Cardiac autonomic responses and number of repetitions maximum after LED irradiation in the ipsilateral and contralateral lower limb

The aim of this study was to verify the maximum number of repetitions, fatigue index, blood lactate concentration ([Lac]), and cardiac autonomic responses after LED irradiation (LEDI) in the ipsilateral and contralateral limb. Twelve male subjects (22.0 ± 3.86 years; weight 82.94 ± 12.58 kg; height 1.77 ± 0.05 m), physically active, took part in this study. The subjects underwent a one repetition maximum (1RM) test and performed four randomly experimental sessions in the horizontal leg press exercise, which consisted in four sets of maximum repetitions at 80% of 1RM. The subjects performed two experimental sessions applying LED active or placebo on ipsilateral limb and two experimental sessions applying LED active or placebo on contralateral limb prior exercise and in the interval of sets on quadriceps and hamstrings muscles. A number of repetitions and fatigue index were verified. [Lac] and heart rate variability (HRV) were collected during post-exercise recovery and analyzed. It was observed that active LEDI promoted an increase in maximal number of repetitions (LEDI = 44.4 ± 9.0 vs placebo = 39.9 ± 11.4; p 0.05). The LEDI improves performance only in the ipsilateral application, but there were no differences on [Lac] and cardiac autonomic responses after exercise for both the applications.