Watermelon has genuine exercise-relevant nutrients, particularly the amino acid L-citrulline, natural sugars, and a high water content. But the research on whether eating it before a workout actually improves performance is surprisingly underwhelming. Where watermelon consistently shows up in studies is not in making you stronger or faster during a session, but in easing muscle soreness afterward and keeping you hydrated. That gap between what the nutrients promise on paper and what the body actually does with them before exercise is worth understanding.
What Makes Watermelon Interesting for Exercise
Watermelon is roughly 92 percent water, which already makes it useful around physical activity. Beyond hydration, it contains a meaningful amount of L-citrulline, an amino acid concentrated in the rind and flesh. Once you eat it, your kidneys convert citrulline into L-arginine, which the body then uses to produce nitric oxide. Nitric oxide relaxes blood vessels, and the theory is that more of it circulating before exercise means better blood flow to working muscles, more efficient oxygen delivery, and potentially better performance.
A two-week watermelon juice supplementation study found that plasma citrulline, arginine, and nitrite levels all rose significantly compared to a placebo. Nitrite, a marker of nitric oxide production, roughly doubled in the watermelon group.1PubMed. Two weeks of watermelon juice supplementation improves nitric oxide bioavailability but not endurance exercise performance in humans Watermelon also supplies lycopene, the same red pigment found in tomatoes, which functions as an antioxidant. A randomized trial of daily watermelon juice consumption confirmed that it significantly increased circulating lycopene levels.2PubMed Central. Daily 100% Watermelon Juice Consumption and Vascular Function among Postmenopausal Women: A Randomized Controlled Trial On top of that, a standard serving of watermelon delivers about 11 to 12 grams of carbohydrate, mostly from fructose and glucose, giving your muscles a quick energy source.
The Performance Gap
Here is where the story gets honest. Despite watermelon’s ability to boost nitric oxide markers in the blood, study after study has failed to show that this translates into measurably better exercise performance when taken as a pre-workout. A study testing a single dose of watermelon juice (containing about 1 gram of citrulline) found no significant effect on total repetitions performed, time to exhaustion, VO2 max, or anaerobic threshold compared to a placebo.3PubMed. The effect of l-citrulline and watermelon juice supplementation on anaerobic and aerobic exercise performance The researchers also checked whether taking it one hour versus two hours before exercise mattered. It did not.
Resistance training tells a similar story. When resistance-trained men took watermelon supplements before lifting, there was no meaningful improvement in isometric force production, bench press performance, or blood vessel diameter compared to placebo.4PubMed. Effect of watermelon supplementation on exercise performance, muscle oxygenation, and vessel diameter in resistance-trained men The one bright spot: skeletal muscle oxygenation during exercise did show a modest improvement of about 4 percent, but that did not carry over into any detectable performance gain. The same two-week supplementation study that successfully doubled nitrite levels also found no improvement in endurance exercise performance.1PubMed. Two weeks of watermelon juice supplementation improves nitric oxide bioavailability but not endurance exercise performance in humans
The reason is likely a dose problem. A typical serving of watermelon juice gives you around 1 gram of citrulline. Most studies that have found citrulline supplements improve exercise performance used doses of 6 to 8 grams of pure citrulline, which is roughly six to eight times what you would get from a glass of watermelon juice. A review of the evidence concluded that chronic L-citrulline supplementation at higher doses can improve exercise performance in healthy adults, but acute intake at the levels found in watermelon does not reliably do so.5Current Opinion in Clinical Nutrition & Metabolic Care. Influence of L-citrulline and watermelon supplementation on vascular function and exercise performance
Where Watermelon Actually Helps: Soreness and Recovery
If the performance data is disappointing, the recovery data redeems watermelon considerably. Multiple studies point to reduced muscle soreness when watermelon juice is consumed around exercise. In one trial involving athletes performing high-intensity cycling, both natural and citrulline-enriched watermelon juice reduced recovery heart rate and muscle soreness measured 24 hours after exercise.6PubMed. Watermelon juice: potential functional drink for sore muscle relief in athletes
A randomized controlled trial in non-athlete men doing endurance training found that those consuming about 710 milliliters of watermelon juice an hour before exercise had significantly lower muscle soreness a day later compared to a calorie-matched placebo group. That same study also found something unexpected: the watermelon group showed a significant increase in pectoralis major and rectus femoris muscle thickness, suggesting the juice may support muscle repair and growth during a training program.7PubMed Central. The Effects of Watermelon Juice on Muscle Hypertrophy, Exercise Performance, and Muscle Soreness in Non-Athlete Men Undergoing Endurance Training: A Randomized Controlled Trial Interestingly, exercise performance itself did not differ between the groups in that trial, reinforcing the pattern: watermelon helps with what happens after you train, not necessarily during.
