Influence of temperature and protocol on the calibration of the Computrainer electromagnetically-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 38°C). 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 (15° and 20°C) 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 38°C) (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.