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01.03.2012 | Original Article | Ausgabe 3/2012

European Journal of Applied Physiology 3/2012

Evidence of break-points in breathing pattern at the gas-exchange thresholds during incremental cycling in young, healthy subjects

European Journal of Applied Physiology > Ausgabe 3/2012
Troy J. Cross, Norman R. Morris, Donald A. Schneider, Surendran Sabapathy
Wichtige Hinweise
Communicated by Susan A. Ward.


The present study investigated whether ‘break-points’ in breathing pattern correspond to the first (\( G_{{{\text{EX}}_{1} }} \)) and second gas-exchange thresholds (\( G_{{{\text{EX}}_{ 2} }} \)) during incremental cycling. We used polynomial spline smoothing to detect accelerations and decelerations in pulmonary gas-exchange data, which provided an objective means of ‘break-point’ detection without assumption of the number and shape of said ‘break-points’. Twenty-eight recreational cyclists completed the study, with five individuals excluded from analyses due to low signal-to-noise ratios and/or high risk of ‘pseudo-threshold’ detection. In the remaining participants (n = 23), two separate and distinct accelerations in respiratory frequency (f R) during incremental work were observed, both of which demonstrated trivial biases and reasonably small ±95% limits of agreement (LOA) for the \( G_{{{\text{EX}}_{1} }} \) (0.2 ± 3.0 ml O2 kg−1 min−1) and \( G_{{{\text{EX}}_{ 2} }} \) (0.0 ± 2.4 ml O2 kg−1 min−1), respectively. A plateau in tidal volume (V T) data near the \( G_{{{\text{EX}}_{1} }} \) was identified in only 14 individuals, and yielded the most unsatisfactory mean bias ±LOA of all comparisons made (−0.4 ± 5.3 ml O2 kg−1 min−1). Conversely, 18 individuals displayed V T-plateau in close proximity to the \( G_{{{\text{EX}}_{ 2} }} \) evidenced by a mean bias ± LOA of 0.1 ± 3.1 ml O2 kg−1 min−1. Our findings suggest that both accelerations in f R correspond to the gas-exchange thresholds, and a plateau (or decline) in V T at the \( G_{{{\text{EX}}_{ 2} }} \) is a common (but not universal) feature of the breathing pattern response to incremental cycling.

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