LAUSR

The ventilatory system fulfils diverse vital functions, including gas exchange and acid–base balance regulation. Such functions are guaranteed even in stressful conditions, including exercise, thus requiring a fine-control system. However, our current understanding of ventilatory control during exercise is limited. Major problems reside in the difficulty of measuring some of the inputs that regulate ventilation during ‘real’ exercise conditions and of understanding their proportional contribution to ventilation. For instance, central command (the activity of motor and premotor areas of the brain relating to voluntary muscle contraction) is a putative major regulator of ventilation, but measuring its magnitude during wholebody dynamic exercise is very challenging. Another problem that is often overlooked is thatminute ventilation ( ̇ VE) per se is not a regulated variable, being the arithmetic product of respiratory frequency (fR) and tidal volume (VT). However, little is known about the mechanisms underlying the control of fR and VT during exercise. A study published by our group (Nicolò, Marcora, Bazzucchi, & Sacchetti, 2017b) proposed an original model to shed some light on ventilatory control during exercise. To test the hypothesis that central command contributes more than metabolic inputs to regulation of fR, we manipulated recovery intensity and exercise duration during highintensity interval training. This design provided a partial dissociation of the contribution of fast and metabolic inputs to ventilation. We found that fR, but notVT, responded rapidly and in proportion to variations in work rate andwas dissociated from somemarkers of metabolic inputs. Furthermore, unlike VT, fR showed a close association with the rating of perceived exertion (RPE).We interpreted these findings as evidence that fR is regulated by fast inputs (including central command), but not bymetabolic inputs. Our interpretation that fR is regulated by central command is supported by the close association found between fR and RPE in a variety of exercise protocols and experimental conditions (Nicolò, Massaroni, & Passfield, 2017c). Indeed, central command is the main regulator of perceived exertion, as elegantly demonstrated by Zenon,