The use of critical power as a determinant for establishing the onset of blood lactate accumulation.

Eight highly trained male kayakers were studied to determine the relationship between critical power (CP) and the onset of blood lactate accumulation (OBLA). Four exercise sessions of 90 s, 240 s, 600 s, and 1200 s were used to identify the CP of each kayaker. Each individual CP was obtained from the line of best fit (LBFCP) obtained from the progressive work output/time relationships. The OBLA was identified by the 4 mmol.l-1 blood lactate concentration and the work output at this level was determined using a lactate curve test. This consisted of paddling at 50 W for 5 min after which a 1-min rest was taken during which a 25-microliters blood sample was taken to analyse for lactate. Exercise was increased by 50 W every 5 min until exhaustion, with the blood sample being taken in the 1-min rest period. The exercise intensity at the OBLA for each subject was then calculated and this was compared to the exercise intensity at the LBFCP. The intensity at LBFCP was found to be significantly higher (t = 2.115, P < 0.05) than that at the OBLA of 4 mmol.l-1. These results were further confirmed by significant differences being obtained in blood lactate concentration (t = 8.063, P < 0.05) and heart rate values (t = 2.90, P < 0.05) obtained from the exercise intensity at LBFCP over a 20-min period and that of the anaerobic threshold (Th(an)) parameters obtained from the lactate/heart rate curve.(ABSTRACT TRUNCATED AT 250 WORDS)