Abstract: Improving muscle mass

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The below abstract may be of interest:

Improving muscle mass: response of muscle metabolism to exercise,

nutrition and anabolic agents.Tipton KD, Ferrando AA.

Essays Biochem. 2008;44:85-98.

Muscle mass is critical for athletic performance and, perhaps more

importantly for most, health and survival. The metabolic basis for a

change in muscle mass is an increase in net muscle protein balance

(termed NBAL). NBAL is the difference between MPS (muscle protein

synthesis) and MPB (muscle protein breakdown).

Thus an increase in MPS and/or a decrease in MPB are necessary for

NBAL to increase, leading to accretion of muscle proteins. In

particular, accretion of myofibrillar proteins is necessary. NBAL

responds to exercise, feeding and other factors.

In healthy, weight-stable adults, muscle mass remains constant

because periods of positive balance following feeding are countered

by periods of negative balance during fasting. A combination of

resistance exercise and nutrition is a potent anabolic stimulus

through stimulation of MPS from amino acids and attenuation of MPB by

carbohydrates.

Increased muscle mass results from the accumulation of small amounts

of protein in response to each bout of exercise combined with

nutrient intake. The magnitude of the response may be influenced by

factors other than just the amount of a nutrient ingested. Timing of

ingestion, co-ingestion of nutrients and the type of protein may all

influence protein accretion. Testosterone is a potent anabolic

stimulus primarily through improvement in re-utilization of amino

acids from MPB.

There is a general lack of efficacy in studies assessing the

potential for growth hormone, androstenedione and

dehydroepiandrostenedione to increase muscle mass. Creatine

supplementation is clearly an effective means to increase muscle

mass, especially in combination with resistance exercise, however the

mechanisms remain unclear. Results from acute metabolic studies

provide useful information for estimation of the efficacy of anabolic

agents.

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Carruthers

Wakefield, UK