Fighting fatigue: Fortified watermelon juice found to improve exercise performance

14 Sep 2017 --- A recent study from Spain has shown that supplementation with watermelon juice enriched with l-citrulline (3.3g/200mL) and pomegranate ellagitannins (22 mg/200mL) had a beneficial effect on exercise performance in 19 young men.

Watermelon juice naturally contains l-citrulline (0.5g/200mL). L-citrulline is a non-essential amino acid that can reduce the accumulation of lactic acid in the blood and has been shown to allow for higher levels of exercise resistance performance to exhaustion. It is also an important component of the liver urea cycle that is responsible for detoxification of ammonia into urea.

In addition, l-citrulline is a precursor to arginine, an amino acid that can be converted to nitric oxide, which could aid in increasing blood flow and performance during exercise.

Study tests all four treatments
The study was a double-blind, randomized, placebo-controlled, crossover study design so that all subjects received all four treatments: placebo, watermelon juice alone, watermelon with 3.3g/200mL added l-citrulline, and watermelon juice with both 3.3g/200mL l-citrulline and 22mg/200mL pomegranate ellagitannins. A high-intensity exercise test and isometric exercises were performed every seven days to allow sufficient time for washout between exercise tests. A 200mL dose of the various beverage treatments was consumed one hour before exercise testing.

The investigators tested the knee extension peak torque in an isokinetic exercise test after the subjects performed the intensive exercise test and observed an increase in average peak force after the consumption of watermelon juice with added l-citrulline. They measured lower peak torque after participants consumed the watermelon juice plus citrulline and ellagitannins compared to the placebo beverage.

Besides these objective measures of exercise performance, the subjects also rated their perceived exertion and level of muscle soreness up to 48 hours post-exercise. The perceived exertion and muscle soreness following exercise was lower after the beverage treatment containing added citrulline alone and citrulline plus ellagitannins than after consuming the placebo. The findings from this small study are encouraging, but additional studies in women and older subjects are warranted, notes the Fortitech Premixes website, which shared the study results.

Exercise can cause acute muscle damage and subsequent muscle fatigue, as well as muscle soreness that can last several days. High-intensity exercise increases the rate of glycolysis, increases blood levels of lactate and ammonia, the latter being a byproduct of muscle (protein) catabolism that contributes to feelings of fatigue.

Athletes therefore often use various ergogenic aids to address fatigue and enhance exercise performance. Natural juices without added sugar and containing bioactive compounds are of interest to the juice industry as possible ergogenic aids, the Fortitech Premixes website reports.

“Consumption of watermelon juice enriched in l-citrulline and pomegranate ellagitannins enhanced metabolism during physical exercise” is published in the Journal of Agricultural and Food Chemistry.