Comparison of critical swimming velocity and velocity at lactate thresholdin elite triathletes

The purpose of this study was to determine whether the critical swimming ve locity (Vcrit) corresponds to the velocity at lactate threshold (V-LT) in e lite triathletes. Eight elite triathletes (5 male, 3 female; age 26 +/- 4 y ears; height 1.7 +/- 0.1 m and body mass 75 +/- 4 kg) participated in the s tudy. Vcrit, defined as the speed that could theoretically be maintained in definitely without exhaustion, was expressed as the slope of a regression l ine between swimming distance covered and the corresponding times of five t ime trials over 100, 200, 400, 800 and 1500 m and all combinations of these . Lactate threshold (LT) was determined by visual inspection as the point o f first inflection of the lactate-work rate curve following 5 x 300 m swims of increasing velocity which were paced using the Aquapacer (Challenge and Response. Inverurie, Scotland). Velocities of the 300 m swims were - 10, - 5, 0, + 5 and + 10% of the average 100 m pace from a 1500 m time trial. Vc rit was similar regardless of the combination or number of time trials used in the linear regression. For all subjects Vcrit was significantly faster (p < 0.05) than V-LT (1.23 +/- 0.11 m.s(-1) and 1.15 +/- 0.10 m.s(-1) respe ctively). Blood lactate concentrations were also significantly higher (p < 0.05) at Vcrit (3.0 +/- 1.0 mM) than at LT (1.9 +/- 0.4 mM). Results from t he present study demonstrate that Vcrit can be calculated from any two time trials in triathletes, however Vcrit did not represent V-LT in triathletes . Since Vcrit is faster than V-LT it is unlikely to be sustained indefinite ly and consequently the notion of Vcrit should be re-evaluated in light of these findings.