Rate of Protein Oxidation in Extreme Exercise

During exercise, your body begins to break down down stores of carbohydrates, fat, and protein to turn into usable energy. While your body prefers to break down stored carbohydrates, during longer periods of high-intensity exercise, these carbohydrate stores will be depleted. Extreme exercise results in a higher rate of protein breakdown for energy also known as protein oxidation.

  1. Energy Sources During Exercise

    • Your body burns different fuels throughout a workout, depending on the type of exercise and duration. During the first few minutes of exercise, carbohydrates are the main source of energy. Your body will then begin to break down fat to use as fuel and finally protein. However, during the first hour of exercise, proteins make up less than 2% of fuel sources. Only in extreme or prolonged exercise, does your body start to oxidize protein into usable energy.

    Rate Of Protein Oxidation

    • When you perform extreme or prolonged exercise, your body turns to protein as an energy source. Protein oxidation may range anywhere from five to 15% of the fuel supply during exercise periods of three to five hours. In intense exercise conditions, protein can supply up to 10% of the total energy requirements. Your body prefers to break down glygocen and fat for energy, but will use protein as needed. However, the amount of protein used varies depending on an individual's glycogen and fat stores.

    Specific Amino Acids Oxidized

    • Protein is comprised of individual amino acids bonded together and during exercise, your body oxidizes certain amino acids at a higher rate than others to spare muscle tissue and provide rapid energy. The amino acids leucine and alanine are preferentially broken down to form energy in all types of endurance exercise. However, glutamine is only released and broken down in extreme exercise.

    Protein Sparing During Exercise

    • Although your body will use muscle protein during exercise, your body prefers to spare protein as much as possible. Although in normal conditions, your body breaks down and excretes used amino acids in the urine, exercise changes protein excretion. Instead of being released into the urine, amino acids are instead taken up by the body and used for fuel to spare muscle protein. This change in metabolism ensures adequate energy and decreases the rate of protein breakdown from muscle tissue.