Influence of temperature and protocol on the calibration of the Computrainer electronically-braked cycling ergometer

Background The RacerMate Inc. CompuTrainer is an increasingly popular ergometer in Sport Science laboratories, yet there is little information on the characteristics and validity of the CompuTrainer calibration procedure. Aim To investigate the effect of a range of environmental temperatures on the CompuTrainer calibration procedure and validate the power output against an SRM powermeter. Methods A bicycle fitted with an SRM Training System was attached to a CompuTrainer ergometer. The calibration procedure was repeated (up to 5 occasions) interspaced with 2min cycling at 200W and ~90rpm. The cyclist then cycled for a further 2min at 200W for a direct comparison with the SRM training system. This process was repeated at seven different random calibration values at a range of environmental temperatures (15, 20, 28 and 38oC). Results At all temperatures there was a large decline in calibration pressure after the first 2min of cycling, with no further decline after 6min of cycling. This decline was inversely correlated with the temperature (r² = 0.7). In low temperatures (15º and 20oC) the CompuTrainer significantly underestimated SRM power by 7.3 ± 5.8 W (95%CI: 4.2-10.4W; Range 1-18W; p = 0.0002) but was similar (-0.3 ± 4.4W) in high temperatures (28° and 38oC) (95%CI: -2.7-2.0W; Range -9-5W; p = 0.78). Conclusions Both temperature and calibration procedure were shown to affect power measurement and thus these authors have suggested an alternative procedure to enhance the reliability and validity of the CompuTrainer ergometer.