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Improving Tennis Stamina Through Electrolyte Supplementation

tennis and electrolytes hydration

In the recent standoff between Novak Djokovic and Andy Murray during the 2015 Miami Open, stamina played a huge role in the ultimate success of Djokovic. As the Associated Press reported:

“Djokovic earned his fifth Key Biscayne title Sunday, beating Andy Murray for the seventh consecutive time by showing superior stamina in the subtropical heat to win the Miami Open final 7-6 (3), 4-6, 6-0. Murray broke in the final game of the second set to even the match, but fatigue then became a factor on a sunny, humid, 80-degree afternoon.”

The news outlet was quick to attribute the win to “superior stamina,” but it does not address the underlying cause for why Djokovic was able to maintain physical performance beyond Murray enough to dominate in the last set. Was it mental will? Likely not, as both men are in the top of their field. Physical conditioning? Maybe, but also unlikely for the same reasons.

This leads to the broader question of whether or how much control we have over our physical performance. If we turn to science, we see that physical conditioning is important, but equally important is nutrition. In this blog post, Part 2 (Here’s Part 1!) of our series in how SaltStick can help tennis players and coaches perform to their peak potential, we’ll examine nutritional causes — particularly the role of electrolytes — for improved physical stamina.

Salt and endurance:

What are electrolytes for? Electrolytes play a variety of roles in the human body, from regulating blood volume to assisting with nutrient absorption. Because of electrolytes’ role in helping muscles contract and release, low electrolyte levels are often thought to contribute to cramping.

Narrowing our focus to endurance, it is important to remind ourselves that endurance sports are essentially muscle contractions (the pull of a swim, the stroke of a pedal, the step of a run, etc.) repeated many, many, many times. Each contraction requires the use of electrolytes, and each contraction produces heat, which raises core body temperature. In effort to cool itself, the sweat glands release a mixture of water and electrolytes (mostly sodium) to rid itself of excess heat.

Lastly, during exercise, the body is burning calories as energy. The longer the duration of the activity, the greater the fluid, caloric and electrolyte loss, and therefore the greater the importance to follow some strategy to replace components in all three categories. This is why tennis coaches tell their players to drink sports drinks and eat bananas during practice and matches.

What happens when your body runs low on calories, water or electrolytes? Put simply: bad things. Because your body needs food, water and salt to perform, you will be forced to stop or slow down when you run low in one of these categories. Too few calories? You’ll run short on glucose, which is the “energy” for your muscles, and you’ll be forced to slow down or stop to allow your body to shift to burning fat (via conversion to glycogen). Too little water? You’ll get dehydrated, and again be forced to slow down or stop. Low electrolytes? You’ll run the risk of an even more dangerous scenario than dehydration — hyponatremia, which happens when your water levels are too high and salt levels are too low. It usually results from some form of over-zealous “water-only” hydration plan (such as sports drinks with very low levels of salt or — worse — plain water), and it will likely be accompanied by confusion, irritability, headaches that won’t go away, nausea or extreme weakness. If you display any of these symptoms, it’s critical to take immediate steps to restore the proper ratio of electrolytes in the body, and in severe cases, medical attention.

What does all this mean? Essentially, if you’re running low on electrolytes, your performance is going to suffer. Taking steps to replace all of your electrolytes — sodium, potassium, magnesium, calcium and chloride — is an important step to getting the most out of your body on match day.

Are there any studies that back this up?

Glad you asked! We recently published a blog post about a study in Spain that examined the effects of electrolyte supplementation on endurance performance. Check out the original blog post for greater detail, but a summary is below:

The study: Researchers at UCJC divided 26 medium-distance triathletes into two groups. The first group completed a half-Ironman race (1.2 mile/1.9k swim, 56 mile/90k bike, and 13.1 mile/21.1k run) consuming sports drink as they usually would, but also consuming SaltStick Caps in order to replace sodium lost through sweat. The second group completed the same distance while consuming sports drink as they usually would, but they received a placebo capsule with no extra sodium. Researchers were aiming to replace about 70 percent of sodium in the first group, but only about 20 percent in the second group, the sole difference due to the electrolyte capsules.

When the triathletes completed the race, researchers tallied up finishing times and found that the triathletes who consumed the sodium tablets finished in an average of 26 minutes (8%) faster! The increase in speed usually came from improved cycling and running times, which come later in the race after electrolyte levels begin to decline.

Key takeaways: 

  • Consuming sports drinks isn’t enough: Most people’s sweat contains sodium at a concentration of 40-60 mEq/L, and in order to stay hydrated, an athlete should replace salt and water and a similar concentration. However, many sports drinks are only concentrated at a 20 mEq/L level (increasing sodium beyond this level results in a less pleasant taste, closer to sea water). What does that mean? It means supplementing with a sports drink may only replenish half of the necessary salts. And as we wrote earlier, low electrolyte levels can hurt performance.
  • Additional electrolyte supplementation had a measured, statistically significant improvement on performance: The 26 athletes were matched for age, anthropometric data, and training status, and randomly placed into the two groups, reducing the chance for measurement error.

How we fit in:

What’s in SaltStick Caps? While the researchers at UCJC focused their study on the effects of sodium, an athlete’s sweat contains several other electrolytes, which are just as important for performance. Replacing the full spectrum will have the most positive effects on boosting endurance.

The average person loses electrolytes in a ratio of 220 Sodium to 63 Potassium to 16 Calcium to 8 Magnesium. That’s why each SaltStick Capsule contains these four electrolytes in the same concentration, to provide your body with the entire range of electrolytes it needs.

We’re not shy about the ingredients in SaltStick. Feel free to check them out here

How can I use SaltStick to improve my tennis performance? We provide a good overview of how your sweat rate plays into your nutrition needs on our website here (“Why should I care about electrolyte loss? Give me a brief summary!”), but essentially, light sweaters or smaller individuals should consider 1 SaltStick Cap per hour. Heavy sweaters, larger individuals, or those in hotter conditions should consider 2-3 SaltStick Caps per hour. The best strategy for success is to practice your nutrition strategy during training so you can optimize for what works for you, and then execute that during racing. We provide a complete suggested usage guide here: Training with SaltStick Capsules.


Were low electrolyte levels ultimately the cause of Andy Murray’s loss? Without being on the scene, it’s impossible to say. Both Murray and Djokovic have told media multiple times that they rely heavily on electrolyte supplementation. However, changes in temperature, humidity, and even diet can affect a person’s sweat rate. Perhaps Murray’s nutrition plan for the day was simply not enough.

It’s entirely possible the loss was due to something unrelated to nutrition, but the match between Murray and Djokovic serves to illustrate that mental and physical stamina alone do not always determine a tennis player’s success. By incorporating the most ideal nutrition plan — which includes full electrolyte supplementation — tennis players will have the best chances for success on match day.