Comment on 'ventilation and blood lactate increase exponentially during incremental exercise'.

A recent paper in this journal has examined the ventilatory compensation for metabolic acidosis with increasing oxygen uptake, making extensive use of mathematical and statistical techniques. The authors conclude that '...respiratory compensation for metabolic acidosis during incremental exercise is a continuous process...'. While this may indeed be so, the following major aspects of the paper render the evidence at best dubious, surely inconclusive and perhaps even worthless: (1) The mathematical and statistical methodology is sloppy, incomplete and, at times, flawed. (2) No discontinuous model is presented for comparative purposes, only three continuous ones. (3) The authors ignore the fact that some threshold models produce smooth continuous data, and as a consequence, a good fit of a smooth continuous model cannot exclude the presence of a threshold. (4) The data in Table 5 show the amplitude parameter A of the preferred model to be not significantly different from zero. This paper draws these matters to the attention of readers of this journal, reviewers of manuscripts and other researchers, with comment and suggestion. This is done in the hope that all those concerned with mathematical and statistical methodologies will become more aware of their proper use.