Does critical swimming velocity represent exercise intensity at maximal lactate steady state?

Summary

The purpose of this investigation was to determine whether the critical swimming velocity (ν _crit), which is employed in competitive swimming, corresponds to the exercise intensity at maximal lactate steady state.ν _crit is defined as the swimming velocity which could theoretically be maintained forever without exhaustion and expression as the slope of a regression line between swimming distances covered and the corresponding times. A total of eight swimmers were instructed to swim two different distances (200 m and 400 m) at maximal effort and the time taken to swim each distance was measured. In the present study,ν _crit is calculated as the slope of the line connecting the two times required to swim 200 m and 400 m. vcrit determined by this new simple method was correlated significantly with swimming velocity at 4 mmol · 1⁻¹ of blood lactate concentration (r = 0.914,P < 0.01) and mean velocity in the 400m freestyle (r = 0.977,P < 0.01). In the maximal lactate steady-state test, the subjects were instructed to swim 1600 m (4 x 400 m) freestyle at three constant velocities (98010, 100% and 102070 ofν _crit). At 100%ν _crit blood lactate concentration showed a steady-state level of approximately 3.2 mmol · 1⁻ from the first to the third stage and at 98% ofν _crit lactate concentration had a tendency to decrease significantly at the fourth stage. On the other hand, at 102% ofν _crit, blood lactate concentration increased progressively and those of the third and fourth stages were significantly higher than those at 100% ofν _crit (P<0.05). These data suggest thatν _crit, which can be calculated by performing two timed, maximal effort swimming tests, may correspond to the exercise intensity at maximal lactate steady state.