Abstract
Laboratory studies of blood lactate accumulation often use a fixed time protocol to
define the onset (4 mM) of blood lactate accumulation (OBLA) or other indices of blood
lactate concentration. For practical reasons, field studies with athletes often use
a fixed distance protocol to accomplish the same goal. Whether these variations of
protocol are comparable has not been established. We studied 10 subjects in the laboratory
during fixed time (4 minute) and fixed distance (2 km) exercise protocols on a racing
bicycle attached to a wind load simulator. The fixed distance studies required 3-6
minutes to complete. We also studied the subjects during fixed distance (2 km) rides
in the field. In the laboratory there were no systematic differences in the velocity
(34.3 4.6 vs 34.2±4.6 km · hr-1), V̇O2 (2.78±0.60 vs 2.84±0.62 liters · min-1), or heart rate (159±16 vs 155±14 beats · min-1) at OBLA in the fixed time vs fixed distance protocols. The correlation coefficients
for velocity (r = 0.97), V̇O2 (r = 0.97) and heart rate (r = 0.94) further indicate the similarity of results.
In the field study there was a significant difference in velocity (29.9±4.8 vs 34.2±4.6
km · hr-1) but not heart rate (155±18 vs 155±15 beats · min-1) at OBLA versus the fixed distance laboratory study. The correlations for velocity
(r = 0.47) and heart rate (r = 0.93) support these data. The results suggest that
the practical modification of the lactate profile technique of using fixed distance
versus fixed time exercise stages does not systematically influence the outcome, at
least for exercise stage durations approximating 4 minutes.
Key words
Onset of blood lactate accumulation (OBLA) - lactic acid measurement - cycling
