Small amount of BCAAs and L-arginine prevents cardio-induced muscle breakdown

A cardio session – especially when done after strength training – has lots of positive health effects, but cardio exercise breaks down muscle tissue. For strength athletes cardio is a double-edged sword. Researchers at Otsuka Pharmaceutical in Japan think you can make one side of the sword less sharp by taking 2 g BCAAs and 0.5 g arginine.

High doses of BCAAs reduce muscle breakdown during physical exercise and boost the body’s anabolic response. The researchers wanted to know whether lower doses of BCAAs supplemented with a small amount of L-arginine might do the trick as well.

The Japanese did an experiment with 4 men and 4 women, all of whom were healthy, in their mid-twenties and untrained. The subjects were given breakfast, after which they had to cycle three times for 20 minutes at 50 percent of their maximal intensity. They rested for 5 minutes between each session.

Ten minutes after starting this anything but intensive workout, the subjects took their amino acids, dissolved in a sports drink. The method of administration gives an indication of the researchers’ intentions. Then the researchers repeated the experiment, but gave the subjects a placebo.

The researchers measured the amount of amino acids that the subjects absorbed and excreted during the workout via a catheter inserted into the leg. The more amino acids released from a leg, the greater the muscle breakdown, the researchers reasoned.

The tables below show the net effect: the uptake in the leg minus the release. As you can see, the supplement reduced the release of glutamine and alanine.


The effect was greatest at the end of the workout – during the third session. The figures are for phenylalanine. If you look at this amino acid, the mix of BCAAs and L-arginine blocks muscle breakdown almost completely during the third workout.


The anticatabolic effect of the amino acid-laced sports drink would probably have been greater if the test subjects hadn’t drunk it during the workout but beforehand. Higher doses would undoubtedly have had a greater anticatabolic effect.

The research results suggest a strategy that could well give strength athletes more benefit from doing cardio after their weight training: take a dose of BCAAs and L-arginine before getting on the treadmill.

Branched-chain amino acids and arginine supplementation attenuates skeletal muscle proteolysis induced by moderate exercise in young individuals.


This study aimed at evaluating the effect of a single oral intake of branched-chain amino acids (BCAA) with Arg on skeletal muscle protein metabolism during moderate exercise in young individuals. Eight healthy volunteers (4 males and 4 females, means +/- SEM, 26 +/- 1 yrs, 177.8 +/- 3.7 cm, 72.6 +/- 3.9 kg) were studied in a randomized double-blind placebo-controlled cross-over trial. The subjects performed 3 bouts of 20-min cycling exercise (5-min break between each bout) at 126 +/- 13 W corresponding to 50 % of the maximal work intensity. A single oral supplement of either a BCAA drink containing 2 g of BCAA and 0.5 g of Arg or an isocaloric placebo drink was given at 10 min of the 1st exercise bout. Both arterial and venous blood samples were simultaneously taken from the radial artery and the femoral vein, respectively. Blood flow in the femoral artery was determined using the ultrasound Doppler technique. The blood sampling and blood flow measurements were performed at rest, every 10 min during each exercise bout. Net balance of BCAA and Phe across the leg muscles were measured by the arteriovenous difference method. The BCAA ingestion resulted in increases in both the plasma BCAA concentration and BCAA uptake into the working leg. The Phe release from the leg during exercise significantly increased as compared to the basal level in the placebo trial (0.97 +/- 0.28 vs. 0.23 +/- 0.22 micromol/min, p < 0.05). In the BCAA trial, the cumulative Phe release from the leg during the 3rd exercise bout was significantly lower than that in the placebo trial (5.0 +/- 7.4 vs. 35.9 +/- 13.2 micromol/25 min, p < 0.05). These results suggest that endurance exercise at moderate intensity enhances proteolysis in working muscles, and a single oral intake of 2 g of BCAA with Arg at onset of exercise effectively suppresses exercise-induced skeletal muscle proteolysis. PMID: 17497593 [PubMed - indexed for MEDLINE] Source: