REF-1083 · Nicolò et al., 2015 · Journal of Sports Sciences, · Paper · PubMed

Respiratory frequency is strongly associated with perceived exertion during time trials of different duration

9 well-trained male cyclists, self-paced 10-, 20- and 30-min time trials: RPE and breathing rate (fR) rose almost linearly and, on relative time, followed the same course in every trial, while minute ventilation, VO2 and heart rate did not; fR was the best correlate of RPE among the variables measured

Blimited evidenceMeasured on trained to highly trained athletesWritten before October 2026, being re-checked

Looking for more insight into how respiratory frequency (fR) relates to the rating of perceived exertion (RPE), the study examined whether the length of a self-paced effort changes perceptual and physiological responses. In all three time trials RPE and fR climbed almost linearly with time, and when plotted against relative duration their curves overlapped, which was not the case for minute ventilation, VO2 and heart rate. Content from the abstract only.

Participants

n=9 well-trained competitive male cyclists, 23 ± 3 years.

Protocol

Preliminary incremental ramp test.
Three randomised self-paced time trials (TTs) differing in duration: 10, 20 and 30 min.
Measured: RPE, respiratory frequency (fR), minute ventilation (VE), VO2 and heart rate (HR), expressed against absolute and relative exercise duration.

Key Results

RPE and fR both rose almost linearly with time, climbing more slowly the longer the trial lasted in absolute terms.
Against relative exercise duration, no between-trial differences in either RPE or fR.
Against relative exercise duration, between-trial differences were observed for VE, VO2 and HR.
Exercise duration did not alter how RPE related to fR, whereas it did alter how RPE related to VE and to HR.
Authors' conclusion: whatever the exercise duration, fR — and not VE, HR or VO2 — tracks RPE closely and follows a similar time course, making fR the best correlate of RPE in self-paced exercise, at least among the variables measured and over the durations tested.

Practical Application

"Does my breathing rate tell me how hard I'm going?" In 9 well-trained male cyclists riding self-paced 10-, 20- and 30-min time trials, breathing rate (fR) followed perceived exertion with the same time course in every trial, while heart rate, minute ventilation and VO2 did not; fR was the best correlate of RPE among the measures. In a self-paced hard effort, breathing rate moves with effort; heart rate lags it.
Inference, not tested here: a breathing-rate trace from a chest strap or wearable (e.g. one that records breaths per minute into a FIT file) is a candidate objective record of how hard a self-paced effort felt, read against the athlete's own earlier efforts, not against a table.
Inference, not tested here: it supports reading effort from breathing in the field — the reasoning behind the talk test (SYNTH-40) — but speech was not measured, and these were 10-30 min maximal self-paced efforts, not easy or long rides.
Not a domain marker late in a long ride: after 2 h of moderate cycling, breathing frequency at the first ventilatory threshold rose while ventilation stayed stable (REF-180); a rising breathing rate there may reflect effort rising, not the same boundary.

Limitations

n=9, men only, well-trained cyclists; ergometer time trials of 10-30 min.
Correlational: fR tracking RPE does not show that breathing drives effort perception, nor the reverse.
Self-paced maximal efforts only; constant-load, interval, easy and long sessions were not tested here.
How fR was measured and the strength of the correlations are not given in the abstract.
How this entry was checked and changed
Why this level

crossover <15 (n=9), correlational