The dynamic behaviour of pulmonary gas exchange variables (particularly oxygen uptake – VO2) during and after exercise has been studied throughout different exercise modes (Sousa et al., 2015). However, from the time VO2 is measured (usually at the mouth using a breath-by-breath gas analyser – e.g. K4b2, Cosmed, Italy), until is available for coaches (for training control and athletes evaluation), a complex system involving multi-level dynamics experimental steps must occur.
Firstly, individual breath-by-breath VO2 data that typically arises as a result of some constraints caused by the traditional facemask or respiratory snorkel and valve system used, like swallowing, coughing, sighing, signal interruptions and so forth, should be omitted. For that, respiratory frequency (Rf – b/min), tidal volume (TD – l), oxygen expiratory fraction (FeO2 – %) and carbon dioxide expiratory fraction (FeCO2 – %) breath-by-breath values greater and lower than 4 SD from the local mean are not considered for further analysis. Secondly, individual breath-by-breath VO2 responses are smoothed using a 3-breath moving average. After this process, multiple analysis strategies, fundamentally by averaging across breaths and discrete time intervals, are used. We recommend the 10 and 15 s time-averaging intervals strategies to more precisely assess the VO2 values.
The emergence of breath-by-breath gas analysers enabled the acquisition of pulmonary data with greatest temporal resolution (de Jesus et al., 2014). However, attention should be given to this dynamic process, which should provide the best compromise between the accuracy and the reliability in pulmonary assessment.


Kelly de Jesus
Leandro Machado
João Paulo Vilas Boas
Ricardo Fernandes

Ecological Approach of Sport and Sport Education e-session


Photos by : David Rytell