Title: Acute response of net muscle protein balance reflects 24-h balance after
exercise and amino acid ingestion.
Researchers: Tipton KD, Borsheim E, Wolf SE, Sanford AP, Wolfe RR.
Institution: Metabolism Unit, Shriners Hospitals for Children, Galveston, Texas.
Source: Am J Physiol Endocrinol Metab. 2003 Jan;284(1):E76-89.
Summary: The purpose of this study was to determine if the acute anabolic muscle
response to resistance exercise and essential amino acids (EAA) reflects the
response over 24 h.
Methods: Seven subjects participated in the following two 24-h studies: 1)
resting (REST) and 2) rest plus resistance exercise and consumption of pre- and
post essential amino acids (ES). Net balance (NB) across the leg was determined
for four amino acids. [(13)C(6)] phenylalanine was infused to determine mixed
muscle fractional synthetic rate (FSR).
Results: Twenty-four-hour FSR was significantly greater for ES than for REST (P
= 0.003). Exchange of phenylalanine across the leg was -194 74 (SE) mg for ES
and -371 88 mg for REST (P = 0.07) over 24 h and 229 42 mg (ES) and 28 15 mg
(REST; P < 0.01) over 3 h corresponding to exercise and EAA consumption for ES.
The difference in phenylalanine exchange between REST and ES was not different
for measurements over 24 and 3 h. Increases in NB during ES were primarily the
result of increases in protein synthesis. Results for other amino acids were
similar.
Conclusion: The acute anabolic response of muscle to EAA intake and exercise is
additive to the response at rest and thus reflects the 24-h response.
Discussion: This study may seem confusing at first, but once you know the
background assumptions that gave them the idea to perform this study, it all
makes sense.
It is known that as you increase your daily protein intake, your body will
compensate by increasing protein losses during the night.(1-4) So there is a
diurnal regulation of protein balance. This is the reason why simply eating more
protein doesn’t make you bigger and bigger. The more protein you eat, the more
protein your body gets rid of while you sleep.
Despite this observation, it is also known that carefully timing your protein
intake around your training can significantly increase protein synthesis in
muscle tissue. (5,6) So, it begs the question, does the anabolic effect of pre
and post exercise protein supplementation lead to a net increase in muscle
protein? The results of this study confirm that it does!
The increased protein synthesis that occurs with pre-and post exercise protein
supplementation lead to durable increases in muscle protein over a 24 hour
period, even in light of the diurnal regulation of whole body protein balance.
The nighttime protein losses did not reflect the additional protein taken in as
a pre- and post workout supplement. Thus the acute stimulation of muscle protein
by exercise and protein ingestion is additive to the balance that normally
occurs in resting muscle.
This study only enforces the importance of proper protein supplementation. By
proper I don’t mean just quantity, I mean using protein supplements in such a
way that ensures the greatest anabolic response. Normally, I try to avoid
mentioning specific supplements when discussing research, but Primer and Driver
are specifically designed to maximize the anabolic effects of training and
protein supplementation. If you are using HST and not using Primer pre-workout
and Driver post workout, you are missing out on significant gains. Ok, I just
had to get that off my chest.
References:
1: Millward DJ. Metabolic demands for amino acids and the human dietary
requirement: Millward and rRvers (1988) revisited. J Nutr. 1998 Dec;128(12
Suppl):2563S-2576S.
2: Quevedo MR, Price GM, Halliday D, Pacy PJ, Millward DJ. Nitrogen homoeostasis
in man: diurnal changes in nitrogen excretion, leucine oxidation and whole body
leucine kinetics during a reduction from a high to a moderate protein intake.
Clin Sci (Lond). 1994 Feb;86(2):185-93.
3: Price GM, Halliday D, Pacy PJ, Quevedo MR, Millward DJ. Nitrogen homeostasis
in man: influence of protein intake on the amplitude of diurnal cycling of body
nitrogen. Clin Sci (Lond). 1994 Jan;86(1):91-102.
4: Pacy PJ, Price GM, Halliday D, Quevedo MR, Millward DJ. Nitrogen homeostasis
in man: the diurnal responses of protein synthesis and degradation and amino
acid oxidation to diets with increasing protein intakes. Clin Sci (Lond). 1994
Jan;86(1):103-16.
5: Tipton KD, Rasmussen BB, Miller SL, Wolf SE, Owens-Stovall SK, Petrini BE,
Wolfe RR. Timing of amino acid-carbohydrate ingestion alters anabolic response
of muscle to resistance exercise. Am J Physiol Endocrinol Metab. 2001
Aug;281(2):E197-206.
6: Tipton KD, Wolfe RR. Exercise, protein metabolism, and muscle growth. Int J
Sport Nutr Exerc Metab. 2001 Mar;11(1):109-32.
