The Effects of Low-Intensity Eccentric Quasi-Isometric Training with Blood Flow Restriction on Serum levels of Testosterone, Cortisol, Muscular Hypertrophy, and Power in Male Athletes

Objective: Achieving high efficiency in athletic training and maximizing muscular output relative to the effort expended is of critical importance to both coaches and athletes. Therefore, the purpose of this study was to investigate the effects of six weeks of low-intensity eccentric quasi-isometric training (EQI) with blood flow restriction (BFR) on serum levels of testosterone, cortisol, muscular hypertrophy, and power in male athletes.
Methods: Thirty-six young male athletes were selected and randomly divided into three groups, including EQI group, the low-intensity EQI+BFR group (EQI + BFR), and the control group (CON). The training groups performed EQI resistance training in addition to their routine training for 6 weeks, 2 sessions per week. The EQI group performed weight training using the eccentric quasi-isometric method, 3-4 repetions with an intensity range of 60-85% of one repetition maximum (1RM) and a duration under tension of 15-90 seconds per repition for 5 lower and upper body exercises, and the EQI + BFR group performed weight training using the eccentric quasi-isometric method, 3-4 repetions with an intensity range of 20-35% of 1RM and a duration under tension of 15-90 seconds per repitions for 5 lower and upper body exercises. The control group performed their routine exercise activities. Fasting blood samples were taken 48 hours before the first training session and 48 hours after the last training session. Serum testosterone and cortisol levels were measured with human ELISA kits. Upper and lower body hypertrophy was measured anthropometrically. Foot grip strength was also assessed based on vertical jump. Two-way ANOVA with dummy measurements and Bonferroni post hoc test were used to analyze the data, and paired t-test was used to examine within-group changes.
Result: a significant time in group interaction observed after six weeks of both EQI and EQI + BFR training on serum levels of testosterone (P=0.014), cortisol (P=0.007), testosterone to cortisol ratio (P=0.005), thigh hypertrophy (P=0.001), arm hypertrophy (P=0.001), mean (P=0.009) and peak leg power (P=0.009). Between-group results showed that both EQI and EQI + BFR training significantly increased testosterone levels (P values 0.03 and 0.02, respectively), testosterone to cortisol ratio (P values 0.023 and 0.007, respectively), arm muscle hypertrophy (P values 0.011 and 0.001, respectively), and thigh hypertrophy (P values 0.001 and 0.002, respectively), compared to the control group. The EQI + BFR group had a significant decrease in cortisol relative to the control group (P = 0.005), and the EQI group had a significant increase in peak (P = 0.007) and average leg power (P = 0.007) compared to the control group. There was no significant difference between the EQI and EQI + BFR training groups in all variables (P > 0.05).
Conclusion: The results of the present study showed that both high-intensity EQI and low-intensity EQI+BFR training can improve testosterone serum levels, testosterone to cortisol ratio, arm and thigh hypertrophy, and there was no difference between the two training methods. However, the role of EQI+BFR was more prominent in reducing cortisol level and high-intensity EQI in improving leg muscle power. It seems that performing low-intensity EQI training with BFR can replace EQI training.