The relationship between anaerobic threshold and heart rate linearity during cycle ergometry

Recent studies have demonstrated there is a definitive deflection in the heart rate response to incremental velocity work that coincides with the anaerobic threshold. These studies were conducted with elite athletes who performed the specific activities in which they were trained. The purpose of this study was to determine if the same relationship in heart rate and ventilatory response to increasing velocity was evident in nine untrained healthy subjects aged 22 to 36 years performing leg ergometry under controlled laboratory conditions. All subjects began pedaling at 50 rpm with an initial power output of 100 W. Pedaling rates were increased by 5 rpm every 30 s. This increment was equivalent to a power increase of 11.1 W. The subjects cycled to the point of exhaustion or until they could no longer maintain the pedaling speed at the higher velocities. Heart rate and expiration gases were collected at 30-s intervals. The results indicated that the heart rate and ventilatory response to increasing velocity as previously reported under field conditions does not exist under laboratory conditions. While there was a definitive and statistically significant inflection in the ventilatory response to increasing velocity, heart rate remained linear. Therefore, caution should be used when determining the anaerobic threshold from the single measure of heart rate response.