Metabolic and ventilatory thresholds assessment in front crawl swimming

Aim: The purpose of this study was to assess and characterize the ventilatory anaerobic threshold in swimming, and to verify if the anaerobic metabolic threshold could be accurately estimated using ventilatory parameters. Methods: Twenty-eight national-level male swimmers performed a n x 200 m front crawl individualized intermittent incremental protocol, with 30 s rest intervals, until exhaustion. The ventilatory variables and heart rate were continuously measured using a telemetric portable gas analyser. The capillary blood samples for lactate concentration analysis were collected from the earlobe at rest, during rest intervals, and at the end of exercise. Results: No significant differences were observed between the ventilatory and metabolic thresholds for lactate concentration, heart rate and velocity (P=0.62, 0.80 and 0.78, respectively). The Bland-Altman plot revealed higher agreement between both methods for heart rate and velocity values. Ventilatory anaerobic threshold occurred at a swimming velocity corresponding to 88% of maximal oxygen uptake and lactate concentration mean values at ventilatory and metabolic thresholds were lower than 3 mmol.L^-1. Conclusion: Swimming anaerobic metabolic threshold could be accurately estimated using ventilatory parameters. Moreover, ventilatory anaerobic threshold occurred at similar %VO₂max than in other sports. The lactate concentration mean values at ventilatory and metabolic thresholds were lower than the reference value of 4 mmol.L^-1 evidencing that, in highly trained swimmers, individualized values of anaerobic threshold should be used instead of general references.