Differences in blood lactate concentrations obtained during step-wise incremental
and constant running exercise at the same intensities were investigated. In addition,
the effect of endurance running at a constant intensity obtained by three different
incremental modes (OBLA-4, 6 or 8 min) on the blood lactate concentration were studied.
Eight firemen and six marathon runners performed: 1) three step-wise incremental running
(IR) treadmill tests, each consisting of either 5 x 4, 5 x 6 or 5 × 8 min, and, 2)
six 50 min constant intensity running (CR) treadmill tests. Capillary hemolyzed blood
was used for lactate determination. The blood lactate during the 5 × 4 min IR-test
was 32 % (p < 0.001) lower for the firemen and 22 % (p < 0.001) lower for the marathon
runners compared with the steady state concentration. These differences were diminished
in both groups when the 5 × 8 min IR test was used. In the marathon group, constant
intensity running at the OBLA intensities obtained by the 5 × 4, 5 × 6 and 5 × 8 min
resulted in a lactate accumulation to a mean level of 8.1 mmol · l-1. Also, the marathon runners interrupted the exercise due to maximal perceived exertion
after only 19 ± 3, 26 ± 4 and 30 ± 6 min, respectively. In the firemen group, a majority
of the subjects were able to complete the 50 min runs, despite a blood lactate accumulation
to a mean level of 7.3 mmol · l-1 at the OBLA 5 × 4 and 5 × 6 min intensities. When OBLA 5 × 8 min intensity was performed
in this groups, a steady state blood lactate concentration to a mean level of 5.3
mmol · l-1 occurred. It is concluded that step-wise incremental exercise with durations of 4
or 6 min will lead to a high risk of overestimating the maximal lactate steady state
exercise intensity and the endurance running capacity.
Key words
Blood lactate - maxLass - steady state - prediction - OBLA - accuracy
