Study under review: Branched-chain amino acid supplementation and exerciseinduced muscle damage in exercise recovery: A meta-analysis of randomized clinical trials
The stiffness and soreness you experience days after an intense or novel workout is called delayed-onset muscle soreness (DOMS). It is caused primarily through direct damage to muscle fibers and the consequent inflammatory response necessary for repair. Although completely normal and not harmful by itself, DOMS can be uncomfortable and increase the risk of injury at subsequent workouts. Accordingly, it is worthwhile to investigate ways to reduce DOMS.
Leucine, isoleucine, and valine possess a similar structure, shown in Figure 1, and are referred to as branched-chain amino acids (BCAAs).They are essential amino acids that account for about 35% of the essential amino acids in muscle proteins. It has been well established that BCAAs, especially leucine, promote muscle protein synthesis and help stimulate the repair processes that ultimately lead to larger and stronger muscles.
A recent systematic review investigating the hypothesis that BCAA supplementation can alleviate exercise-induced muscle damage concluded that the number of randomized controlled trials reporting a positive effect was equivalent to the number of studies that showed no effect. The studies included in this review used ratings of muscle soreness and indirect biomarkers of muscle damage, such as creatine kinase (CK) and lactate dehydrogenase (LDH). Ultimately, the authors of this systematic review cautioned that the potential beneficial effects of BCAA supplementation require further testing with larger controlled trials, since most studies involved relatively small sample sizes (six to 15 participants per group). Importantly, this systematic review did not include a meta-analysis and was purely qualitative.
To date, no meta-analysis has pooled the data of clinical trials investigating the effects of BCAA supplementation on DOMS and muscle damage. By pooling the data from these studies, a meta-analysis can largely overcome the limitations of small studies and increase the statistical power to detect whether a true effect exists. Accordingly, the study under review was a meta-analysis of randomized controlled trials on this very topic.
Exercise-induced muscle damage tends to cause soreness in the days following a workout. This is called delayed onset muscle soreness (DOMS). There is some evidence from controlled trials that BCAA supplementation can help alleviate DOMS and reduce muscle damage, but these studies are small and conflict with one another. The study under review was a meta-analysis of randomized controlled trials investigating the effects of BCAA supplementation on exercise-induced muscle damage and soreness.
Other Articles in Issue #38 (December 2017)
Interview: Jorn Trommelen, PhD(c)
In this interview, Jorn delves into the details of his research on presleep protein. He discusses how it can be applied to help promote muscle growth and address open research questions in this area.
When beetroot supplementation doesn’t involve nitrates
There’s evidence to suggest that the nitrates in beetroot juice can help improve performance. Are there other components in it that also have an effect?
The enduring mystery of caffeine’s ergogenic effects
Caffeine’s ability to boost exercise performance is well known. Exactly how it does so is a little less clear.
Can vitamin K reduce body fat accumulation in postmenopausal women?
The hormone osteocalcin regulates bone density and fat mass, and vitamin K is necessary for its activation. This suggests that supplementation could affect fat mass.
Boosting the flu shot with prebiotics and probiotics
The flu shot does not always lead to antibody production. Supplementing with prebiotics or probiotics may help.
Sensing caloric density: can we eat less if we eat more?
Can preloading with low energy density foods eaten slightly before a meal reduce overall food intake?