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09.06.2010


GABA quadruples post-training growth hormone production

Strength athletes who take 3 g of the supplement GABA [structural formula shown below] quadruple their growth hormone production during and after a training session. Sports scientists at Shenandoah University discovered this when they did an experiment with 11 men (average age 23), all of whom were regular weight lifters.

GABA gamma-aminobutyric acid in full is a neurotransmitter found primarily in the brain. The body makes the compound from glutamate. GABA plays a role in relaxation; sedatives and sleeping pills like benzodiazepines and barbiturates work via the same receptor as GABA does. GABA is available on the market as a supplement, but you have to take huge amounts to notice any effect, as the brain cannot absorb it easily from the blood.

GABA stimulates the brain's production of growth hormone. Strength training does the same. The researchers wondered what happens if you do both: would the production of growth hormone increase even more?

GABA quadruples post-training growth hormone production

GABA
The researchers got their subjects to train their main muscle groups, doing chest presses, lat pull downs, flies, seated rows, shoulder presses, biceps curls, triceps extensions, leg-presses, leg-curls, leg-extensions and calf-raises. The subjects trained using 70 percent of the weight at which they could just manage 1 rep, doing 1 set of each exercise and resting for 1 minute between sets. The training session lasted 15 minutes.

On one occasion the subjects took 4 caps of GNC's GABA-750 [each cap contained 750 mg GABA], and on the other they took caps containing no active ingredient. The researchers repeated the procedure while the subjects rested. Even when the men were not training the GABA supplement raised their growth hormone level.


GABA quadruples post-training growth hormone production


The figure below shows levels of immuno-reactive GH. This is the fraction of growth hormone that is biologically active.

The researchers monitored the subjects' blood for 90 minutes. The figure below shows the total amount of active growth hormone the subjects made during the period.


GABA quadruples post-training growth hormone production


GABA increased the total amount of growth hormone the subjects made as a result of training by 480 percent. Whether strength athletes would lose fat or build up more muscle quicker in the long term as a result of this effect, the researchers do not yet know.

Source:
Med Sci Sports Exerc. 2008 Jan; 40(1): 104-10.

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