Skeletal muscle contains high concentrations of histidine-containing dipeptides (HCD), in the form of carnosine, anserine, or ophidine. Carnosine, the only HCD found in humans, is related to high-intensity exercise performance 1. Beta-alanine is the rate-limiting amino acid for muscle carnosine synthesis. Long-term supplementation of beta-alanine was first shown to markedly enhanced humans muscle carnosine levels and improved high-intensity performance in 2006 2. Chronic supplementation with beta-alanine is ergogenic (performance enhancing) for cycling tests until exhaustion at 110% of maximal power 3. Regardless of the evidence for carnosine’s ergogenic effect during high-intensity exercise that lasts several minutes, carnosine’s role in the control of muscle contractile function is poorly understood.
The Research . . .
Recently, a study was undertaken to investigate the effect of increasing doses of carnosine and beta-alanine for several weeks on carnosine, anserine, and taurine muscle content in mice 4. To gather more insight in muscle contractile function in HCD-enhanced muscles, the effect of carnosine and beta-alanine supplementation on twitch and tetanus characteristics, force-frequency relation, and fatigability during isolated muscle contractions was also examined.
The main way that beta-alanine works is by reducing fatigability, mainly in muscles with a high proportion of fast-twitch muscle fibers, by buffering acidosis. What does buffering H+ have to do with anything? It has everything to do with everything. Well, almost. H+ is a byproduct of muscle contraction from the breakdown of ATP (adenosine triphosphate) – the cellular fuel that powers muscles. This training-induced increase in H+ is called metabolic acidosis. The more H+ that is generated, the more the pH level in your muscles fall (becomes acid). When this happens muscles, start to burn, and rapid exhaustion occurs stopping muscle contraction ability dead in its tracks. It’s this generation of H+ that forces you to stop a set – it causes muscle failure. And this H+ is generated from the muscle contractions that are required to do the reps in the set.
Another potential benefit of increased carnosine levels in muscle is improved calcium handling during muscle contraction.
In this research, mice were supplemented with either carnosine (0.1%, 0.5%, and 1.8%) or beta-alanine (0.6% and 1.2%) for 8-12 weeks in their drinking water. It was hypothesized that enhanced carnosine levels would contribute to reduced fatigability, and a leftward shift of the force-frequency relation (improved calcium handling in muscle).
The Results . . .
Only supplementation with 1.8% carnosine and 1.2% beta-alanine resulted in markedly higher carnosine (+160%) and anserine levels (+46%) compared with control mice. Also, there was an increased fatigue resistance at the beginning of the fatigue protocol on muscle and a marked leftward shift of the force-frequency relation in muscle (10%-31% higher relative forces) with beta-alanine supplementation.
Important Points
- Beta-alanine is the rate-limiting precursor for carnosine synthesis.
- The increase in carnosine levels is dependent on the total amount of ingested beta-alanine.
- First study to show improved calcium handling by a nutritional intervention.
- Beta-alanine supplementation improved fatigue resistance.
Bottom Line . . .
Beta-alanine supplementation resulted in a leftward shift of the force-frequency relation, predominantly in muscle characterized by fast-twitch fibers. Also, beta-alanine supplementation attenuated fatigue.
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References:
1. Sale C, Saunders B, Harris RC. Effect of beta-alanine supplementation on muscle carnosine concentrations and exercise performance. Amino Acids 2010;39:321-33.
2. Harris RC, Tallon MJ, Dunnett M, et al. The absorption of orally supplied beta-alanine and its effect on muscle carnosine synthesis in human vastus lateralis. Amino Acids 2006;30:279-89.
3. Hobson RM, Saunders B, Ball G, Harris RC, Sale C. Effects of beta-alanine supplementation on exercise performance: a meta-analysis. Amino Acids 2012;43:25-37.
4. Everaert I, Stegen S, Vanheel B, Taes Y, Derave W. Effect of beta-alanine and carnosine supplementation on muscle contractility in mice. Med Sci Sports Exerc 2013;45:43-51.
