Validity of a single lactate measure to predict fixed lactate thresholds in athletes.

This study aimed to validate the use of a single blood lactate concentration measure taken following a 12 km h running stage (BLC) to predict and monitor fixed blood lactate concentration (FBLC) thresholds. Three complementary studies were undertaken. Study I: the relationships between BLC and the running speeds at FBLC of 3 mmol L (S3mM) and 4 mmol L (S4mM) measured during a multistage running field test were examined in 136 elite athletes. Study II: data from 30 athletes tested one year apart were used to test the predictive capacity of the equations obtained in Study I. Study III: 80 athletes were tested before and after an intensified training period to examine whether training-induced changes in FBLC thresholds could be predicted and monitored by BLC. Study I: BLC was significantly (P < 0.001) and inversely related to S3mM (R = 0.89) and S4mM (R = 0.95). Study II: prediction models yielded robust correlations between the estimated and measured FBLC thresholds (r = 0.94-0.99; P < 0.001). Study III: estimated changes predicted actual training-induced changes in FBLC thresholds (r = 0.81-0.91; P < 0.001). This study gives empirical support to use a single lactate measure during a sub-maximal running field test as a simple, low-cost and practical alternative to FBLC thresholds in athletes.