Essential amino acids and muscle protein recovery from resistance exercise
Muscle protein synthesis (protein production) increases during recovery from resistance exercise. But muscle protein breakdown also occurs, which blunts the muscle-building effect of resistance exercise, as muscle protein balance, though improved, remains negative. To gain a positive net protein balance, nutrient intake is necessary.
Previous studies have shown that ingestion of a small amount (6 grams) of amino acids plus 35 grams of carbohydrates increases muscle protein synthesis 3.5-fold. Before this study, the independent effects of amino acids were not known.
Acute metabolic study
Number of Subjects
The principal aim of this study was to determine if 6 grams of essential amino acids (EAAs) alone could effectively stimulate muscle protein synthesis after resistance exercise. The secondary aim was to compare the effects of 6 grams of essential amino acids to a 6-gram mixture of essential amino acids plus nonessential amino acids (NEAAs). Researchers also investigated the effect the initial dose of 6 grams of EAAs would have on a second dose 1 hour later.
The study used stable isotope tracer methodology to quantify muscle protein synthesis, breakdown, and net balance. Results showed that approximately 3.5 ± 1.1 grams of muscle protein were synthesized for 3 hours after the initial dose of essential amino acids, and a total of 7.0 ± 2.0 grams after both doses, for a net gain of approximately 26 grams of synthesized muscle tissue. The EAA dose given 2 hours after exercise had a similar effect on net muscle protein synthesis as the dose ingested 1 hour post exercise.
There is a dose response of muscle protein synthesis to EAA ingestion after exercise. Because the muscle net balance response was double the response to two doses of a formula of 3 grams of EAAs + 3 grams of NEAAs reported in a parallel study, researchers concluded that NEAAs are not needed to stimulate muscle protein synthesis after exercise.
EAAs increase net protein balance without the help of carbs
Results indicate that supplementing with 6 grams of EAAs without the addition of carbohydrate significantly increases muscle protein synthesis post resistance exercise. Additional carbohydrates showed no advantage to ingesting essential amino acids alone, as demonstrated by Figure 1.
Resistance exercise primes the body for muscle building, but without proper nutrient intake during the recovery period, all that hard work can be for naught. Essential amino acids are the building blocks for the muscle protein you’re attempting to build, and two doses of 6 grams of EAAs taken 1 and 2 hours after resistance exercise can help build approximately 26 grams of newly synthesized muscle tissue, thereby supporting the health of your muscles and your workout gains.
Børsheim E, Tipton KD, Wolf SE, Wolfe RR. Essential amino acids and muscle protein recovery from resistance exercise. Am J Physiol Endocrinol Metab. 2002;283(4):E648-E657. doi:10.1152/ajpendo.00466.2001