VO2 Kinetics During Heavy and Severe Exercise in Swimming

Abstract The purpose of this study was to describe the VO 2 kinetics above and below respiratory compensation point (RCP) during swimming. After determination of the gas-exchange threshold (GET), RCP and VO 2max , 9 well-trained swimmers (21.0±7.1 year, VO 2max =57.9±5.1 ml.kg − 1 .min − 1 ), completed a series of “square-wave” swimming transitions to a speed corresponding to 2.5% below (S − 2.5% ) and 2.5% above (S +2.5% ) the speed observed at RCP for the determination of pulmonary VO 2 kinetics. The trial below (~2.7%) and above RCP (~2%) was performed at 1.28±0.05 m.s − 1 (76.5±6.3% VO 2max ) and 1.34 0.05 m.s − 1 (91.3±4.0% VO 2max ), respectively. The time constant of the primary component was not different between the trials below (17.8±5.9 s) and above RCP (16.5±5.1 s). The amplitude of the VO 2 slow component was similar between the exercise intensities performed around RCP (S − 2.5% =329.2±152.6 ml.min − 1 vs. S +2.5% =313.7±285.2 ml.min − 1 ), but VO 2max was attained only during trial performed above RCP (S -2.5% =91.4±5.9% VO 2max vs . S +2.5% =103.0±8.2% VO 2max ). Thus, similar to the critical power during cycling exercise, the RCP appears to represent a physiological boundary that dictates whether VO 2 kinetics is characteristic of heavy- or severe-intensity exercise during swimming.