The Effects of Watermelon Juice on Muscle Hypertrophy, Exercise Performance, and Muscle Soreness in Non-Athlete Men Undergoing Endurance Training: A Randomized Controlled Trial.

In the current study, we aimed to assess the impact of watermelon juice as a functional drink on muscle soreness, exercise performance, and muscle hypertrophy. This open-labeled randomized controlled trial was conducted on 42 non-athlete men for 8 weeks. The participants were randomized into two equal groups: the intervention group received 710 mL of watermelon juice, and the control group received a calorie-matched placebo 1 h before exercise. Also, both groups received an endurance exercise plan 3 days a week and were recommended to maintain their dietary routines throughout the study period. At the end of the first week, exercise performance was evaluated, and participants were asked to complete the muscle soreness chart immediately and 24 h after the exercise. Finally, muscle hypertrophy, including the thickness of the pectoralis major and rectus femoris muscles, was measured by ultrasound at the end of the study. No significant differences were observed in exercise performance between groups. However, the intervention group showed a significant increase in the thickness of the pectoralis major (MD: 2.00, 95% confidence interval: 0.87, 3.13) and rectus femoris (MD: 1.70, 95% confidence interval: 0.72, 1.68) muscles and reported lower muscle soreness 24 h post-exercise compared to the control group (p = 0.045). In conclusion, watermelon juice may benefit individuals engaged in regular exercise by optimizing muscle repair and hypertrophic responses. Further research is warranted to confirm its effects on exercise performance across diverse conditions. Trial Registration: This trial was registered on the Iranian Registry of Clinical Trials (IRCT) under registration number IRCT20191105045340N1 on 15/12/2019 (https://irct.behdasht.gov.ir/).