Capillary blood lactate assessment is increasingly used by well-trained runners to
monitor the intensity of endurance exercise. In order to examine the known association
of exercise intensity with blood lactate accumulation also im less trained subjects,
we analysed data from a standardized incremental maximal test on the treadmill of
319 men (age 22.9±5.5 years, [means±S.D.]) and 145 women (22.7±4.5 years) characterized
by a wide variation in endurance capacity. Results showed that the running velocity
eliciting a blood lactate comcentration of 4mmol/l did not correspond to the same
exercise intensity in well endurance-trained vs poorly endurance-traimed subjects.
At 4 mmol/l blood lactate, the slowest decile of men (i.e. 32 out of 319) ran at 71±4.7%
(corresponding to 2.9±0.3m/s) of their maximal treadmill velocity attained during
the test (4.1±0.4 m/s), indicating a rating of perceived exertion (RPE) of 12.3±1.8
points (Borg scale, range 6-20 points), while the fastest decile of men (n = 32) ran
at 91±3.1 % (corresponding to 5.4±0.2 m/s) of their maximal treadmill speed (5.9±0.2
m/s), indicating a RPE of 16.6±1.1 points. Very similar results were observed in women.
There was a highly significant, positive correlation between running speed eliciting
a blood lactate concentration of 4 mmol/l and RPE when running at this speed, with
r = 0.64 in men and r = 0.55 in women. At the same proportional level of maximal running
velocity, poorly endurance-trained athletes showed a 2-3 mmol/l higher capillary lactate
concentration than well endurance-trained athletes, with both groups indicating the
same RPE. These results suggest that fixed blood lactate concentrations not at all
mean the same exercise intensity for well vs poorly endurance-trained subjects; this
systemic trend should be considered when using blood lactate assessment for individual
exercise counselling.
Key words
Exercise - endurance capacity - maximal running velocity - lactate - rating of perceived
exertion.
