Resistance type training elicits the oxidation of the amino acid leucine.
This has consequently shown to decrease plasma and serum concentrations by approximately 30% (Mero, 1999). Leucine oxidation increases during exercise in an intensity-dependent manner and may contribute 2–3% of total energy expended during an exercise session. Branch chain amino acids (BCAA) consist of three amino acids; leucine, isoleucine, and valine, which comprises of one third muscle protein (Lemont et al, 1999). The leucine composition of a protein source has been identified as a key regulator in protein synthesis, thus dictating the rate of recovery and muscle hypertrophy initiated from resistance exercise (Pencharz et al, 2012). Therefore, if leucine intake is sufficient to meet the training demands, then protein synthesis, thus recovery will be optimised to elicit the desired training adaptation.
Leucine intake through supplementation or diet arises particular interest as it has been identified as a key regulator in protein synthesis through the activation of mammalian target of rapamycin (mTOR). In short, mTOR activates ribosome S6K1 which stimulates the translation of mRNA, thus creating new muscle protein (Pencharz et al, 2012). Therefore, ingesting leucine around exercise may accommodate for the loss during strength training whilst promoting the anabolic signalling cascade. Paddon-Jones et al (2004) have suggested that an acute ingestion of 3-4g of leucine is required per serving to maximise protein synthesis, which can be found in approximately 30-40g of whey protein. Finally, Leucine has been shown to aid with the update of dietary amino acids and the re-uptake of catabolised amino acids caused through training.
Therefore combining Leucine with other amino acids may be beneficial for increased rates of recovery from training, specifically hypertrophy and strength training. I.e.a mixed amino acid based meal; whey protein, meat, fish, dairy products etc.