Aim: 

We aimed to compare the rate of carnosine synthesis in 3 lower leg muscles during b-alanine supplementation. Furthermore, we explored the rate of carnosine elimination from muscle upon cessation of supplementation. Finally, we compared carnosine content with isometric endurance in dorsiflexors.

Methods: 

20 untrained males participated in a placebo-controlled double-blind study and were supplemented for 5–6 weeks with either 4.8g/day b-alanine or placebo. Muscle carnosine was quantified in soleus, gastrocnemius and tibialis anterior by proton MRS before and after supplementation and 3 and 9 weeks into washout. Performance was evaluated by the time to exhaustion of isometric contraction at 45% MVC of the tibialis anterior.

Results: 

b-alanine supplementation significantly increased carnosine content on average by 29%. No difference in absolute increase was observed between muscle types. The time to exhaustion was not affected by the increase in carnosine content. After a washout period of 3 weeks, only 30% of the increase in carnosine content had disappeared. The carnosine content of the 3 lower leg muscles returned to their initial levels after a washout of 9 weeks.

Conclusions: 

b-alanine supplementation elevates muscle carnosine content to the same extent in oxidative and glycolytic muscles. Carnosine-loaded tibialis muscles do not exhibit improved isometric endurance. Muscle carnosine unloading takes 2–3 times longer than loading.