Determination and validity of critical velocity as an index of swimming performance in the competitive swimmer

SummaryThe purpose of this investigation was to test whether the concept of critical power used in previous studies could be applied to the field of competitive swimming as critical swimming velocity (νcrit). The νcrit, defined as the swimming velocity over a very long period of time without exhaustion, was expressed as the slope of a straight line between swimming distance (dlim) at each speed (with six predetermined speeds) and the duration (tlim). Nine trained college swimmers underwent tests in a swimming flume to measure νcrit at those velocities until the onset of fatigue. A regression analysis ofdlim on trim calculated for each swimmer showed linear relationships (r2>0.998,P<0.01), and the slope coefficient signifying νcrit ranged from 1.062 to 1.262 m · s−1 with a mean of 1.166 (SD 0.052) m · s−1. Maximal oxygen consumption ( $$\dot VO_{2\max } $$ ), oxygen consumption ( $$\dot VO_2 $$ ) at anaerobic threshold, and the swimming also velocity at the onset of blood lactate accumulation (νOBLA) were also determined during the incremental swimming test. The νcrit showed significant positive correlations with $$\dot VO_2 $$ at anaerobic threshold (r=0.818,P<0.01), νOBLA (r=0.949,P<0.01) and mean velocity of 400m freestyle (r=0.864,P<0.01). These data suggested that νcrit could be adopted as an index of endurance performance in competitive swimmers.