There’s been a number of studies showing that adding leucine to a standard dose of whey protein (i.e. 20g-25g) can serve to boost the muscle protein synthesis following resistance exercise. These findings are reflected in many contemporary whey protein powders that now include added leucine and/or BCAAs. But the question of whether the same principle applies to recovery from endurance exercise has not been answered adequately up until now.
Researchers from multiple countries including New Zealand, Australia, Canada, US and Switzerland pooled together to devise a smart study which set out to determine the most nutritionally efficient way of improving muscle recovery following endurance exercise. To do this, they compared the effect of two significantly different doses of whey protein and leucine combined with carbohydrate and fat. The low dose group received a total of 23.3g of whey protein, 5g of leucine, 180g of carbohydrate and 30g of fat; spread across 4 doses over 90 minutes. In contrast, the high dose group received 70g of whey protein, 15g of leucine and the same amount of fat and carbs. There was also a control group who just received an isocaloric amount of carb and fat (i.e. 270g and 30g respectively).
The supplements were administered after a standardised intense 100 min cycling bout that involved a series of different threshold intervals ranging from 2 to 8 mins. The athletes (i.e. 12 endurance-trained cyclists with an average VO2max of 60.4 mL/kg/min) were then monitored throughout a 4-h recovery period during which they provided blood samples at 0, 15, 30, 60, 90, 120, 180 and 240 minutes as well as two muscle biopsies at 30 and 240 minutes. That's alot of pricking and proding, which allowed the researchers to provide some very advanced and insightful measures. On top of blood levels of amino acids, glucose and insulin, they also measured the expression of a wide number of proteins related to muscle protein synthesis and turnover. These valuable measures provided insight into the strength of the molecular signals at the level of the muscle cells, and the mechanisms which ultimately govern the physical response of muscle tissue to endurance exercise.
While the study provided some very sophisticated molecular measures of the comparative effect of two significantly different doses of whey protein + leucine, it’s beyond the scope of this article to go into great depth about them. The main takeaway was that ingestion of 23g of whey protein and 5g of leucine in the 90-min period following intense endurance exercise was sufficient to stimulate a reasonably high rate of muscle protein synthesis compared to the higher dose of 70g whey protein and 15g leucine. This was despite the fact that the high protein group achieved substantially higher blood levels of leucine and essential amino acids in addition to expression of key proteins involved in regulation of muscle growth. The findings of the study suggest that a low dose whey protein + leucine has much greater nutrition efficiency when it comes to improving muscle function and subsequent performance following an intense endurance exercise bout. This is great news for all endurance athletes that are on a budget and looking to optimise their nutritional supplementation for enhancing recovery.
Rowlands DS, et al. Protein-leucine fed dose effects on muscle protein synthesis after endurance exercise. Med Sci Sports Exerc. 2014 Jul 14. [Epub ahead of print]