The purpose of this investigation was to determine whether the critical swimming velocity (Vcri), which is employed in competitive swimming, corresponds to the exercise intensity at maximal lactate steady state. Vcri, is defined as the swimming velocity which could be theoretically maintained forever without exhaustion and expressed as the slope of a regression line between swimming distances covered and the corresponding times.
　A total of eight swimers 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, Vcri, is calculated as the slope of the line connecting the two times required to swim 200 m and 400 m. Vcri determined by this new simple method was correlated significantly with swimming velocity at 4 mmol/l of blood lactate concentration (r= 0.914, P< 0.01) and mean velocity in the 400 m freestyle (r= 0.977, P< 0.01).
　In the maximal lactate steady-state test, the subjects were instructed to swim 1,600 m (4 × 400 m) freestyle at three constant velocities (98%, 100% and 102% of Vcri). At 100% Vcri, blood lactate concentration showed a steady- state level of approximately 3.2 mmol/l from the first to the third stage and at 98% of Vcri lactate concentration decreased significantly at the fourth stage. On the other hand, at 102% of Vcri, blood lactate concentration increased progressively and those of the third and fourth stages were significantly higher than those at 100% of Vcri (P< 0.05). These data suggest that Vcri, which can be calculated by performing two timed, maximal effort swimming tests, may correspond to the exercise intensity at maximal lactate steady state.

DESCENTE SPORTS SCIENCE Vol.15/THE DESCENTE AND ISHIMOTO MEMORIAL FOUNDATION FOR THE PROMOTION SPORTS SCIENCE