Alves, F., Reis, J., Bruno, P. M., & Vleck, V. (June 03, 2010). Distance-time modeling and oxygen uptake kinetics in swimming. Presentation 2392 at the 2010 Annual Meeting of the American College of Sports Medicine, Baltimore, Maryland; June 2-5.

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"The slope of the linear regression between distance and time in maximal swims, the critical velocity (Cv) is a generally accepted aerobic index, however, the y-intercept in this relationship, the anaerobic distance capacity (ADC), has not shown to be consistently correlated with performance or other anaerobic capacity markers. Faster VO2 kinetics, on the other hand, have been associated with endurance performance in swimming."

This study investigated the relationships between VO2 kinetics parameters determined at heavy and severe intensities and critical velocity and anaerobic work capacity in well trained male swimmers (N = 13). Ss performed: 1) 5 x 200 m with 30 seconds rest and 5-10% velocity increments to determine velocity at maximal oxygen uptake (vVO2max), at ventilatory threshold (vVT), and OBLA; 2) two 6-minute constant velocity exercise bouts at ~25% [= VT + 0.25 x (VO2max - VT)]. All the tests were performed in front crawl with breath by breath analysis using a swimming snorkel. The parameters of the VO2 kinetics were modeled with two exponential functions. Critical velocity and anaerobic distance capacity were calculated from distance-time modeling of 200 and 400 m races, performed within one month of the other tests.

Critical velocity presented a significant correlation with vVO2max (r = 0.70), ventilatory threshold (r = 0.64), OBLA (r = 0.71), and with the primary phase time constant (T1) for heavy swimming (r = -0.8). Anaerobic distance capacity showed a low significant correlation with the primary phase time constant for severe swimming (r = 0.57).

Implication. In spite of the constraints imposed by swimming with a snorkel, aerobic markers determined using this procedure showed a high correlation with critical velocity in free swimming, supporting its concurrent validity for the physiological evaluation of swimmers. Individual VO2 kinetics responses varied according to the intensity domain which may explain the contradictory results regarding the relationship of these parameters to critical velocity and anaerobic distance capacity. Nevertheless, it seems that a slower primary phase time constant in the severe domain is associated with a higher anaerobic distance capacity, thought to represent a finite work capacity above critical velocity, confirming its dependency on the rate of VO2 on-kinetics.

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