Why Protein for Endurance Athletes

by Eric Bockelman, Dietitian

Why Protein for Endurance AthletesWhether you are a swimmer, cyclist, or runner, endurance- and cardio-oriented athletes typically fuel their bodies with carbs and skip over one of the most important building blocks in an athlete’s diet: protein. Whether you are a bodybuilder or a marathoner, it is important to integrate adequate amounts of amino acids/protein into your diet. These nutrients are necessary not only for muscle formation but for muscle repair.

For the well fueled athlete, after approximately 60–90 minutes of cardiovascular activity, our stores of muscle glycogen—the amount carbs we can store in our body—are fully depleted. Once this has occurred, our body looks to other sources to balance blood sugar levels. This is a process known as gluconeogenesis, or in plain English: the creation of carbohydrates or energy from non-carbohydrate sources. Basically because your excess/storage quantities of glycogen are gone, your body breaks down muscles to fuel your activities. As you can imagine, when muscle is broken down there can be notable muscle fatigue. Additionally, low quantities of dietary protein can lead to longer recovery periods and significant muscle weakness, which can seriously compromise your performance.

Proteins are the building blocks for your muscles. When these nutrients are not present in adequate quantities in the diet, the potential for increased fatigue, injury, and even sport related anemia are greatly increased.

Protein Quantity, Quality, and Timing

Now that we have illustrated the importance of the structural building blocks, let's note that it is not only the quantity that you are consuming, but the quality and timing of consumption, that are important.

Quality in this context is referring to the macronutrient composition of the protein food items, specifically the fat content. The amount of fat that you can metabolize can be increased based on your own specific ability to metabolize/burn fat. The timing of protein consumption following a workout that can help optimize muscle tissue repair, so getting these structural building blocks into your body in a timely matter following exercise is very important.

If you are getting into the 60–90 minute range for your workouts, then post-workout protein supplementation is necessary to promote active recovery. Most of us have heard of this magical 30-minute window following workouts that we need to get protein on board. This is simply a guideline based on your body’s ability to optimize utilization of proteins after a hard workout. Please note that good sources of clean protein need to be paired with carbohydrates to synthesize or process proteins properly. Carbs help provide the vehicle to better use proteins.

For the vast majority of you out there, if you are not exceeding this hour mark in your workouts, then supplementing protein directly following a workout is not imperative. Simply consuming a balanced diet throughout the day should supply you with adequate protein to facilitate muscle repair.

So the simple question is, how much protein should I be taking in? A good frame of reference for the average American is approximately 1 to 1.2 grams of protein per kilogram of body weight.

So if Jo/e Athlete weighs 150 pounds, her/his protein needs will be as follows.
150 lbs. ÷ 2.2 (conversion factor for lbs to kg) = about 68 kg
1 g × 68 = 68 g
1.2 g × 68 = 81 g
So, 68–81 g protein needed every day

Chocolate milk is a great recovery drinkOnly about 10–20 g of protein would be required following a workout along with about 30 g of carbohydrates for the average athlete. A great way to accomplish this is by drinking chocolate milk. It is almost the perfect paring of carbs to protein. Now that this product has become so widely used by endurance athletes, it is very easy to find chocolate milk in small portions at your local grocery store. So to prevent muscle fatigue and optimize the quality of your next workout, be sure to supplement your diet with adequate clean protein.

The last point I feel it is important to make is that excessive consumption of protein can and will lead to weight gain. So eating good low-fat sources of protein is ideal when selecting your post workout recovery. A common misconception by endurance athletes is that protein in any quantity will make you big. It is important to note that over-consumption of any nutrient will have negative effects.

Using protein properly in the diet is an integral part of your prolonged health, fitness, and performance as an endurance athlete. Please remember everything in your diet needs to be in moderation. There are no bad foods only bad portion sizes, so find what works best for you.

Protein Smoothie Recipe

Protein smoothie ingredientsHere is a great protein shake recipe that you can integrate into your diet today. Please feel free to alter this recipe to better suit your specific caloric and nutrient needs.

Protein Smoothie for Endurance Athletes


  • 1 banana
  • 3–5 frozen strawberries
  • 3–4 sliced frozen peaches
  • 1 tbsp. agave nectar
  • 1 tbsp. peanut butter
  • 1 tbsp. Truvia
  • 1 cup almond milk
  • 1/4 cup strawberry Chobani yogurt


  1. Combine in blender until smooth.

- Eric Bockelman, RD, LD

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Katherine is our Content Champion. She has done triathlons in the past, and now focuses on mountain biking and long-distance gravel riding. She still has a soft spot in her heart for weird multi-sport events like indoor triathlon and aquabike. She also teaches indoor cycling.

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