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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.

In a previous paper, Pinna et al. [1] evidenced the use of a new breathing snorkel for respiratory data acquisition, but missed relevant information, particularly the values of dead space, and the diameter of tubes and valves. Authors refers the use of a similar snorkel as Roels et al. [2], but significant differences exists, specially the fact that it has only one breathing tube both for inspiration and expiration. This justifies its detailed and precise validation, once the possibility of mixing expired and inspired gases is not negligible. Moreover, the caliber of the tube allows one to suppose possible compromised ventilation that might impair exercise intensities closer to maximal oxygen consumption (VO2max), or harder. Furthermore, Pinna et al. [1] validated their snorkel using a small number of subjects exercising in a cycle ergometer, conflicting with their main conclusion that no unspecific testing procedures should be used for swimming physiologic monitoring.

Likewise, authors have failed to report previous studies concerning specific snorkel and valve systems for swimming VO2 assessment. Firstly, respiratory valves used for pulmonary function assessment on land were adapted for the Douglas bag method in swimming [3, 4], but, as they impose additional drag, a low-drag snorkel and valve system was developed [5]. Later, it was used for direct VO2 assessment using mixing chamber’s devices [69], and, afterwards, was upgraded [10] enabling real-time breath-by-breath data collection with a portable gas measurement system. Recently, a new AquaTrainer® snorkel was validated, presenting better air-flow, and ergonomic and comfort characteristics compared to previous models [11]. So, the use of commercially available respiratory snorkels is not recent, allowing researchers to collect data on the energy cost of exercise, time to exhaustion at the velocity corresponding to VO2max, and VO2 kinetics in swimming (cf [1214]).

Another important question is that the protocols of Pinna et al. [1] had increments each minute, independently of the activity considered. VO2max assessment protocols in swimming usually have steps of 4 min (or more), allowing muscle temperature to increase and pH to decrease, fostering an environment optimal for oxygen extraction. However, following a proper warm-up, 2–3 min of exercise has been shown to be sufficient for cardiovascular and biomechanical adaptations to occur promoting maximal oxygen extraction [15, 16]; furthermore, 200 m steps are frequently used for swimming incremental protocols [cf. 2, 79, 17]. Still, steps of 1 min duration [1] may not be sufficient to detect some of the cardiopulmonary parameters assessed in swimming monitoring (e.g. VO2max and, particularly, anaerobic threshold-AnT).

Another hot topic is the quantification of the muscle mass involved in swimming, as some studies from the 1970s (e.g., [3]) suggested that, as reported by Pinna et al. [1], swimming requires less muscle mass than running and cycling; this explains why VO2max has been considered lower in swimming than in the other two forms of exercise (despite being closer to cycling). However, Pinna et al. [1] observed that swimmers had a similar VO2max during the swimming and running tests, being even higher during swimming compared to cycling. We agree that VO2max is training-sensitive, but other explanations should appear, particularly that, at high velocities, swimmers use the lower limbs not only for balance but also for propulsion, significantly increasing the recruited muscle mass and energy expenditure comparing to previous beliefs. In recent EMG studies, a significant lower limb activity is observed [18], presenting an evident influence on the VO2 uptake values [19]; also, di Prampero’s group [20, 21] consider a muscle mass of 25 % of the total body mass for running, and 30 % for swimming. So, the statement that swimmers propel themselves using less muscle mass when swimming than when running and cycling should be treated with great caution.

Lastly, the fact that AnT was observed at a higher percentage of the maximum swimming workload (~82 %) compared to other exercise types is not a surprise, as it is accepted that it occurs at 80–85 % of maximum swimming intensity (e.g. [2]); in fact, when using the Vslope method, it was detected at 84.3 ± 8.7 % of the VO2max [22], in agreement with running (82.3 ± 3.0 %, [23]) and cycling ergometers (84.6 ± 5.1 %, [24]) studies. So, as the subjects tested were swimmers, maybe data from running, cycling, and arm-cranking are underestimated. As the differences between exercise types were more evident in AnT than in VO2max, Pinna et al. [1] argued that AnT appears to be more sensitive than VO2max for detecting training specificity, and that it is a most useful indicator of aerobic endurance performance. We fully agree with the authors, once VO2max is mostly used as an aerobic power indicator, more related with middle distance swimming efforts than with exercise around 30 min duration.


  1. 1.

    Pinna M, Milia R, Roberto S, Marongiu E, Olla S, Loi A, Ortu M, Migliaccio GM, Tocco F, Concu A, Crisafulli A (2012) Assessment of the specificity of cardiopulmonary response during tethered swimming using a new snorkel device. J Physiol Sci. doi:10.1007/s12576-012-0226-7

  2. 2.

    Roels B, Schmitt L, Libicz S, Bentley D, Richalet J-P, Millet G (2005) Specificity of VO2max and the ventilatory threshold in free swimming and cycle ergometry: comparison between triathletes and swimmers. Br J Sports Med 23:965–968

  3. 3.

    Holmér I (1972) Oxygen uptake during swimming in man. J Appl Physiol 33(4):502–509

  4. 4.

    Cazorla G, Montpetit R (1983) Niveau d’entraînement et spécificité de la consommation maximale d’oxygène chez le nageur. Motricité Humaine 1:50–55

  5. 5.

