Branched-chain amino acid supplementation and exercise-induced muscle damage in exercise recovery: A meta-analysis of randomized clinical trials

Highlights

• Branched-chain amino acids (BCAAs) significantly reduced creatine kinase for up to 24 h.

• BCAAs demonstrated no beneficial effects in any of the follow-up times for muscle soreness and lactate dehydrogenase.

• BCAA is better than passive recovery or rest after various forms of exhaustive and damaging exercise.

Abstract

Objective

Accumulating evidence suggests positive effects of branched-chain amino acids (BCAAs) on moderate muscle damage. However, findings vary substantially across studies. The aim of this review was to examine the effect of BCAAs on recovery following exercise-induced muscle damage.

Methods

Controlled trials were identified through a computerized literature search and tracking of citations performed up to November 2015. To pool data, either a fixed-effects or a random-effects model was used; for assessing heterogeneity, Cochran's Q and I² tests were used.

Results

Eight trials met the inclusion criteria. Pooled data from the eight studies showed that BCAAs significantly reduced creatine kinase at two follow-up times (<24 and 24 h) in comparison with placebo recovery (<24 h: mean difference, –71.55 U/L, 95% confidence interval, –93.49 to –49.60, P < 0.000, n = 5 trials; 24 h: mean difference, –145.04 U/L, 95% confidence interval, –253.66 to –36.43, P = 0.009, n = 8 trials). In contrast, effects were not significant in any of the follow-up times for muscle soreness or lactate dehydrogenase.

Conclusion

The current evidence-based information indicates that use of BCAAs is better than passive recovery or rest after various forms of exhaustive and damaging exercise. The advantages relate to a reduction in muscle soreness and ameliorated muscle function because of an attenuation of muscle strength and muscle power loss after exercise.

Introduction

The benefits of regular exercise to improve health and prevent chronic disease are well known. However, exceptional and sudden exercise results in ambiguous pain in the skeletal muscle within hours or days during recovery after exercise, which is referred to as delayed-onset muscle soreness (DOMS) [1]. DOMS is a symptom of exercise-induced muscle damage (EIMD). EIMD is defined as a decrease in neuromuscular function, reduced range of movement, increased muscle soreness (MS), limb swelling, and the elevation of intramuscular proteins in blood [2]. DOMS is commonly an unpleasant feeling and can adversely affect muscle efficiency from voluntary reduction of effort, as well as from the muscles’ intrinsic loss of capacity to generate force [3]. Therefore, it is favorable to reduce exercise-induced DOMS not only in athletes but also in untrained individuals [4].

Branched-chain amino acids (BCAAs; valine, leucine, and isoleucine) are abundant and catabolized in the skeletal muscle, help to prevent protein breakdown [5], [6], and elevate protein synthesis [7]. The effects of BCAA supplementation on increased plasma creatine kinase (CK) and lactate dehydrogenase (LDH) activity and DOMS have been controversial and the factors that account for these differences remain unclear. Studies examining recovery from heavy endurance activity [1], [8] have reported evidence that BCAAs are advantageous in decreasing muscle damage and in accelerating the recovery procedure. In a well-controlled example [9], MS was decreased with the use of BCAAs. It should be noted that accumulating data suggest positive effects of BCAAs on moderate muscle damage. However, findings vary substantially across studies. Therefore, we aimed to conduct a meta-analysis from randomized controlled trials (RCTs) to specify the effects of BCAA supplementation on MS and indirect markers of muscle damage in all studies with this subject.