Leucine, isoleucine and valine are three main branches of the branched-chain amino acids (BCAA), and make up about one-third of muscle protein. Of this, leucine is the most thoroughly researched due to its higher oxidation rate a compared to valine and isoleucine.

During aerobic, anaerobic and strength exercise, significant decrease is seen in leucine from 5 to 33%. Hence it is important to meet the leucine requirement.

Significant decreases in plasma or serum levels of leucine occur following aerobic (11 to 33%), anaerobic lactic (5 to 8%) and strength exercise (30%) sessions. The protein protein does contain the leucine, but its content may vary between 5 and 10%. There are suggestions that the current recommended dietary intake of leucine be increased from 14 mg/kg bodyweight/day to a minimum of 45 mg/kg bodyweight/day for sedentary individuals, and more for those participating in intensive training in order to optimize rates of whole body protein synthesis.(Mero A;1999)

Studies suggest that BCAA containing approx.30 to 35% of Leucine before and after the endurance exercise may prevent protein breakdown,improve muscle glycogen stores, thus improve both mental and physical performance.

In one of the studies, during 5 weeks of strength and speed training, leucine supplementation of 50 mg/kg bodyweight/day, supplementary to a daily protein intake of 1.26 g/kg bodyweight/day, appeared to prevent the decrease in the serum leucine levels in power-trained athletes. According to 1 study, dietary supplementation of the leucine metabolite beta-hydroxy-beta-methylbutyrate (HMB) 3 g/day to humans undertaking intensive resistance training exercise resulted in an increased deposition of fat-free mass and an accompanying increase in strength.

The studies are clearly telling us that leucine supplementation is a must for endurance and strength exercise:

• Exercise increasing your protein breakdown and protein requirement, but at the same time it decreases the ability to synthesize muscle protein. Leucine can help improve the muscle protein synthesis, if taken before your workout.
• Leucine belongs to essential  amino acids required for the proper muscle synthesis, thus may lead to muscle-building to optimize your workout.
• Leucine ability to reduce muscle breakdown or loss is not only beneficial for athletes but also for older people. 
• Leucine is also responsible for improving your fat loss journey as compared to the valine and isoleucine. This way, your lean muscle mass is improved.
• A review from the Department of Food Science and Human Nutrition at the University of Illinois reported that consuming leucine right after working out can help stimulate muscle recovery.  

GNC BCAA contains 6g of Instantized BCAA in optimal 2:1:1 to prevent muscle breakdown during intensive workout. GNC BCAA can help support muscle strength for intensive workouts to promote muscle growth Reduce muscle fatigue and improve recovery time.