Comparison of sustained-release and rapid-release ß-alanine formulations on changes in skeletal muscle carnosine and histidine content and isometric performance following a muscle-damaging protocol.

ß-alanine supplementation increases muscle carnosine content and improves anaerobic exercise performance by enhancing intracellular buffering capacity. ß-alanine ingestion in its traditional rapid-release formulation (RR) is associated with the symptoms of paresthesia. A sustained-release formulation (SR) of ß-alanine has been shown to circumvent paresthesia and extend the period of supply to muscle for carnosine synthesis. The purpose of this investigation was to compare 28 days of SR and RR formulations of ß-alanine (6 g day-1) on changes in carnosine content of the vastus lateralis and muscle fatigue. Thirty-nine recreationally active men and women were assigned to one of the three groups: SR, RR, or placebo (PLA). Participants supplementing with SR and RR formulations increased muscle carnosine content by 50.1% (3.87 mmol kg-1ww) and 37.9% (2.62 mmol kg-1ww), respectively. The change in muscle carnosine content in participants consuming SR was significantly different (p = 0.010) from those consuming PLA, but no significant difference was noted between RR and PLA (p = 0.077). Although participants ingesting SR experienced a 16.4% greater increase in muscle carnosine than RR, fatigue during maximal voluntary isometric contractions was significantly attenuated in both SR and RR compared to PLA (p = 0.002 and 0.024, respectively). Symptoms of paresthesia were significantly more frequent in RR compared to SR, the latter of which did not differ from PLA. Results of this study demonstrated that only participants consuming the SR formulation experienced a significant increase in muscle carnosine. Differences in the muscle carnosine response between these formulations may have practical significance for athletic populations in which small changes may have important implications on performance.

A kinetic model of carnosine synthesis in human skeletal muscle.

Drawing on previously published data, a mathematical model is proposed to describe the synthesis of carnosine in muscle using a slow release ß-alanine supplement (SR-CarnoSyn®). The model pre-supposes that the rate of synthesis for any given dose of ß-alanine (within the range 1.6-6.4 g day-1) is constant with time, but is first order with respect to daily ß-alanine dose. Simultaneously with synthesis, decay in carnosine is also assumed to be occurring, the rate in this case being a function of the concentration of carnosine. Decay in carnosine appears describable by first-order kinetics. By integration of the two rate reactions, a single mathematical equation was derived to describe the synthesis of carnosine and which closely fitted the experimental data over 56 days. The model, if validated by additional studies, could be used to compliment empirical observations of the changes in carnosine in muscle with supplementation, and allow objective examination of a number of possible influences affecting the rate constants of synthesis and decay.