Researchers wanted to know if drinking watermelon juice before exercise could help muscles grow bigger and recover better. They had 42 men do endurance training three times a week for 8 weeks. Half the men drank watermelon juice before exercising, while the other half drank a fake drink with the same calories. The watermelon juice group ended up with slightly bigger chest and leg muscles and felt less sore 24 hours after workouts. However, the juice didn’t help them exercise harder or longer. These results suggest watermelon juice might help with muscle recovery and growth, but scientists need to do more research to be sure.

The Quick Take

  • What they studied: Whether drinking watermelon juice before exercise helps muscles grow bigger, reduces soreness, and improves how hard people can exercise.
  • Who participated: 42 regular men (not athletes) who weren’t used to serious training. They were split into two equal groups of 21 each and exercised three times per week for 8 weeks.
  • Key finding: Men who drank watermelon juice developed slightly thicker chest and leg muscles compared to the control group, and reported less muscle soreness 24 hours after exercise. However, both groups performed equally well during the actual workouts.
  • What it means for you: If you’re doing regular endurance exercise, watermelon juice might help your muscles recover better and grow slightly more, but it won’t make you able to run faster or longer. This is early research, so talk to your doctor before making big changes to your routine.

The Research Details

This was a randomized controlled trial, which is one of the best ways to test if something actually works. The researchers randomly divided 42 non-athlete men into two groups. One group drank 710 milliliters (about 24 ounces) of watermelon juice one hour before each workout, while the other group drank a fake drink with the same number of calories. Both groups did the same endurance exercise program three times per week for 8 weeks.

The study measured three main things: how well people exercised (exercise performance), how sore their muscles felt right after and 24 hours after workouts, and how much their muscles grew. To measure muscle growth, doctors used ultrasound (the same technology used to look at babies before birth) to measure the thickness of two important muscles: the chest muscle and the thigh muscle.

Both groups were told to keep eating the same way they normally did throughout the study. This is important because diet affects muscle growth, so keeping it the same helps researchers know that any differences were from the watermelon juice, not from eating differently.

Using a randomized controlled trial with a placebo (fake drink) is important because it helps prove that results come from the watermelon juice itself, not from people just thinking it will help them. By measuring muscle thickness with ultrasound instead of just asking people if they felt stronger, the researchers got objective, real measurements. Testing both exercise performance and muscle soreness gives a complete picture of what watermelon juice actually does.

This study has several strengths: it used a control group, randomly assigned people to groups, and measured actual muscle thickness with ultrasound rather than relying on people’s opinions. However, the study only included 42 men who weren’t athletes, so results might be different for women, older people, or trained athletes. The study lasted only 8 weeks, so we don’t know if benefits continue longer. The researchers were open about what people were drinking (not blinded), which could have affected results if people expected the watermelon juice to work.

What the Results Show

The watermelon juice group developed noticeably thicker chest muscles compared to the control group. On average, their chest muscles grew about 2 millimeters thicker. Their thigh muscles also grew about 1.7 millimeters thicker. These differences were statistically significant, meaning they were unlikely to happen by chance.

The watermelon juice group also reported less muscle soreness 24 hours after exercise compared to the control group. This is the time when muscle soreness is usually worst. Right after exercise, both groups felt similarly sore, but the watermelon group felt better the next day.

However, there was no difference in exercise performance between the groups. Both groups could do the same amount of exercise and work at the same intensity. The watermelon juice didn’t make people able to run longer, lift more, or exercise harder.

The study didn’t report other major secondary findings, but the fact that muscle soreness decreased 24 hours after exercise is important. This suggests watermelon juice might help with recovery, which is when muscles actually grow and repair themselves. The timing of the soreness reduction (only at 24 hours, not immediately) suggests the juice helps with the recovery process rather than preventing initial muscle damage.

Previous research has suggested that watermelon contains citrulline, a compound that might improve blood flow and help muscles recover. This study supports that idea by showing better recovery and muscle growth. However, most previous studies looked at watermelon’s effects on exercise performance (like running speed), and this study found no improvement there. This suggests watermelon juice might be better for recovery than for immediate performance.

The study only included 42 men who weren’t athletes, so results might be different for women, older adults, or people who already exercise regularly. The study lasted only 8 weeks, so we don’t know if benefits continue or get better over longer periods. The researchers weren’t blinded (they knew who got watermelon juice), which could have affected how they measured results. The study didn’t measure other important things like overall fitness improvements or changes in body composition. Finally, the study was relatively small, so larger studies are needed to confirm these findings.

The Bottom Line

If you do regular endurance exercise (like running or cycling), drinking watermelon juice before workouts may help your muscles grow slightly and feel less sore the next day. However, don’t expect it to make you exercise harder or longer. A reasonable approach would be to drink about 24 ounces of watermelon juice about an hour before exercise. This recommendation has moderate confidence because the study was small and only tested men. More research is needed before making strong claims.

This research is most relevant for non-athlete men doing regular endurance exercise who want to optimize recovery and muscle growth. It may also apply to women and other groups, but the study didn’t test them. People with diabetes or those watching their sugar intake should be cautious, as watermelon juice contains natural sugars. If you have any health conditions or take medications, talk to your doctor before making changes to your diet or exercise routine.

Based on this study, you would need to exercise regularly with watermelon juice for at least 8 weeks to see muscle growth changes. Reduced soreness might happen sooner, possibly within the first few weeks. Don’t expect immediate performance improvements—the study found none even after 8 weeks.

Want to Apply This Research?

  • Track muscle soreness on a scale of 1-10 at 24 hours after each workout. Record this in your app along with the date and type of exercise. After 4-8 weeks, compare your average soreness scores before and after adding watermelon juice to see if you notice a personal difference.
  • Add a reminder in your app to drink 24 ounces of watermelon juice exactly one hour before your scheduled endurance workouts. Log when you drink it and note any changes in how you feel the next day. You could also track your actual workouts to make sure you’re exercising consistently.
  • Create a simple weekly log in your app with columns for: date, type of exercise, whether you drank watermelon juice, and muscle soreness rating 24 hours later. After 8 weeks, review your data to see if there’s a pattern showing less soreness on days when you drank the juice. This personal tracking helps you decide if watermelon juice works for your body specifically.

This research is preliminary and was conducted on a small group of non-athlete men. Results may not apply to women, older adults, athletes, or people with certain health conditions. Watermelon juice contains natural sugars and may not be appropriate for people with diabetes or those managing blood sugar. Always consult with your healthcare provider or registered dietitian before making significant changes to your diet or exercise routine, especially if you have any underlying health conditions or take medications. This information is for educational purposes and should not replace professional medical advice.