    Toussaint H, Meulemans A, De Groot G, Hollander A, Schreurs A, Vervoorn K (1987) Respiratory valve for oxygen uptake measurements during swimming. Eur J Appl Physiol Occup Physiol 56(3):363–366

  6. 6.

    Vilas-Boas JP, Santos P (1994) Comparison of swimming economy in three breaststroke techniques. In: Miyashita M, Mutoh Y, Richardson AB (eds) Medicine and science in aquatic sports. Med Sport Sci, vol 39. Karger, Basel, pp 48–54

  7. 7.

    Fernandes RJ, Cardoso CS, Soares SM, Ascensão A, Colaço PJ, Vilas-Boas JP (2003) Time limit and VO2 slow component at intensities corresponding to VO2max in swimmers. Int J Sports Med 24(8):576–581

  8. 8.

    Fernandes RJ, Billat VL, Cruz AC, Colaço PJ, Cardoso CS, Vilas-Boas JP (2005) Has gender any effect on the relationship between time limit at VO2max velocity and swimming economy? J Human Mov Stud 49:127–148

  9. 9.

    Fernandes RJ, Billat VL, Cruz AC, Colaço PJ, Cardoso CS, Vilas-Boas JP (2006) Does net energy cost of swimming affect time to exhaustion at the individual’s maximal oxygen consumption velocity? J Sports Med Phys Fitness 46(3):373–380

  10. 10.

    Keskinen KL, Rodríguez FA, Keskinen OP (2003) Respiratory snorkel and valve system for breath-by-breath gas analysis in swimming. Scand J Med Sci Spor 13(5):322–329

  11. 11.

    Baldari C, Fernandes RJ, Meucci M, Ribeiro J, Vilas-Boas JP, Guidetti L (2012) Is the new AquaTrainer® snorkel valid for VO2 assessment in swimming. Int J Sports Med. doi:10.1055/s-0032-1321804

  12. 12.

    Fernandes RJ, Vilas-Boas JP (2012) Time to exhaustion at the VO2max velocity in swimming: a review. J Human Kinet 32(1):121–134

  13. 13.

    Sousa A, Figueiredo P, Oliveira N, Oliveira J, Silva A, Keskinen K, Rodríguez FA, Machado LJ, Vilas-Boas JP, Fernandes RJ (2011) VO2 kinetics in 200-m race-pace front crawl swimming. Int J Sports Med 32(10):765–770

  14. 14.

    Reis JF, Alves FB, Bruno PM, Vleck V, Millet GP (2012) Effects of aerobic fitness on oxygen uptake kinetics in heavy intensity swimming. Eur J Appl Physiol 112(5):1689–1697

  15. 15.

    Kohrt WM, Morgan DW, Bates B, Skinner JS (1987) Physiological responses of triathletes to maximal swimming, cycling, and running. Med Sci Sports Exerc 19(1):51–55

  16. 16.

    Fernandes RJ, de Jesus K, Baldari C, de Jesus K, Sousa A, Vilas-Boas JP, Guidetti L (2012) Different VO2max time-averaging intervals in swimming. Int J Sports Med 33:1010–1015

  17. 17.

    Pyne DB, Lee H, Swanwick KM (2001) Monitoring the lactate threshold in world-ranked swimmers. Med Sci Sports Exerc 33(2):291–297

  18. 18.

    Figueiredo P, Sanders R, Gorski T, Vilas-Boas JP, Fernandes RJ (2013) Kinematic and electromyographic changes during 200 m front crawl at race pace. Int J Sports Med 34:49–55

  19. 19.

    Ogita F, Hara M, Tabata I (1996) Anaerobic capacity and maximal oxygen uptake during arm stroke, leg kicking and whole body swimming. Acta Physiol Scand 157(4):435–441

  20. 20.

    Capelli C, Pendergast DR, Termin B (1998) Energetics of swimming at maximal speeds in humans. Eur J Appl Physiol Occup Physiol 78(5):385–393

  21. 21.

    di Prampero PE, Fusi S, Sepulcri L, Morin JB, Belli A, Antonutto G (2005) Sprint running: a new energetic approach. J Exp Biol 208:2809–2816

  22. 22.

    Morais P, Cardoso C, Faria V, Rocha S, Machado L, Fernandes R, Vilas-Boas JP (2006) Oxygen uptake and ventilatory threshold in swimming. Port J Sport Sci 6(2):155–156

  23. 23.

    McLellan T, Cheung K (1992) A comparative evaluation of the individual anaerobic threshold and the critical power. Med Sci Sports Exerc 24:543–550

  24. 24.

    Dekerle J, Dupont L, Caby I, Marais GM, Vanvelcenaher J, Lavoie JM, Pelayo P (2002) Ventilatory threshold in arm and leg exercises with spontaneously chosen crank and pedal rates. Percept Motor Skill 95:1035–1046

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Correspondence to Ricardo J. Fernandes.

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Fernandes, R.J., Figueiredo, P. & Vilas-Boas, J.P. About the use and conclusions extracted from a single tube snorkel used for respiratory data acquisition during swimming. J Physiol Sci 63, 155–157 (2013).

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  • Muscle Mass
  • Anaerobic Threshold
  • Maximal Oxygen Consumption
  • Incremental Protocol
  • Lower Limb Activity