β-alanine supplementation improves isometric endurance of the knee extensor muscles

Thirteen males (age 23？±？6 y; height 1.80？±？0.05？m; body mass 81.0？±？10.5？kg), matched for pre-supplementation isometric endurance, were allocated to either a placebo (n？=？6) or β-alanine (n？=？7; 6.4？g·d-1 over 4？weeks) supplementation group. Participants completed an isometric knee extension test (IKET) to fatigue, at an intensity of 45% MVIC, before and after supplementation. In addition, two habituation tests were completed in the week prior to the pre-supplementation test and a further practice test was completed in the week prior to the post-supplementation test. MVIC force, IKET hold-time, and impulse generated were recorded.IKET hold-time increased by 9.7？±？9.4？s (13.2%) and impulse by 3.7？±？1.3 kN·s-1 (13.9%) following β-alanine supplementation. These changes were significantly greater than those in the placebo group (IKET: t(11)？=？2.9, p ≤0.05; impulse: t(11)？=？3.1, p？≤？0.05). There were no significant changes in MVIC force in either group.Four weeks of β-alanine supplementation at 6.4？g·d-1 improved endurance capacity of the knee extensors at 45% MVIC, which most likely results from improved pH regulation within the muscle cell as a result of elevated muscle carnosine levels.