Relationship between blood lactate and cortical excitability between taekwondo athletes and non-athletes after hand-grip exercise

Objectives: In taekwondo competitions, fatigue has a large influence on performance. Recent studies have reported that the excitability in the primary hand motor cortex, investigated with transcranial magnetic stimulation (TMS), is enhanced at the end of a maximal exercise and that this improvement correlates with blood lactate. The aim of the present study was to investigate the relationship between blood lactate and cortical excitability in taekwondo athletes and non-athletes. Methods: The excitability of the primary motor cortex was measured before and after fatiguing hand- grip exercise by TMS. Capillary blood lactate was measured at rest (pre-test), at the end (0 min), and at 3 and 10 min after the exercise by using a ‘‘Lactate Pro’’ portable lactate analyzer. Results: Significant differences in cortical excitability between the two groups were found after the exercise (p<0.05). Furthermore, we found a significant relationship between cortical excitability and blood lactate (p < 0.01). Conclusion: The present findings showed changes in the excitability in the athletes group and also in the non-athletes group. However, blood lactate seems to have the greater effect in trained subjects compared to untrained subjects. In fact, it appears that, during extremely intensive exercise in taek- wondo athletes, lactate may delay the onset of fatigue not only by maintaining the excitability of muscle, but also by increasing the excitability of the primary motor cortex more than in non-athletes.