Why Endurance Athletes Need Protein Too

By Ashley Sobel, RD, CDN

Protein is often thought of as a key macronutrient for athletes focusing on strength training, however, it should definitely not be overlooked for endurance athletes. In fact, protein is equally as important for endurance athletes as it is for strength training athletes. In addition to carbohydrates, endurance athletes require adequate protein for optimal performance. Here’s why:

Protein repairs muscle tissues in endurance athletes

While bodybuilders require protein to increase and repair muscle tissue, endurance athletes need protein to repair muscle tissue that undergoes constant breakdown from day-to-day training. Whether biking, swimming, or cross-country skiing long distances, for example, athletes expend more energy than the average individual, meaning they require additional nutrition to recover and repair their bodies after increased physical demand. If endurance athletes fail to consume adequate protein, there is an impaired ability for the body to build and repair muscles. 

During endurance training, approximately 2-6% of energy is derived from the oxidation of amino acids.  Endurance exercise results in increased oxidation of branched chain amino acids (BCAAs). In fact, 18 of the 20 amino acids can be used to produce glucose as an energy source. 

After about 90 minutes of endurance training, an athlete’s carbohydrate, or glycogen stores, become nearly depleted. When the glycogen stores are used up, muscle protein can be broken down into amino acids. These amino acids can then be converted to glucose for energy through a process called gluconeogenesis.  

When these protein stores are tapped into during endurance training, increased muscle loss occurs, resulting in an increased need for dietary protein.  To meet protein needs, endurance athletes require about 1.2-1.4 grams of protein per kilogram of body weight (1). Consuming high-quality protein – one with all 9 essential amino acids – is necessary to aid in the repair of damaged muscle tissue and to stimulate muscle protein synthesis. 

The goal of endurance athletes to be to maintain a positive protein balance, meaning they must meet the protein requirements for baseline needs, plus for the synthesis of new muscle tissue. Muscle growth can only occur if muscle protein synthesis exceeds muscle protein breakdown. For athletes to meet their increased needs, protein supplements are often consumed and provide an efficient and simple way to consume protein.   

Protein intake optimizes glycogen storage

Endurance athletes like cyclists rely heavily on their glycogen, or carbohydrate stores, to sustain prolonged physical activity. Once consumed, carbohydrates are broken down to glucose, and then either utilized for energy or stored as glycogen as a “savings bank” of fuel. High quality protein plays a key role in helping the body optimize its storage of muscle glycogen. To optimize glycogen storage and protein utilization after a workout, it is best to aim for 20-30g of protein within 30-60 min post-workout. In addition to consuming protein, athletes should also consume carbohydrates. Studies suggest that it’s best to consume 4g of carbohydrates for every 1g of protein (2, 3).  

For athletes aiming to limit their carbohydrate intake however, adequate protein intake may even play more of a vital role. In fact, studies show that in cases of suboptimal post-exercise carbohydrate intake, adding dietary protein improves glycogen synthesis and reduces muscle damage (4). 

Protein improves performance for endurance athletes  

Protein is not only important for muscle recovery and enhancing glycogen synthesis, but it can even enhance performance. One way that protein improves endurance performance is by promoting hemoglobin synthesis, which is a body protein that delivers oxygen to muscles. Muscles require a consistent oxygen supply throughout endurance training to fuel continuous exercise, and an impairment in oxygen supply would therefore impede performance. 

What’s more, if athletes under-consume protein, the body may rely on muscle stores to obtain the necessary amino acids for proper hormone function and enzyme development, which if altered, can prevent an athlete from performing optimally.  

Protein also helps increase VO2 max, which is critical for endurance athletes to improve speed and endurance. The VO2 max is the maximal oxygen uptake that can be processed during exercise for, and is a measure of aerobic capacity. Research suggests that protein supplementation allowed for an increase in VO2max in endurance athletes (5). 

While protein supplementation should not replace a healthy, balanced nutritional plan, it can be a great addition to a healthy meal plan to help meet the increased needs of endurance athletes. Please view the recipe below for a great protein-rich snack for runners or other endurance athletes.

Protein power ball recipe (makes about 20)

• 4 scoops of protein powder 
• 1 cup rolled oats
• ½ cup natural peanut butter or almond butter
• ⅓ cup honey
• ¼ cup chopped dark chocolate (or dried cranberries/raisins)
• 2 tablespoons ground flax seeds
• 2 tablespoons chia seeds
• 4 scoops of protein powder 

Directions:

1. Combine all ingredients in a mixing bowl – cover and refrigerate for 30 minutes
2. Arrange batter into 1-inch balls, place on a plate or baking sheet and chill for additional 30 minutes
3. Enjoy 2-3 protein bites before or after a workout
4. Store in refrigerator, enjoy for up to 2 weeks.