In non-athlete men performing endurance training, daily consumption of 710 mL of watermelon juice is associated with a statistically significant reduction in muscle soreness 24 hours after exercise compared to a calorie-matched placebo, with a mean difference of 0.61 points on a 10-point visual analog scale.

After drinking watermelon juice, a compound called L-citrulline enters the bloodstream and gets turned into arginine in the kidneys. Arginine is then used to make nitric oxide, a molecule that widens blood vessels in the muscles. This allows more blood to flow through, bringing in oxygen and nutrients while flushing out waste products like ammonia and lactate. At the same time, natural antioxidants in the juice prevent nitric oxide from being destroyed by harmful molecules produced during exercise. With better blood flow and less waste buildup, muscle tissue recovers faster and becomes less sore the next day.