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01.04.2017

Taking leucine after strength training boosts IGF-1 concentration in muscle cells

Taking a couple of capsules of leucine or ursolic acid after a workout and nothing else probably won't do much for bodybuilders and other strength athletes, according to what American sports scientists wrote in the Journal of the American College of Nutrition. Their human studies suggest that these supplementation strategies don't lead to more muscle growth, even though leucine administration does lead to a dramatic increase in intramuscular IGF-1 in muscle cells.

Study
The researchers got nine men, all of whom had experience in weight training, to train their legs on three different occasions. Immediately after the workout the men took a placebo, a supplement containing 3 g leucine or a supplement containing 3 g ursolic acid.

The men did not eat before training. An hour after the workout, the men were given an Atkins bar containing 13 g fat, 8 g protein and 3 g carbohydrates. That's the only thing the participants ate.

The researchers took blood and muscle samples several times during the first six hours after the workout.

Results
The supplementation had no effect on the concentration of insulin or IGF-1 in the participants' blood. The researchers observed a slight increase in activity of the anabolic switch molecule mTOR in the muscle cells of the men in the placebo groups, but the differences were not statistically significant.

Ursolic acid boosted the activity of the IGF-1 receptor in the muscle cells six hours after intake, but that effect was not significant either. We wonder, however, whether this would have been the case if the researchers had had more participants in their experiment.

What was significant was the effect of leucine supplementation on the concentration of IGF-1 in the muscle cells.

Conclusion
The findings are not a complete surprise. We already knew that leucine supplementation is only effective when combined with other amino acids.

Suggestions, unfounded and without substance
The IGF-1 receptor in the muscle cells becomes more active six hours after consuming ursolic acid. Two hours after consuming leucine, the concentration of IGF-1 in the muscle cells increases. What would happen if strength athletes took ursolic acid three hours before starting a workout and leucine after finishing the workout? And did that in combination with other amino acids?

Source:
J Am Coll Nutr. 2016 Sep-Oct;35(7):627-38.

More:
The unprecedented possibilities of the Horny Goat Weed-leucine cocktail 13.03.2017
Strength training + glass of milk + tablespoon leucine = more muscle 20.09.2016
If leucine isn't stimulating muscle growth, try combining it with glycine 14.06.2016

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