This is a controlled, randomized, and cross-over investigation with 40-week duration. The participants were male young adults with previous experience with RT for testing the effect of long-term RT with different volumes on HRV. This study was conducted in healthy participants in order to investigate the effects of resistance training on HRV without pathological influences. They underwent to a 40-week intervention divided in three RT segments (8 weeks each) and two washouts (8 weeks each) according Figure 1. The intervention order was randomized and counterbalanced. Thus, participants performed 1, 3 or 5 sets of the same exercises with equalized intensity (loading zones) and rest (Table 1) for 8 weeks following 8 weeks of washout between each experimental condition (1 vs. 3 vs. 5 sets).10 repetition maximum (10-RM) test was performed for defining training intensity\u00a0that was adjusted weekly (increase\/decrease of 2-5% and 5-10% for upper and lower limbs, respectively) as recommended by Ribeiro et al. (2016). In case the participant performed more than 10 repetitions in two sessions, load (kg) was increased in the next week, whereas whether the participant was not able to perform 10-RM the load was decreased in the next week.\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 HRV was assessed by cardiac monitoring 72h before (pre) and after (post) each experimental RT condition (1 vs. 3 vs. 5 sets). Moreover, the participants were instructed to not performing any physical exercise 48h previously HRV baseline evaluation.