We studied, in 15 healthy young male athletes, whether an aerobic exercise, carried out at two different submaximal intensities, is capable to influence attentional processes. In particular we measured blood levels of lactate and glucose with the purpose to evaluate possible correlation between their blood values and attention after a steady 30 min steady-state test performed at 60% and at 80% of maximal oxygen consumption (VO_2max). We analyzed either intensity of attention, by using a typical reaction time paradigm, and selectivity of attention, by using a parallel double task of both visual and auditory recognition that allows to measure errors, omissions and execution time. Five measurements were carried out: before the 30 min exercise, after 10 and 20 min from its beginning, at its end and, finally, 10 min after the conclusion.

We observed that during the exercise, there is an increase of blood lactate, whereas the blood glucose remains unmodified, and that a significant worsening of attentional processes is detectable only at 80% of VO_2max, when the blood lactate overcomes a concentration of 4 mmol/l.

Since we observed that a large increase of blood lactate is associated with an improvement of excitability of the primary motor cortex, we conclude that, during an intense exercise, in the frontal cortex the lactate could carry out a protective role against fatigue, by favoring the activity of primary motor cortex, albeit at the expense of attentional processes.