When muscles work hard, they build up waste products like lactic acid. Excess lactic acid is one of the factors that cause muscle fatigue. When this lactic acid buildup is neutralized, the muscle can contract more effectively, and endurance is improved.
The amino acid carnosine is the best lactic acid buffer. Supplementing with carnosine is not effective though, because it is broken down in the GI tract, which means it does not reach the muscle. Lucky for us, carnosine is formed from beta-alanine.
Thus, beta-alanine leads to improvements in muscle endurance and exercise capacity. Specifically, it improves the anaerobic threshold and time to exhaustion.
For Muscle Growth:
Beta-Alanine helps you train harder and longer by allowing you to increase the intensity of your workouts thru greater anaerobic capacity.
Increased training volume results in greater time seen under tension, and thus more muscle growth.