The effects of low-intensity eccentric quasi-isometric training with blood flow restriction on serum levels of testosterone and cortisol, and on muscular hypertrophy and power in male athletes

Background and Purpose: Achieving high efficiency in athletic training and maximizing muscular output 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 (EQI) training with blood flow restriction (BFR) on serum levels of testosterone and cortisol, and on muscular hypertrophy and power in male athletes.
Materials and Methods: Thirty-six young male athletes were selected and randomly divided into three groups including EQI, the low-intensity EQI+BFR (EQI + BFR), and the control (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 repetitions at an intensity of 60-85% of one repetition maximum (1RM) and a duration under tension of 15-90 seconds per repetition for 5 lower and upper body exercises, and the EQI + BFR group performed the same exercise protocol at an intensity range of 20-35% of 1RM and with BFR. 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 using human ELISA kits. Upper and lower body hypertrophy was measured anthropometrically. Lower body power was also assessed using a vertical jump test. Two-way ANOVA and Bonferroni’s post-hoc test were used for between-group comparisons and paired t-test was used to examine within-group changes.
Results: A significant time × group interaction was observed after six weeks of both EQI and EQI + BFR training for serum levels of testosterone (p=0.014), cortisol (p=0.007), testosterone to cortisol ratio (p=0.005), thigh circumference (p=0.001), arm circumference (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=0.03 and p=0.02, respectively), testosterone to cortisol ratio (p= 0.023 and p=0.007, respectively), arm circumference (p= 0.011 and p=0.001, respectively), and thigh circumference (p= 0.001 and p=0.002, respectively), compared to the control group. The EQI + BFR group showed a significant decrease in cortisol in comparison to the control group (p=0.005), and the EQI group revealed a significant increase in peak (p=0.007) and average leg power (p=0.007) compared to the control group. However, 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 circumferences similarly. However, the role of EQI+BFR was more prominent in reducing cortisol level and high-intensity EQI in improving lower body power. It seems that low-intensity EQI training with BFR can be used interchangeably with high-intensity EQI training.