The effect of 4 weeks β-alanine supplementation and isokinetic training on carnosine concentrations in type I and II human skeletal muscle fibres

Abstract

Seven male students were supplemented with beta-alanine (beta-ALG) for 4 weeks (6.4 g day(-1)) and seven with a matching placebo (PLG). Subjects undertook 4 weeks of isokinetic training with the right leg (T) whilst the left leg was untrained (UT), serving as a control. Each training session consisted of 10 x 10 maximal 90 degrees extension and flexion contractions at 180 degrees /s using a Kin-Com isokinetic dynamometer, with 1 min rest between bouts. Muscle biopsies were taken from the vastus lateralis immediately before and at the end of the supplementation period. Following freeze drying muscle fibres were dissected and characterised by their MHC profile, as type I, IIa, IIx, or as hybrids of these. Carnosine was measured by HPLC. There was a significant increase in carnosine in both T and UT legs of the beta-ALG (9.63 +/- 3.92 mmol kg(-1) dry muscle and 6.55 +/- 2.36 mmol kg(-1) dry muscle respectively). There was a significant increase in the carnosine content of all fibre phentotypes, with no significant difference between types. There were no significant differences in the changes in muscle or in fibres between the T and UT legs. In contrast there was no significant change in the carnosine content in either the T or UT legs with placebo. The results indicate that 4 weeks training has no effect on the muscle carnosine content. Whilst an increase was seen with beta-alanine supplementation, this was not further influenced by training. These findings suggest that beta-alanine availability is the main factor regulating muscle carnosine synthesis.

Muscle Carnosine Metabolism and β-Alanine Supplementation in Relation to Exercise and Training

“…Nevertheless, it should be mentioned that training can stimulate the responsiveness to creatine supplementation [113;114], which is not the case with carnosine loading [58].…”

Effects of Beta-Alanine Supplementation on Sprint Endurance

“…Since beta-alanine is considered the rate limiting substrate for carnosine production in the muscle, many studies have examined the efficacy of beta-alanine supplementation to increase intramuscular carnosine levels (1,11,15,20). Hill et al (15) examined the influence of beta-alanine supplementation on skeletal muscle carnosine concentrations.…”

β–alanine: performance effects, usage and side effects

“…In horses and camel gluteus medius muscle, the ratio in M-Carn of type I/II is 5 and 2.3 respectively [50,74]. In humans, using HPLC-based single fibre analysis the ratio is 1.3 to 2.0 [60,[71][72][73]. Muscles with a greater ratio of type II fibres have a greater M-Carn content than muscles which have the majority of type I fibres.…”

“…The gender differences in M-Carn during puberty may be explained by the larger cross sectional area of type II fibres present in males versus females [69,70]. Type II fibres in humans have 30 -100% greater levels of M-Carn than type I fibres [71][72][73]. When the M-Carn levels of type I and II fibres were compared by Tallon et al [60], no differences were found between males and females aged 20 -35 years.…”

“…Hill et al [72], and Kendrick et al [73,79] supplemented with 4 -6.4 g·day -1 for 10 weeks, 6.4 g·day -1 for 10 weeks and 6.4…”