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Reproducibility of the instant of equality of pulmonary gas exchange and its physiological significance.

AIM
The goal of this work was to highlight the effectiveness of a new submaximal exercise index of aerobic endurance using a single incremental test: the time at which oxygen uptake and carbon dioxide output are equal, i.e., when the respiratory exchange ratio (RER)=1.00. We studied 2 experimental sets, the 1(st) to assess the reproducibility and the variability of measured variables, the 2(nd) to assess the physiological significance of the instant RER=1.00.


METHODS
The 1(st) group consisted of 8 subjects who performed 3 maximal ramp tests, the 2(nd) of 32 athletes. All subjects performed an incremental ramp test until exhaustion with determination of 1(st) and 2(nd) ventilatory and lactic thresholds (VT(1)-LT(1), VT(2)-LT(2)) and the RER=1.00 instant.


RESULTS
There was no significant difference in the used fractions of reserves (UF r) for heart rate, oxygen uptake and power output for RER=1.00 between tests, the coefficients of variation being non-significant. In group 2, there were no significant difference of UF r between VT(1) and LT(1), VT(2) and RER=1.00, LT(2) and RER=1.00. In contrast, VT(2) differed significantly from LT(2).


CONCLUSION
Measurement of the instant of equality of pulmonary gas exchange was therefore reproducible with a low intraindividual variability. Moreover, it exists a concordance of the apparitions of VT(1) and LT(1) and between these of RER=1.00 and VT(2) and LT(2). Thus, with the instant RER=1.00 provides the physiologist and the sports physician with an efficient submaximal tool to evaluate aerobic endurance of athletes using a single incremental exercise test.