Effects of High-Intensity Resistance Training on Physical Fitness, Hormonal and Antioxidant Factors: A Randomized Controlled Study Conducted on Young Adult Male Soccer Players

SIMPLE SUMMARY: We aimed to analyze the effects of high-intensity resistance training (HIRT) on physical fitness and hormonal and antioxidant factors of adult young male soccer players. We have compared an 8-week intervention using HIRT period with a control group that only performed regular technical/tactical sessions. The soccer players were assessed before and after the intervention for their physical fitness, and hormonal and antioxidant factors. We have found that using HIRT for 8 weeks, with three sessions a week, results in significant improvements in aerobic capacity, sprint at short (10 m) and medium (20 and 30 m) distances, repeated sprint ability, and change-of-direction. This suggests that HIRT combined with regular field-based practice can provide an additional benefit to physical fitness development. Additionally, the group enrolled on HIRT also exhibited significantly decreased levels of cortisol and malondialdehyde, whereas it exhibited significantly increased growth hormone, testosterone, dis-mutase, and glutathione. The results suggest that HIRT can be an interesting approach for improving physical fitness and adjusting the hormonal and antioxidant levels of adult male soccer players. ABSTRACT: Purpose: The aim of this study was to test the effects of high-intensity resistance training (HIRT) intervention on the physical fitness, hormonal and antioxidant factors of adult male soccer players. Methods: A randomized controlled study design was implemented. Eighteen soccer players (age: 20.3 ± 0.66 years; stature: 174.0 ± 6.01 cm; body mass: 69.1 ± 6.4 kg; body mass index: 22.8 ± 1.6 kg/m(2)) voluntarily participated in this study. Players were assessed before and after an intervention lasting 8 weeks, with three training sessions a week. Assessments of physical fitness included the Yo-Yo intermittent recovery test level 1 (YYIRT1), 10-, 20-, and 30 m sprint time (ST), running-based anaerobic sprint test (RAST) and change-of-direction time (COD). Hormonal tests included cortisol, testosterone and growth hormone (GH), whereas the antioxidant assessment included superoxide dismutase (SOD), malondialdehyde (MDA) and glutathione (GSH). Results: Between-group analysis revealed no significant differences at baseline, whereas it revealed that HIRT presented significant better results than the control group on YYIRT (p = 0.032), 10 m ST (p = 0.041), 20 m ST (p = 0.040), 30 m ST (p = 0.044), RAST (p = 0.013), and COD (p = 0.031) after the intervention period. The within group analysis revealed that the HIRT group significantly improved the YYIRT1 (p < 0.001), VO2max (p < 0.001), 10 m ST (p < 0.001), 20 m ST (p = 0.006), 30 m ST (p < 0.001), RAST (p < 0.001) and COD (p < 0.001). Moreover, HIRT group significantly reduced the cortisol (p < 0.001) and MDA (p = 0.021), whereas it significantly increased the GH (p < 0.001), testosterone (p < 0.001), SOD (p = 0.009) and GSH (p = 0.005). Conclusions: The HIRT is effective for improving physical fitness, revealing significant better adaptations than controls. Moreover, hormonal and antioxidant adaptations are also confirmed after HIRT intervention.