Endurance athletes are often encouraged to consume carbohydrates during prolonged exercise. There is no doubt that this is vital for maximizing performance as carbohydrates are the preferred fuel source but body stores are limited, making carbohydrate consumption during exercise importance. However, during aerobic exercise, such as running or cycling, a small amount of muscle protein will also be used as an energy source. As a reminder, protein is made up of chains as of amino acids. This muscle protein is broken down into amino acids that can then be used by the working muscle as a fuel source.

Muscle protein is more likely to be used as fuel with:

  • More intense and longer exercise
  • Training with low muscle carbohydrate stores, such as athletes following a low carbohydrate diet
  • Male athletes
  • Athletes eating a high protein diet

As I mentioned last week, the use of muscle protein as energy source during aerobic exercise is one of the reasons endurance athletes can actually have higher protein requirements than strength athletes. While consuming protein in the form of amino acids during exercise has not been shown to improve performance, it can improve protein balance. This is because consuming amino acids during exercise can provide a protein sparing effect, so that protein consumed after exercise can be more readily utilized to help repair muscle damage resulting from exercise.

The practice of consuming amino acids during exercise is useful for athletes engaging in prolonged endurance events such as marathoners, ironman athletes or ultra-distance runners. The amount of amino acids recommended to consume is at most 0.2 grams/kg body weight per hour. For instance, this would be up to 14 grams per hour for a 160 lb athlete. This is in addition to consuming 60-90 grams of carbohydrate per hour.

Some gels have amino acids added to them, but they tend to be smaller quantities. For instance, GU roctane gels have about 1.5 grams of amino acids. If you’re consuming three of these per hour to also meet your carbohydrate requirements, you’d be getting about 4.5 grams of amino acids. Some electrolyte drinks also have added amino acids such as a GU roctane energy drink mix or Biosteel Sports Hydration Mix. Another alternative is selecting real food that has some protein in it such as a peanut butter sandwich. This is a great option for those in ultra-distance events to prevent flavour fatigue. For more real food ideas, click here.

While consuming carbohydrates during exercise is essential for endurance athletes to perform at their best, also consuming amino acids could help with muscle protein balance. While this may not directly improve sports performance, it could help endurance athletes recover faster and get the most out of their training and competition by keeping them healthy and strong.

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Categories: Megan Kuikman

Megan Kuikman

Hello! I’m Megan Kuikman. I’m a Registered Dietitian with specialized training in sports nutrition. My goal is to help athletes and active individuals achieve a healthy attitude towards health, training, and food. I empower athletes to fuel properly for training in order to restore their health and enhance performance. You can get in touch with me at: hello@megankuikmanRD.ca


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