When we think of supplementing fuel sources, the few items that come to mind are carbohydrates and protein. When you get right down to it, starchy carbohydrates are nothing until they’re broken down into individual glucose molecules (and sometimes supplemented as such), and proteins are nothing until they’re broken down into amino acids. That’s right amino acids, including the branched chains, are the building blocks of proteins. The most active amino acids as it pertains to muscle function and recovery are the branched chain amino acids, or BCAAs, leucine, isoleucine, and valine. It stands to reason that, like glucose and starch, we can benefit from BCAA supplementation.
BCAAs, especially leucine, stimulate muscle protein synthesis, which is one half of the balance between breakdown and creation of muscle tissue. Like all bodily tissues, muscle is dynamic. That means it is constantly in a state of turnover. Increasing muscle protein synthesis does not automatically mean you’re going to become the hulk (it definitely does NOT), but it will aid the repair and recovery process. Moreover, illustrated in the diagram above, amino acids in combination with endurance exercise (vs. resistance exercise) contribute to mitochondrial biogenesis (vs. contractile proteins aka muscle size). More mitochondria = greater oxidative capacity and aerobic potential!
Rodents supplemented with a single dose of BCAA have improved endurance performance compared to glucose. However, the effects of a single dose of BCAA and glucose are not different from placebo in humans completing a 100km time trial. This study was a little fishy, though, because even glucose had no effect, and 100km is a pretty hefty distance without refueling (2). In other research, BCAAs supplemented daily over several weeks have reduced muscle damage, delayed time to fatigue, and improved power output. But more questions remain regarding sprint performance and immunology.
Researchers at Auburn University identified this gap in the literature and addressed it themselves (1). Using cyclists who had been training ~7 years and cycling ~200 km per week, they examined the effects of 10 weeks twice daily BCAA supplementation (6 grams). After the 10 weeks, cyclists supplementing with BCAAs improved peak power, mean power, and peak power relative to body weight during a Wingate sprint test. In a 4km time trial that followed the sprint, the BCAA group improved performance by 11% compared to no change in the control (maltodextrin) group. Measures of power during the time trial did not reach statistical significance, but the BCAA group had a visual improvement compared to another no change in the control group.
This is where things get a little interesting. Have you ever had a series of really hard training days and you start to become a little ill? Nothing very serious, just some sniffles, some light coughing, certainly nothing you can’t just train through? That is to say, it’s nothing you can’t train through until you get full-blown sick! Training is a physiological stressor, and when it comes to our response, it’s not all lilacs and daisies. Sometimes training either too much or combined with other sources of stress can lead to overreaching, sometimes overtraining. Well, proteins and amino acids have a substantial role in the immune system.
In this study, they took a look at immune markers. Typically, cyclists will have an increase in white blood cells and neutrophils, as these cells try to combat sickness. The BCAA supplemented group did NOT have the same increase in white blood cells and neutrophils as did the placebo group. That sounds like it could be a bad thing – like the potential to become ill may be increasing. That’s not the case, however.
The way neutrophils work is they roam around the blood stream, and when they locate pathogens or other “baddies,” they eat them. No joke. Because of BCAAs role in protein synthesis (in all cells, not just muscle cells), they are thought to enhance the appetite of neutrophils. BCAAs encourage neutrophils to get out there and Pac-Man some ghosts. The result for the athlete is better immune function instead of more immune cells. We like efficiency!
If not from an ergogenic standpoint, for recovery. The rebuttal is always, “why not just protein?” We like protein, too, and athletes need to pay careful attention to their protein intake. Advantages of BCAAs over protein are the amount needed to have a beneficial effect on muscle function, which may be as little as 2.5 grams for BCAAs versus 20g for a high-quality protein. This is also related to calories, fewer calories to stimulate protein synthesis with BCAA than protein for those who are dieting. Also, digestion is simplified. A reduced quantity of BCAA versus protein reduces the potential for gastric distress when consumed before, during, or after exercise. Disadvantages are that the BCAAs are not a complete protein. All-in-all, BCAAs are a good thing! It would only stand to benefit endurance athletes when supplemented before and/or during training. After training is a good time too, but we recommend whole protein at that time.
References1. Kephart, W. C., Wachs, T. D., Mac Thompson, R., Mobley, C. B., Fox, C. D., McDonald, J. R., ... & Pascoe, D. D. (2016). Ten weeks of branched-chain amino acid supplementation improves select performance and immunological variables in trained cyclists. Amino acids, 48(3), 779-789.