166% at a low cadence of 40, and was only approximately congruent at a cadence of 55 to 65 per minute. Confirming the hypothesis, the results suggested that the excess power requirement was mainly due to acceleration power and depended on individual muscular performance. It is important to be aware of this when patients at risk undergo ergometer testing. Power estimation using a direct pedal force measurement may provide new insight into sport-specific stationary cycling science and energy metabolism.