A comparative study pitting watermelon juice against pure L-citrulline supplements for delayed-onset muscle soreness (DOMS) found that both reduced soreness at 12 and 24 hours after eccentric exercise, with no significant difference in effectiveness between the two.8JOSSAE (Journal of Sport Science and Education). Difference Between Watermelon Juice and Pure L-citrulline on Muscle Soreness After Eccentric Exercise: A Comparative Study That is a useful finding because it suggests you do not need an isolated supplement to get the soreness-reducing benefit. The whole juice works just as well, and it comes with hydration, carbohydrates, and antioxidants that a capsule does not provide.
The Antioxidant and Anti-Inflammatory Angle
Intense exercise triggers a spike in oxidative stress and inflammation, which is a normal part of how your body adapts and gets stronger. But when that inflammatory response is excessive or prolonged, it contributes to lingering soreness, fatigue, and slower recovery. A systematic review examining the antioxidant and anti-inflammatory properties of watermelon concluded that its flavonoid content can reduce exercise-induced oxidative stress. The review also found that watermelon’s anti-inflammatory compounds work partly by inhibiting a signaling pathway involved in inflammation and by suppressing pro-inflammatory molecules like TNF-alpha.9Retos. Las propiedades antioxidantes y antiinflamatorias de la sandÃa (Citrullus Lanatus) tienen el potencial de reducir el estrés oxidativo y la inflamación después del ejercicio/actividad fÃsica: Revisión sistemática
This likely explains the consistent soreness reduction seen in trials. It is not just the citrulline doing the work. Lycopene, vitamin C, and other phytochemicals in watermelon contribute to a broader antioxidant package. That said, there is a philosophical wrinkle: some sports scientists argue that aggressively blunting the inflammatory response to exercise could interfere with long-term training adaptations, since your body partly relies on that stress signal to build muscle and improve endurance. The doses of antioxidants in watermelon are modest enough that this is unlikely to be a practical concern for most people, but it is worth knowing the debate exists.
Hydration and Carbohydrate Fueling
One of watermelon’s most straightforward pre-workout benefits is hydration. Starting a workout dehydrated meaningfully hurts performance, and many people show up to train already in a mild fluid deficit. A study comparing watermelon juice to a standard carbohydrate sports drink found that both performed equally well for rehydration and subsequent anaerobic performance in active male adolescents. The researchers noted that because watermelon juice also delivers vitamins and minerals that a simple carbohydrate drink lacks, it may be the better choice.10Journal of Kerman University of Medical Sciences. Effect of Watermelon Juice Compared to Carbohydrate Drinks on Rehydration and Anaerobic Performance in Active Male Adolescents
On the carbohydrate side, watermelon delivers sugar quickly. A study comparing watermelon to a calorie-matched carbohydrate beverage during prolonged cycling found that blood glucose rose by about 30 percent in both groups, with no difference in blood lactate either. The mean carbohydrate intake was around 182 grams across the exercise session in both conditions, and the metabolic response was indistinguishable.11PubMed Central. Comparison of Watermelon and Carbohydrate Beverage on Exercise-Induced Alterations in Systemic Inflammation, Immune Dysfunction, and Plasma Antioxidant Capacity That trial was using watermelon as fuel during exercise rather than purely as a pre-workout snack, but the finding is relevant: watermelon delivers usable carbohydrates at a rate your body handles similarly to a sports drink.
Acute Versus Chronic Intake
A pattern running through the research is that a single pre-workout serving of watermelon rarely moves the needle on performance, but consuming it regularly over days or weeks starts to show benefits. The fatigue-reduction finding in recreational football players, for example, came after seven consecutive days of consuming 500 milliliters of watermelon beverage. That group saw a significant decrease in fatigue index, while the placebo group did not.12Academia.edu. The Effect of Watermelon Beverage Ingestion on Fatigue Index in Young-Male, Recreational Football Players The nitric oxide study similarly required two weeks of daily supplementation before plasma nitrite levels doubled.1PubMed. Two weeks of watermelon juice supplementation improves nitric oxide bioavailability but not endurance exercise performance in humans
The broader review of L-citrulline and watermelon supplementation echoed this: chronic supplementation can increase nitric oxide synthesis, lower blood pressure, and improve skeletal muscle oxygenation, while acute single doses tend to fall short of exercise performance thresholds.5Current Opinion in Clinical Nutrition & Metabolic Care. Influence of L-citrulline and watermelon supplementation on vascular function and exercise performance If you are hoping to grab a slice of watermelon before your session today and feel a noticeable difference in the gym, the evidence says that is unlikely. If you make watermelon a regular part of your diet in the days leading up to training, you have a better shot at experiencing the recovery and fatigue benefits.
