Respiratory frequency and tidal volume during exercise: differential control and unbalanced interdependence

Differentiating between respiratory frequency (f(R)) and tidal volume (V (T)) may improve our understanding of exercise hyperpnoea because f(R) and V (T) seem to be regulated by different inputs. We designed a series of exercise manipulations to improve our understanding of how f(R) and V (T) are regulated during exercise. Twelve cyclists performed an incremental test and three randomized experimental sessions in separate visits. In two of the three experimental visits, participants performed a moderate‐intensity sinusoidal test followed, after recovery, by a moderate‐to‐severe‐intensity sinusoidal test. These two visits differed in the period of the sinusoid (2 min vs. 8 min). In the third experimental visit, participants performed a trapezoidal test where the workload was self‐paced in order to match a predefined trapezoidal template of rating of perceived exertion (RPE). The results collectively reveal that f(R) changes more with RPE than with workload, gas exchange, V (T) or the amount of muscle activation. However, f(R) dissociates from RPE during moderate exercise. Both V (T) and minute ventilation ([Formula: see text]) showed a similar time course and a large correlation with [Formula: see text] in all the tests. Nevertheless, [Formula: see text] was associated more with [Formula: see text] than with V (T) because V (T) seems to adjust continuously on the basis of f(R) levels to match [Formula: see text] with [Formula: see text]. The present findings provide novel insight into the differential control of f(R) and V (T) – and their unbalanced interdependence – during exercise. The emerging conceptual framework is expected to guide future research on the mechanisms underlying the long‐debated issue of exercise hyperpnoea.