Dietary intake and stress fractures among elite male combat recruits

Background

We examined the effect of four weeks of ??-alanine supplementation on isometric endurance of the knee extensors at 45% maximal voluntary isometric contraction (MVIC).

Methods

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 ??-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.

Results

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 ??-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.

Conclusion

Four weeks of ??-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.