The Effects of high-intensity Resistance- Endurance Training on Physical Fitness, Levels of serum Cortisol, Testosterone, and insulin-like growth factor1 (IGF1) among Adolescent Taekwondo players

Introduction: Strength and endurance training has experienced a surge in popularity in recent years and is currently one of the most commonly practiced training methods. This study investigated the effects of high-intensity resistance, and endurance training on physical fitness and levels of serum cortisol, testosterone, and insulin-like growth factor1 (IGF1) among adolescent athletes’ taekwondo players. Material & Methods: This quasi-experimental study was based on the pre and post-test design with a control group. The first group engaged in moderate-intensity resistance endurance training along with regular taekwondo training (CG). CG performed a total of 95 minutes of training, including warm-up, cool-down, technical and tactical exercises, 50 minutes of moderate-intensity resistance (60-70% of one repetition maximum; 1RM), and endurance (60-70% of target heart rate; THR) training. During this time, the experimental group (EG) performed a total of 80 minutes of the same training, except that they performed high-intensity resistance (70-80% of 1RM) and endurance (70-80% of THR) training for 35 minutes. Participants included 20 male taekwondo players who were randomly assigned to two equal EG and CG groups with more than two years of training experience. They were evaluated for age, height, weight, and some physical fitness parameters such as aerobic capacity (shuttle run test) and anaerobic capacity (RAST test). CG performed conventional moderate-intensity strength and endurance exercises; the EG performed these exercises at high-intensity training for 80 minutes. The variables were measured before and after 8 weeks of training. Moreover, 10 ml of blood was taken from the arm vein of participants both before and after the study to measure the levels of cortisol, testosterone, and IgF1. Results: Results showed a significant increase in the cortisol level and anaerobic capacity in both CG and EG (p<0.05). In addition, the resting metabolic rate (RMR) increased in the EG, and cortisol level decreased in the CG (p<0.05), but aerobic capacity was promot in both groups (p<0.05). In the comparison between groups, only anaerobic capacity increased significantly in the experimental group, and no significant differences were observed in other variables. Conclusion: Considering the positive effects of high-intensity aerobic and resistance training on both aerobic and anaerobic power, it is recommended that taekwondo coaches incorporate these exercises into their athletes' training programs. However, further studies are needed to confirm the effects of these exercises on hormonal and bioenergetic changes in the body. The findings underscore the importance of tailored training regimens that consider individual athlete needs and the specific demands of taekwondo.