Beta-alanine supplementation improves isometric, but not isotonic or isokinetic strength endurance in recreationally strength-trained young men

Abstract

β-Alanine (BA) supplementation may be ergogenic during high-intensity exercise, primarily due to the buffering of hydrogen cations, although the effects of beta-alanine supplementation on strength endurance are equivocal. The aim of the study was to determine the effects of 4 weeks of beta-alanine supplementation on skeletal muscle endurance using a battery of performance tests. This study employed a parallel group, repeated measures, randomised, double-blinded and placebo-controlled design. Twenty recreationally strength-trained healthy males completed tests of isotonic strength endurance (repeated bench and leg press), along with tests of isometric and isokinetic endurance conducted using an isokinetic dynamometer. Tests were performed before and after a 4 week intervention, comprising an intake of 6.4 g day of BA (n = 9) or placebo (maltodextrin, n = 11). Time-to-exhaustion during the isometric endurance test improved by ~ 17% in the BA group (p < 0.01), while PL remained unchanged. No significant within-group differences (p > 0.1) were shown for any of the performance variables in the isokinetic test (peak torque, fatigue index, total work) nor for the total number of repetitions performed in the isotonic endurance tests (leg or bench press). Four weeks of BA supplementation (6.4 g day) improved isometric, but not isokinetic or isotonic endurance performance.

Short-Time β-Alanine Supplementation on the Acute Strength Performance after High-Intensity Intermittent Exercise in Recreationally Trained Men

“…To our knowledge, this was the first study to investigate the interaction between β-alanine supplementation and resistance exercise performance during acute concurrent exercise. Our results are very similar to a study recently published by Bassinello et al [28]. In that study, resistance trained subjects were supplemented with 6.4 g/day of β-alanine during 28 days of non-structured resistance training.…”

“…We could not confirm this hypothesis, even though there was a tendency for greater increases in FFM in the β-alanine group (β-alanine = 2.8% versus placebo = 1.0%), post hoc testing did not reach statistical significance, and the effect size for the β-alanine group was small ( d = 0.30). These results support our contention that the ability of β-alanine supplementation enhance resistance training and thereby muscle hypertrophy is unclear, and agrees with the mixed results reported in the literature, as some [17,35], but not all [28,36] studies report greater improvements in lean mass.…”

“…In contrast, Outlaw et al [18] reported greater increases in leg press repetitions to failure following four and eight weeks of β-alanine supplementation. Differences in training status between Outlaw et al [18] (untrained collegiate women) and the current study and Bassinello et al [28] (resistance trained men) and the training period, as well as the supplementation period (eight weeks versus 28 days) may explain these discrepancies in results. Additionally, given that females tend to have less intramuscular carnosine concentrations when matched for aged and training status compared to males [29], gender differences may also influence the ergogenic effects of β-alanine supplementation.…”

“…As such, our primary hypothesis was that β-alanine would enhance resistance exercise performance when preceded by HIIE via enhanced H + buffering. Although we were unable to measure blood pH or H + concentrations, using a similar resistance exercise protocol, Bassinello et al [28] reported reductions in plasma pH (pH = 7.25 ± 0.03) following just two sets of leg press to failure with 2 min of rest between sets, without further reductions in pH occurring in sets four to eight. Therefore, it is likely that the exercise protocol used herein generated an intracellular metabolic environment whereby increased intramuscular carnosine should enhance performance via increased buffering.…”

“…In a second study, Hoffman et al [31] reported that β-alanine supplementation increased repetitions to fatigue during back squats with 70% 1 RM. This study utilized a repeated measures design; however, as discussed by Bassinello et al [28], the washout period was only four weeks, which was likely not sufficient to allow for carnosine concentrations to return to baseline [32].…”