Muscle Recovery And Performance Improved Consuming Leucine-Enriched Amino Acid Mixture

Man doing a bicep curl in black and white. back to us.
Image by Łukasz Dyłka from Pixabay

A leucine-enriched essential amino acid mixture helps untrained men reduce their level of muscle damage and aids muscle recovery.

A small study in Japan of men training for sports has shown that they can reduce the damage to their muscles if they supplement with a leucine-enriched essential amino acid (LEAA) mixture. The study was performed by researchers from Ajinomoto Co., Tsukuba University of Technology, the University of Tsukubu and the Hokkaido Nippon-Ham Fighters (Matsui et al., 2019).

The study was reported in the Journal of Physical Therapy Science.

The study covered eight days of supplementation and measured creatine phosphokinase (CPK) levels. CPK is a marker of muscle damage due to physical exercise.

When sports people or even those of us who do not do exercise on a regular basis do muscle damage, then we cause muscle damage in the affected muscles (Clarkson & Hubal, 2002). When muscles are damaged by exercise they leak proteins such as myoglobin and creatine phosphokinase (CPK) into the bloodstream (Munjal et al., 1983). The purpose of damaging muscles is help build them but in the long term. In the short term, muscle strength drops as does the range of motion. The ability to continue to do bouts of intense exercise to the same level also declines.

Supplementation with leucine and other essential amino acids, especially the BCAAs (branched chain amino-acids) has been shown to increase anabolism and reduce catabolism of muscle proteins. From that point of view, it is one of the main reasons for the sale of so many supplements. Leucine in particular activates various forms of muscle protein synthesis so it is a considerable component in muscle building supplements and helps with muscle recovery.

In the study, there were no changes taking place to the observed maximal isometric strength in those men doing the exercises. The results showed that a 3.6 g dose which included 21 mg leucine per body weight was effectively and efficiently absorbed. It was enough to raise the serum levels of the essential amino acids for  many hours following consumption of the supplement.

The Study

In the study, 10 untrained men in the sports sense with an average age of 23 took part in this study. None performed regular exercise, drank, smoked or took dietary supplements. The study was a randomized, double-blind cross-over study design. The men were randomly assigned. They were required to either consume 3.6 gram or an LEAA supplement which contained the following nine essential amino acids: leucine, 1.44 g; lysine, 0.6 g; valine, 0.4 g; isoleucine, 0.39 g; threonine, 0.34 g; phenylalanine, 0.24 g; methionine, 0.12 g; histidine, 0.06 g; and tryptophan, 0.03 g) per pack.  The placebo contained 3.6 g of maltitol per pack. The subjects took each pack three times per day for eight days. This was followed by a three-week washout period after which the men then crossed over to the other intervention group and was repeated for another eight days.

The men did a series of eccentric muscle exercises doing a single limb bicep extension (5 sets of 10 arm curls using the Biodex System 4. This would purposefully damage the muscles so that they leaked these markers. As well as measuring CPK and myoglobin in the blood serum, they also reported their levels of muscle soreness. Soreness would be explained by uncharacteristic muscle damage and swelling.


In both cases the serum CPK enzyme levels rose in both exercising groups. However, the increase was significantly lower in the LEAA group. This indicated there was less muscle damage with LEAA supplementation. They noticed no other significant differences between the groups for either levels of myoglobin release from the damaged muscles or indeed any changes in self-reported muscle soreness. The levels of CPK were still high after five days as was the level of soreness.

The research adds to the body of work on amino acid supplementation. The study concluded that LEAA consumption suppressed exercise-induced elevation of muscle damage markers in blood. The study suggested that LEAA supplementation could stimulate muscle protein synthesis so attenuating muscle damage and aid muscle recover well in the process.


Supplementation with BCAAs is often questioned by those who believe they don’t actually have any physiological benefit, especially after doing exercise. The wider body of research though indicates that supplementation does help in reducing the time following muscle damage. However, the degree of recovery is often limited and not always as significant as many would like when doing extreme muscle based exercises. Such a study as this might benefit from involving a larger number of men of similar age and exercise prowess. There might also be further assessment of other objective measures including the men’s sporting performance.


Anthony, J.C., Yoshizawa, F., Anthony, T.G., et al. (2000) Leucine stimulates translation initiation in skeletal muscle of postabsorptive rats via a rapamycin-sensitive pathway. J Nutr., 130 pp. 2413–2419.

Clarkson PM, Hubal MJ (2002) Exercise-induced muscle damage in humans. Am J Phys Med Rehabil, 81 S52–S69.

Matsui, Y., et al., (2019) Effect of a leucine-enriched essential amino acids mixture on muscle recovery. J. Phys. Therapy Sci., 31(1) pp. 95-101 https://dor:10.1589/jpts.31.95

Munjal DD, McFadden JA, Matix PA, et al. (1983)  Changes in serum myoglobin, total creatine kinase, lactate dehydrogenase and creatine kinase MB levels in runners. Clin. Biochem., 16 pp. 195–199

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