Aim: 

The accumulation of lactate in the blood after an high-intensity exercise is associated to an increase of lactate extractions by the brain. However, no information has been yet provided about the influences of blood lactate levels on cognitive performances and, in particular, on attention. The aim of the present study was to examine the association of high blood lactate levels, induced with a maximal cycling, with two different attentional tasks.

Methods: 

The study was carried out on 24 male athletes from the Track and Field Team of the University. Eighteen subjects performed a maximal cycling test on a mechanically braked cycloergometer. Before the exercise as well as 5 and 10 minutes after the exhaustion, blood lactate was measured and intensity as well as selectivity of attention of each subject were evaluated. Six subjects received an intravenous infusion of a 2 mEq/ml lactate solution in absence of any motor activity; also in this case, blood lactate was measured and intensity as well as selectivity of attention of each subject were evaluated before the injection as well as 5 and 10 minutes after the infusion.

Results: 

Blood lactate increased from a mean value of 1.5 mmol/l (0.39) before the exercise to a mean value of 10.1 mmol/l (2.61) 5 min after its end and decreased to a mean value of 2.87 mmol/l (0.66) 10 min after its end. Reaction time (RT) values increased after the exercise, from a mean value of 270.23 ms (14.51) before the exercise up to a mean value of 298.09 ms (21.67) 5 min after its end; RT decreased to a mean value of 277.6 ms (14.80) 10 min after its end. Concerning the divided attention task, we observed a mean number of wrong performances of 0.9 (1.13) before the exercise, of 2.3 errors (1.08) 5 min after its end, and of 1.3 errors (0.96) 10 min after its end. Therefore, it was observed an inverse relation between scores in both aspects of attention and blood lactate levels.

Conclusion: 

On this basis, we believe that the exercise-induced increase of blood lactate could be per se capable of altering both selectivity and intensity of attentional mechanisms in the frontal cortex.