Young Ju, Ph.D.

A tennis match often lasts ~1 – 2 hours for amateur players and even more than 5 hours for some professionals.  During a match, multiple changes occur in muscles including lowering glycogen (stored energy source), protein, and creatine, and increasing lactic acid. These changes could cause muscle fatigue resulting in a progressive decline in performance.  Although the exact causes of muscular fatigue during tennis play have not been determined, they are multifactorial including muscle protein degradation and muscle damage.  Muscle proteins are constantly turning over (degradation and synthesis). The balance between the rates of synthesis and degradation of muscle proteins determines the amount of protein in muscle.  During a competitive tennis match, the rate of degradation may be greater than the rate of synthesis. 

Researchers have studied effective nutritional recovery strategies for muscle fatigue for decades.  Adequate protein intake may be one of the most important means for tennis players to promote synthesis of muscle protein and muscle recovery.

When and How Much Protein to Take

Protein is one of the macronutrients that provide energy to the body (fat and carbohydrate are the other two).  When digested, food proteins are converted into smaller units called amino acids. These amino acids are broken down in the liver.  Some are transported throughout the body for various bodily functions, including hormone production and regulation and muscle tissue repair/synthesis.  About 20% of protein is stored in your muscular structure.

The Recommended Dietary Allowance (RDA) for protein to meet basic nutritional requirements is 0.8 grams per kilogram of body weight per day (equivalent to 54.4 grams for a 150-pound person). For tennis players at high intensity training and competition, it has been recommended to consume ~1.5 – 1.7 grams of protein per kilogram of body weight per day (102 – 116 g/150-pound player) to maximize muscle protein synthesis (Ranchordas et al., 2013).  Researchers have also shown that there is a 45-minute window after training or competition that is the most efficient time to restore glycogen and protein and repair muscle damage.  During this recovery window, it is recommended to consume 6-20 grams of protein (Kovacs et al., 2009; Phillips and Loon, 2011). 

Foods Containing Protein

It is important to note that getting proteins from protein-rich whole foods should be your priority.  There are a variety of foods containing protein without turning to a protein supplement.

Table 1. Protein Content in Food (USDA) 

Protein Supplements 

If you cannot maintain adequate protein intake from whole foods, you may need to use protein supplements.  Protein is one of the most popular dietary supplements marketed to athletes in the form of powders, bars, and beverages.  Protein powders can be made from whey, casein, egg, soy, pea, hemp, or rice.  You may find different types of protein on the supplement fact panel, such as protein concentrate, protein isolate, and  protein hydrolysate.

• Protein concentrate contains low levels of fat and low levels of carbohydrates.  Depending on how concentrated it is, the protein content ranges from 30 to 90%.

• Protein isolates are further processed to remove all the fat and lactose. Usually protein isolates contain at least 90% protein.

• Protein hydrolysate (also called “predigested”) is a form of protein created to improve absorption in the body.  (Protein hydrolysate is commonly used in medical protein supplements and infant formula.)  The most common source is whey protein concentrate, and the protein content of most products ranges from 20-30 grams per serving.

Potential Adverse Effects

Although ingesting too much protein from food sources is rare, there are risks to consider when using protein supplements.  Consuming recommended doses of protein does not typically cause any adverse effects.  However, consuming very high amounts can cause stomach pains, cramps, reduced appetite, nausea, headache, fatigue, and acne.  Weight gain and a sudden increase in blood sugar have been also

reported due to added sugars and calories in protein supplements.  Some human studies have shown that up to 2.5 – 3.3 grams per kilogram of body weight can be tolerated (Jager et al., 2017). However, long-term safety studies are still required to establish an upper limit for protein supplement consumption. 

These people should avoid high-protein foods or supplements (Karlund et al., 2019):

• People with protein allergy or lactose intolerance should avoid potential food allergens.

• People with irritable bowel syndrome or FODMAP (fermented oligo-, di-, mono-saccharides and polyols) sensitivity may experience bloating and cramping from pea protein or protein powders with added sugar alcohols (used as low-calorie sweeteners).

• People with kidney disease or impaired kidney function as high-protein intake can aggravate kidney dysfunction resulting in kidney damage. 

REFERENCES

Jäger et al. J. International Society of Sports Nutrition Position Stand: protein and exercise. J Int Soc Sports Nutr.  2017 14:20. 

Karlund et al. Protein supplementations and their relation with nutrition, microbiota composition and health: Is more protein always better for sportspeople? Nutrients 2019, 11(4):829.

Kovacs et al. Tennis Recovery: A comprehensive review of the research. USTA 2009.

Phillips and Van Loon. Dietary protein for athletes: from requirements to optimum adaptation. J Sports Sci 2011  29(Suppl 1):S29. 

Ranchordas et al. Nutrition for tennis: practical recommendations. J Sports Sci & Med 2013, 12(2): 211.

Reid M, and Duffield R. The development of fatigue during match-play tennis. Br J Sports Med 2014, 48:i7.

USDA National Nutrient Database for Standard Reference Legacy (2018) Nutrients: Protein https://www.nal.usda.gov/sites/www.nal.usda.gov/files/protein.pdf

People with any other health problems should talk to their healthcare providers about protein intake.  As always, this information is provided for your reference, and you use at your own risk; you should rely on your medical professional for medical advice.