About the use and conclusions extracted from a single tube snorkel used for respiratory data acquisition during swimming.

Pinna et al. (J Physiol Sci, 10.1007/s12576-012-0226-7, 2012) showed that a tethered swimming incremental protocol leads to higher maximal oxygen consumption values than during cycle ergometer and arm-crank tests, and evidenced that anaerobic threshold occurred at higher workloads during swimming comparing to other types of exercise. This is an interesting study in the field of exercise physiology applied to swimming that deserves merit once: (1) it employs direct gas exchange measurements during swimming, a rather hard task due to the characteristics of the water environment and the usual constraints imposed by the evaluation equipment, and (2) the physiologic comparison between swimming, running, cycling, and arm-cranking is complex, confirming that laboratory testing procedures are inadequate to estimate maximal oxygen consumption, maximal heart rate, and anaerobic threshold in swimming. However, in this Letter to the Editor, we would like to evidence some points that, in our opinion, are underdeveloped and not sufficiently clear, principally the incomplete description of the new breathing snorkel used, the non-reference to previous studies that used other snorkel models and obtained relevant data on oxygen uptake in swimming, and the assumption that swimmers uses less muscle mass when swimming than when running and cycling.