VO2 off transient kinetics in extreme intensity swimming

Inconsistencies about dynamic asymmetry between the on- and off-transient responses in oxygen uptake are found in the literature. therefore,the purpose of this study was to characterize the oxygen uptake off-transient kinetics during a maximal 200-m front crawl effort,as examining the degree to which the on/off regularity of the oxygen uptake kinetics response was preserved. eight high level male swimmers performed a 200-m front crawl at maximal speed during which oxygen uptake was directly measured through breath-by-breath oxymetry (averaged every 5 s). this apparatus was connected to the swimmer by a low hy-drodynamic resistance respiratory snorkel and valve system. results: the on- and off-transient phases were symmetrical in shape (mirror image) once they were adequately fitted by a single-exponential regression models,and no slow component for the oxygen uptake response was developed. mean (± sd) peak oxygen uptake was 69.0 (± 6.3) ml·kg-1·min-1,significantly correlated with time constant of the off-transient period (r = 0.76,p < 0.05) but not with any of the other oxygen off-transient kinetic parameters studied. a direct relationship between time constant of the off-transient period and mean swimming speed of the 200-m (r = 0.77,p < 0.05),and with the amplitude of the fast component of the effort period (r = 0.72,p < 0.05) were observed. the mean amplitude and time constant of the off-transient period values were significantly greater than the respective on-transient. in conclusion,although an asymmetry between the on- and off kinetic parameters was verified,both the 200-m effort and the respectively recovery period were better characterized by a single exponential regression model. © journal of sports science and medicine.