Leucine can substitute for a complete protein meal
For several years taking branched chain Amino Acids were advocated pre-workout, but taking leucine may be the only amino acid necessary as muscle protein stimulation is responsive to stimulation by leucine, but not the other branched-chain Amino Acids, isoleucine and valine13.  Leucine seems to be the most potent of the BCAA with regard to most of these effects and therefore may be the most physiologically relevant.  Leucine alone can substitute for a meal in stimulating signal transduction pathways, leading to a stimulation of protein synthesis. Large oral leucine dosages increased muscle protein synthesis within 20 min. similar to meal feeding; the activity of the mTOR-signaling pathway in muscle is augmented following the oral leucine consumption.  So when getting ready for a show, consuming extra leucine can enhance protein synthesis.

Leucine Increases Protein Synthesis Independent of Insulin
Leucine has both anabolic effects in skeletal muscle reflecting both stimulated protein synthesis and inhibited protein breakdown. Studies suggest that some of the anabolic effects of leucine are regulated by mechanisms similar to those regulating the effects of insulin20, 21. Leucine is now known to interact with the insulin-signaling pathway with apparent control of protein synthesis, resulting in maintenance of muscle protein during periods of restricted energy intake.  Leucine appears to also stimulate protein synthesis independent of insulin17.  For example, a dosage of leucine resulted in a stimulation of protein synthesis that was independent of changes of plasma insulin concentrations, whereas a dosage containing carbohydrates (glucose plus sucrose) that raised insulin concentrations over 2.5 times the fasting glucose concentration did not affect protein synthesis3.  Overall the results demonstrate that leucine can cause increases in protein synthesis rates that are independent of insulin. 

Anti-Catabolic Actions of Leucine
Oral intake of leucine stimulates muscle protein synthesis after exercise or an overnight fast18, 19. These studies support the role of leucine as a key amino acid for reversing catabolic conditions which may be especially important when trying to get ripped for a competition In previous studies, there is evidence that catabolic conditions, muscles tissue becomes resistant to some of the anabolic effects of leucine22, and it is possible that this “leucine resistance” reflects why cortisol breaks down muscle tissue. More recent studies from laboratories provided direct evidence for a role of cortisol in “leucine resistance” in skeletal muscle. For example, Shah et al.6 reported that cortisol opposes the control of protein synthesis by leucine in skeletal muscle. Additionally, Rieu et al. 7 examined the effects of cortisol in young (4–5 wks), adult (10–11 months), and old (21–22 months) rats and made the interesting observation that cortisol induced leucine resistance in adult and old rats, but not in young rats. Considering those findings, the authors speculated that muscle loss during aging may reflect cortisol- induced “leucine resistance.”  This may be the reason why you do just about anything in the gym and still grow however with aging the gains are not as apparent.  Fasting and calorie restriction also results in an increase in leucine appearance rate in the blood, an index of whole body protein breakdown.  The increase in leucine appearance is consistent with a decline in insulin, because insulin normally suppresses protein breakdown.  Additionally, fasting increases the hormone glucagon which has a catabolic effect on leucine23.  In skeletal muscle, exposure to cortisol is characterized by a reduction in protein synthetic rate coincident with hampered protein synthesis rates; however oral administration of leucine reversed the catabolic effects of with a 1 hour of administration24.  It seems that intense training and calorie restriction both increase cortisol however leucine seems to counteract the negative effects of cortisol.