REF-1084 · Nicolò et al., 2017 · Frontiers in Physiology, · Paper · PubMed · Free full text

Respiratory Frequency during Exercise: The Neglected Physiological Measure

A Perspective article: unlike heart rate, VO2 and blood lactate, respiratory frequency (fR) is strongly associated with perceived exertion across many exercise paradigms and under muscle fatigue, glycogen depletion, heat and hypoxia, and responds rapidly to workload changes in HIIT, so the authors propose fR as a strong marker of physical effort for training monitoring; an opinion piece, no new data

C+thin evidenceMeasured on a mixed groupWritten before October 2026, being re-checked

The authors argue that respiratory frequency (fR), although measurable with unobtrusive wearables of relatively good accuracy, is rarely monitored in training and has mostly been used to estimate the ventilatory threshold.

They present evidence that fR, unlike heart rate, VO2 and blood lactate, is strongly associated with perceived exertion across a variety of exercise paradigms and experimental interventions, and that it responds rapidly to workload changes during high-intensity interval training. Content from the abstract only.

Participants

None — Perspective article.

Protocol

The article aims to (i) present scientific evidence for the relevance of fR in training monitoring; (ii) critically review methods for measuring fR and the accuracy of currently available respiratory wearables; (iii) give preliminary indications on how to analyse fR data.

Key Results

Unlike heart rate, VO2 and blood lactate, fR is strongly associated with perceived exertion during a variety of exercise paradigms, and under several interventions affecting performance: muscle fatigue, glycogen depletion, heat exposure and hypoxia — the authors take this to suggest fR is a strong marker of physical effort.
Unlike other physiological variables, fR responds rapidly to variations in workload during HIIT.
fR is already measured as a vital sign by multiparameter wearables in military, clinical and occupational settings; in exercise it has mostly been used to estimate the ventilatory threshold.
No numerical results are given in the abstract.

Practical Application

"Is breathing rate worth watching in training?" A Perspective from the group that published the time-trial study ([REF-1083]) argues that breathing rate tracks perceived effort across exercise types and under fatigue, glycogen depletion, heat and hypoxia — where heart rate, VO2 and lactate do not — and that it follows workload changes in intervals faster than other physiological signals. An argument from the authors' reading of the evidence (level C+), not a trial: treat breathing rate as a promising effort signal, not a validated zone system.
Inference, not tested here: in short intervals, where heart rate lags the work, a breathing-rate trace from a wearable may show the structure of the session better than heart rate does; read it against the athlete's own sessions.
Not from this paper; the base's own practice: the talk test is the field form of "read effort from breathing" for easy and long aerobic work (SYNTH-40); there are no breathing-rate zones in the base.

Limitations

Perspective / opinion article; not systematic, no pooled analysis, no risk-of-bias assessment.
The abstract does not name the studies behind each claim, their sizes, or the accuracy of the wearables discussed.
Written by researchers whose own studies form much of the evidence presented.
Wearable accuracy and analysis methods move fast; the 2017 device landscape is dated.
How this entry was checked and changed
Why this level

narrative review without systematic method