Practical markers of the transition from aerobic to anaerobic metabolism during exercise: rationale and a case for affect-based exercise prescription

Background. The high rates of dropout from exercise programs may be attributed in part to the poor ability of most individuals to accurately self-monitor and self-regulate their exercise intensity. The point of transition from aerobic to anaerobic metabolism may be an appropriate level of exercise training intensity as it appears to be effective and safe for a variety of populations. Possible practical markers of this event were compared. Methods. Two samples of 30 young and healthy volunteers each participated in incremental treadmill tests until volitional exhaustion. The ventilatory threshold, a noninvasive estimate of the aerobic–anaerobic transition, was identified from gas exchange data. Heart rate, self-ratings of affective valence (pleasure–displeasure), perceived activation, and perceived exertion were recorded every minute. Results. In both samples, heart rate, perceived activation, and perceived exertion rose continuously, whereas the ratings of affective valence showed a pattern of quadratic decline, initiated once the ventilatory threshold was exceeded. Conclusions. Exercise intensity that exceeds the point of transition from aerobic to anaerobic metabolism is accompanied by a quadratic decline in affective valence. This marker may be useful in aiding exercisers to recognize the transition to anaerobic metabolism and, thus, more effectively self-monitor and self-regulate the intensity of their efforts.