Practical Considerations for Timing and Amount
Most of the trials that found soreness-reduction benefits used about 500 to 710 milliliters of watermelon juice, consumed roughly one hour before exercise. That is a lot of liquid. A 710-milliliter serving is nearly three cups, which could leave you feeling sloshy if you are about to do burpees or heavy squats. For solid watermelon, that volume translates to somewhere around three to four cups of cubed fruit. The sugar content also adds up: three cups of watermelon cubes contain roughly 30 grams of sugar, which is fine if you are fueling for an endurance session but might be more than you want before a short, low-intensity workout.
Timing matters for digestion. Watermelon is low in fat and fiber, which means it empties from the stomach quickly. Eating it 30 to 60 minutes before exercise is generally comfortable for most people. If you are doing high-intensity interval training or anything involving a lot of jumping, consider drinking watermelon juice rather than eating whole fruit, simply to reduce the volume sitting in your stomach.
One thing to be aware of: watermelon’s fructose content can cause gastrointestinal distress in some people, especially in larger servings. If you have a sensitive stomach during exercise, start with a smaller amount and see how you respond before committing to a full 700-milliliter pre-workout serving.
Fresh Watermelon Versus Processed Juice
Not all watermelon products deliver the same nutrient profile. Research on pasteurized watermelon juice found that heat treatment degrades some of its key compounds over time. Lycopene content dropped from about 14.7 milligrams per kilogram to roughly 10.1 to 10.5 milligrams per kilogram after pasteurization and 30 days of refrigerated storage. L-citrulline levels similarly fell by about 20 to 23 percent under the same conditions.13Journal of Food Quality. Preservation of Bioactive Compounds and Quality Parameters of Watermelon Juice Enriched with L-Citrulline through Short Thermal Treatment Fresh watermelon or freshly squeezed juice preserves more of the citrulline and lycopene than a shelf-stable bottled product that has been pasteurized and stored for weeks.
Cold-pressed watermelon juices sold commercially vary widely in how much processing they have undergone. If you are buying a bottled product, check whether it is made from concentrate (which involves more heat and may lose more citrulline) versus cold-pressed or high-pressure processed. When in doubt, whole fresh watermelon straight from the cutting board gives you the most intact nutrient profile.
How Watermelon Compares to Other Pre-Workout Foods
Watermelon occupies an unusual niche. It is not a concentrated carbohydrate source like a banana or a handful of dates. It is not a caffeine delivery vehicle. It does not contain creatine or beta-alanine or any of the ingredients found in powdered pre-workout supplements. What it offers is a natural, low-calorie way to hydrate, deliver moderate carbohydrates, and provide a slow-drip citrulline dose that, over time, supports nitric oxide production and post-exercise recovery.
For someone doing a moderate cardio or resistance session and looking for a light, easy-to-digest snack beforehand, watermelon works well. For someone doing a high-performance endurance event or a maximal-effort lifting session, watermelon alone probably does not provide enough concentrated fuel or ergogenic kick to replace a more targeted pre-workout strategy. It is better understood as a useful component of an overall sports nutrition approach rather than a standalone performance booster.
Blood Pressure Effects and Who Should Be Careful
Watermelon extract has been studied for its effects on blood pressure, and the results are relevant for people who exercise while managing cardiovascular issues. One trial in people with elevated blood pressure found that watermelon extract reduced systolic blood pressure from about 138 to 126 mmHg and diastolic pressure from about 79 to 72 mmHg over the study period, though these changes were not significantly different from the placebo group’s trajectory.14PubMed Central. Watermelon extract reduces blood pressure but does not change sympathovagal balance in prehypertensive and hypertensive subjects That suggests watermelon may have a modest blood-pressure-lowering effect, which is generally a good thing for cardiovascular health but could theoretically interact with blood pressure medications. If you already take antihypertensives and plan to consume large amounts of watermelon juice before exercise, it is worth mentioning to your doctor.
Watermelon is also a notable source of potassium. For most healthy people this is a benefit, but individuals with compromised kidney function need to be cautious about potassium intake from any concentrated food source, watermelon included. Large servings of watermelon juice deliver more potassium than casual snacking on a few cubes would, so the amount matters.
The Rind, Where Most Citrulline Lives
An underappreciated detail: the white rind of the watermelon contains substantially more citrulline than the red flesh. Most people throw the rind away, which means they are discarding the part with the highest concentration of the amino acid responsible for watermelon’s exercise-related reputation. Some athletes and supplement companies have started using rind extracts or blending the rind into smoothies to capture more citrulline. The taste is mild and slightly vegetal, making it easy to mask with other fruits. If you are specifically eating watermelon for its citrulline content, tossing the rind means you are leaving a lot of the active ingredient on the plate.
Pickling the rind is a traditional preparation in parts of the American South and East Asia, though the citrulline content of pickled rind has not been well studied. Blending raw rind into a smoothie with the red flesh and some lime juice is probably the simplest way to get more citrulline without resorting to supplements. Whether the additional citrulline from rind consumption would push the total dose high enough to cross the performance threshold seen in pure supplement studies remains an open question that no trial has directly tested.