Proteins and Exercise
When athletes do high intensity strength training, then they need extra protein.
True (half true). Strenuous exercise causes low glutamine concentrations, which is important because glutamine comprises 60% of total amino acid (AA) pool. Prolonged strenuous exercise increases protein breakdown and also increases protein synthesis during recovery. Therefore protein stimulates muscle growth and to build muscle, you have to be in a positive (+ ve) nitrogen balance. Due to the high protein intake, extra AA’s are oxidized for energy. To maintain strength, a person only needs 0.9 g/kg/day. For increased strength and lean body mass, they need 1.4 – 1.8 g/kg/day protein. But the average person’s protein intake is approximately 1.5 – 2.0 g/kg/day, which is enough to meet the requirements for most athletes following a balanced diet. This reason why I say only half true. Therefore to improve protein synthesis, the type of protein ingested is just as important as the amount of protein, very important is ingesting the essential AA’s. Amount of intake also very individual specific, doesn’t matter how much protein you take in, if you don’t use all of the protein ingested, the excess will always be converted to glucose and fats.
Endurance athletes do not need more protein than provided in a balanced diet.
True. Only high intensity endurance athletes need extra protein due to increased protein catabolism. The recommended amount of protein intake for high intensity endurance exercise is 1.2 – 1.6 g/kg/day would be sufficient, where as the average person’s protein intake is 1.5 – 2.0 g/kg/day. Therefore protein intake is sufficient, but what would improve effectiveness is following a balanced diet including only the essential AA’s which leads to a doubling of the protein synthesis effectiveness.
A high protein diet is a good way to loose weight.
True. Consuming high amounts of essential proteins will increase the synthesis of protein, when combined with a well balanced lifestyle including daily exercise. Deamination of intracellular AA’s will lead to increased fat synthesis. For individuals with normal renal function, the risks are minimal and must be balanced against the renal and established risk of continued obesity.
To build muscle, CHO and protein must be taken in together during the recovery phase after exercise.
True. During exercise, glycogen depletion takes place and muscle breakdown occurs. Recovery is important for the restoration of muscle and liver glycogen stores, replacement of fluid and electrolytes lost in sweat, and the regeneration, repair and adaptation processes following the catabolic stress and damage caused by the exercise. Supplementation directly after exercise will increase protein synthesis, contribute to a + ve nitrogen balance, increase the fat oxidation rate as well as increase muscle glycogen storage.
Fats and Exercise
Why does regular low-intensity exercise stimulate greater body fat loss than high intensity exercise of equal total caloric expenditure?
Endurance training increases the capacity of the carrier molecule to transport free fatty acids (FFA); therefore the muscles of regular trained individuals can take up more FFA at the same FFA concentration in the plasma. During high intensity exercise and adequate carbohydrate (CHO) reserves, CHO is preferred as fuel source. But at low intensity exercise, FFA supplies up to 80% of total energy required, therefore a higher rate of fat oxidation. High intensity exercise causes increased levels of lactate concentration in the blood, which also contributes to the inhibition of FFA oxidation.
If the average person stores enough energy as body fat to power 120hrs exercise at marathon race pace, why do athletes often experience impaired performance towards the end of a marathon performed under high-intensity, steady-rate aerobic metabolism?
At low intensity exercise, lipolysis supplies sufficient enough FFA to meet the muscles’ energy supply. During high intensity exercise, lipolysis is markedly suppressed and the FFA oxidation is diminished due to increased concentrations of lactic acid produced. The average person is not as well trained as a marathon runner, and therefore his body will react different to high intensity exercise. Comparing both athletes above mentioned, when running at the same pace, the average person would work at a much higher rate and a have much higher energy expenditure than the trained marathon runner. Therefore at the same pace, the marathon runner would use less oxygen than what the average person would use. Therefore the average persons would have a higher lactic acid concentration in his blood which suppresses FFA usage for energy, and therefore be using more CHO as an energy source. To conclude, by comparison, at the same pace, the average person’s oxygen consumption (%VO2) would be much higher than the trained marathon runner, therefore oxygen demands less contributing to a better running efficiency.