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Muscle Fatigue

Continuing studies prove that beta-alanine is the real deal as far as enhancing training effectiveness is concerned. When researchers examined its effects in 400-meter sprinters, they already knew that highly trained anaerobic athletes have higher levels of carnosine, of which beta-alanine is the intramuscular precursor. The sprinters in the new study were world class, so if any athletes were likely to have higher-than-normal muscle carnosine, they’d be the ones.

Fifteen male athletes got either 4.8 grams a day of beta-alanine or a placebo. Their muscle carnosine was measured by a new, noninvasive technique called proton magnetic resonance spectroscopy (say it fast five times!) that does away with the painful muscle biopsies previously used for that purpose. Their performance was judged by isokinetic testing—five bouts of 30 maximum voluntary knee extensions. Other tests involved isometric muscle contractions and indoor 400-meter running time, which was probably the most important to the athletes themselves.

Although as high-level athletes they already had greater-than-normal muscle carnosine, beta-alanine supplementation increased the carnosine in both the soleus (47 percent) and the gastrocnemius (37 percent). Those in the placebo group showed stable carnosine in the soleus, while the content in the gastrocnemius rose by 16 percent through exercise alone. Dynamic knee extension torque during the fourth and fifth bouts was significantly improved in the beta-alanine group but not in the placebo group. 

From a bodybuilding standpoint, the study suggests that maximum effects of beta-alanine would occur during later sets. That makes sense, since the mechanism of beta-alanine increases muscle carnosine, and carnosine is a major intramuscular buffer that neutralizes the excess acid produced by muscle fatigue. Naturally, you would be more prone to that effect during later sets.

Isometric endurance and 400-meter race time weren’t affected by beta-alanine. The authors suggest that may have occurred because the buildup of muscle acidity isn’t extensive enough in that race to limit muscle performance. Still, the top-level sprinters had increased muscle carnosine after taking beta-alanine. The implication is that there’s no ceiling on using beta-alanine as there is with creatine. Simply put, no matter how great an athlete or bodybuilder you are, there’s always room for more carnosine in your muscles. In contrast, once muscles are filled with creatine, any excess is simply excreted from the body. IM


Derave, W., et al. (2007). Beta-alanine supplementation augments muscle carnosine content and attenuates fatigue during repeated isokinetic contraction bouts in trained sprinters. J Appl Physiol. In press.

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