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 even low-intensity 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.
Int J Sports Med. 2007 Jun;28(6):531-8.