Respiratory Frequency during Exercise: The Neglected Physiological Measure

Abstract

The use of wearable sensor technology for athlete training monitoring is growing exponentially, but some important measures and related wearable devices have received little attention so far. Respiratory frequency (fR), for example, is emerging as a valuable measurement for training monitoring. Despite the availability of unobtrusive wearable devices measuring fR with relatively good accuracy, fR is not commonly monitored during training. Yet fR is currently measured as a vital sign by multiparameter wearable devices in the military field, clinical settings, and occupational activities. When these devices have been used during exercise, fR was used for limited applications like the estimation of the ventilatory threshold. However, more information can be gained from fR. Unlike heart rate, trueV˙O2, and blood lactate, fR is strongly associated with perceived exertion during a variety of exercise paradigms, and under several experimental interventions affecting performance like muscle fatigue, glycogen depletion, heat exposure and hypoxia. This suggests that fR is a strong marker of physical effort. Furthermore, unlike other physiological variables, fR responds rapidly to variations in workload during high-intensity interval training (HIIT), with potential important implications for many sporting activities. This Perspective article aims to (i) present scientific evidence supporting the relevance of fR for training monitoring; (ii) critically revise possible methodologies to measure fR and the accuracy of currently available respiratory wearables; (iii) provide preliminary indication on how to analyze fR data. This viewpoint is expected to advance the field of training monitoring and stimulate directions for future development of sports wearables.

A new model of ventilatory control during exercise

“…Our interpretation that f R is regulated by central command is supported by the close association found between f R and RPE in a variety of exercise protocols and experimental conditions (Nicolò, Massaroni, & Passfield, 2017c) Remarkably, our findings suggest the existence of a differential control of f R and V T during exercise (Nicolò et al, 2017b), paving the way for a new series of studies specifically targeting the control of the two components ofV E . Along these lines, we designed a study aimed at understanding how f R and V T are regulated across different exerciseintensity domains (Nicolò, Girardi, Bazzucchi, Felici, & Sacchetti, 2018).…”

“…Our interpretation that f R is regulated by central command is supported by the close association found between f R and RPE in a variety of exercise protocols and experimental conditions (Nicolò, Massaroni, & Passfield, ). Indeed, central command is the main regulator of perceived exertion, as elegantly demonstrated by Zenon, Sidibe, and Olivier ().…”

“…The three papers highlighted in this Connections article describe the path we followed to develop our model of ventilatory control. The close association found between f R and perceived exertion in a series of studies (Nicolò et al., ) triggered our interest in understanding the mechanisms underlying this link. The study by Zenon et al.…”

“…The close association found between f R and perceived exertion in a series of studies (Nicolò et al, 2017c) triggered our interest in understanding the mechanisms underlying this link. The study by Zenon et al (2015) provided the first direct evidence that perceived exertion is regulated by central command, thus reinforcing the notion that RPE can be used as a marker of its magnitude.…”

Estimating an individual’s oxygen uptake during cycling exercise with a recurrent neural network trained from easy-to-obtain inputs: A pilot study

“…In our study, the pedalling cadence was kept constant, so it is likely that the contribution of this variable may be limited in our study. As well, respiratory frequency indicating the ventilatory response to exercise has an important link with _ VO 2 , while heart rate has additional known associations with exercising _ VO 2 [5,52].…”