Substantial influence of level of endurance capacity on the association ofperceived exertion with blood lactate accumulation

Capillary blood lactate assessment is increasingly used by well-trained run ners to monitor the intensity of endurance exercise. In order to examine th e known association of exercise intensity with blood lactate accumulation a lso in less trained subjects, we analysed data from a standardized incremen tal maximal test on the treadmill of 319 men (age 22.9 +/- 5.5 years, [mean s +/- S.D.]) and 145 women (22.7 +/- 4.5 years) characterized by a wide var iation in endurance capacity. Results showed that the running velocity elic iting a blood lactate concentration of 4 mmol/l did not correspond to the s ame exercise intensity in well endurance-trained vs poorly endurance-traine d subjects. At 4 mmol/l blood lactate, the slowest decile of men (i.e. 32 o ut of 319) ran at 71 +/- 4.7% (corresponding to 2.9 +/- 0.3 mis) of their m aximal treadmill velocity attained during the test (4.1 +/- 0.4 mis), indic ating a rating of perceived exertion (RPE) of 12.3 +/- 1.8 points (Borg sca le, range 6-20 points), while the Fastest decile of men (n = 32) ran at 91 +/- 3.1 % (corresponding to 5.4 +/- 0.2 mis) of their maximal treadmill spe ed (5.9 +/- 0.2 mis), indicating a RPE of 16.6 +/- 1.1 points. Very similar results were observed in women. There was a highly significant, positive c orrelation 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 lact ate concentration than well endurance-trained athletes, with both groups in dicating the same RPE. These results suggest that fixed blood lactate conce ntrations not at all mean the same exercise intensity for well vs poorly en durance-trained subjects; this systemic trend should be considered when usi ng blood lactate assessment for individual exercise counselling.