Measurement of external power output on the Monark 864 weight ergometer

The Monark model 864 cycle ergometer is widely used for laboratory measurements of power output. The resistance is provided by a weight pan attached to a frictional belt that surrounds the flywheel. It has routinely been assumed that the frictional force between the flywheel and belt (&Fnof;) is equal to the weight of the pan (F_weight). To test this assumption, two load cells were placed in series with the frictional belt, and a direct measurement of &Fnof; was obtained by subtracting the force recordings. The measurement of &Fnof; was obtained at various pan weights with pedal cadences ranging from 25-175 rpm. The corrected values for power output were 12-14% lower than the assumed values (P<.05). The corrected values for oxygen uptake (VO₂) measurements were 7 and 14% lower for 900 and 1500 kpm/min, respectively. Since the Monark 864 is the most commonly used ergometer for performing a Wingate Anaerobic Test (WAT) the proposed method was used to correct the power output values for Wingate tests. Significant differences were found (P<.05) between corrected and uncorrected power output values at all six 5-s time intervals. Application of the correction factor yielded a 7.6% lower peak power and a 9.8% lower mean power. The corrected fatigue index value was 6% greater than the uncorrected value.