Oxygen uptake kinetics at moderate and extreme swimming intensities

Introduction: Traditionally, studies regarding oxygen consumption kinetics are conducted at lower intensities, very different from those in which the sports performance occurs. Objective: Knowing that the magnitude of this physiological parameter depends on the intensity in which the effort occurs, it was intended with this study to compare the oxygen consumption kinetics in the 200 m front crawl at two different intensities: moderate and extreme. Methods: Ten male swimmers of international level performed two tests separated by 24h: (i) progressive and intermittent protocol of 7 x 200 m, with 30 seconds intervals and with increments of 0.05m.s^-1, to determine the anaerobic threshold correspondent step; and, (ii) 200 m at maximal velocity, in both expiratory gases were continuously collected breath-by-breath. Results: Significant differences were obtained between amplitude and time constant determined in the 200 m at extreme and moderate intensities, respectively (38.53 ± 5.30 ml. kg^-1.min^-1 versus 26.32 ± 9.73 ml. kg^-1.min^-1 and 13.21 ± 5.86 s versus 18.89 ± 6.53 s (p ≤ 0.05). No differences were found in time delay (9.47 ± 6.42 s versus 12.36 ± 6.62 s, at extreme and moderate intensity, respectively (p ≤ 0.05). A negative correlation between time delay and time constant at the moderate intensity was reported (r = - 0.74, p ≤ 0.05). Conclusions: Both intensities were well described by double-exponential fittings and there were significant differences between them in terms of amplitude and time constant.