β-alanine supplementation improves in-vivo fresh and fatigued skeletal muscle relaxation speed

Abstract

Purpose: In fresh muscle, supplementation with the rate-limiting precursor of carnosine, β-alanine (BA), results in a decline in muscle half-relaxation time (HRT) potentially via alterations to calcium (Ca2+) handling. Accumulation of hydrogen cation (H+) has been shown to impact Ca2+ signalling during muscular contraction, carnosine has the potential to serve as a cytoplasmic regulator of Ca2+ and H+ coupling, since it binds to both ions. The present study examined the effect of BA supplementation on intrinsic in-vivo isometric knee extensor force production and muscle contractility in both fresh and fatigued human skeletal muscle assessed during voluntary and electrically evoked (nerve and superficial muscle stimulation) contractions.

Methods: Twenty-three males completed two experimental sessions, pre- and post- 28 day supplementation with 6.4 g.day-1 of BA (n = 12) or placebo (PLA; n = 11). Isometric force was recorded during a series of voluntary and electrically evoked knee extensor contractions.

Results: BA supplementation had no effect on voluntary or electrically evoked isometric force production, or twitch electromechanical delay and time-to-peak tension. There was a significant decline in muscle HRT in fresh and fatigued muscle conditions during both resting (3 ± 13%; 19 ± 26%) and potentiated (1 ± 15%; 2 ± 20%) twitch contractions.

Conclusions: The mechanism for reduced HRT in fresh and fatigued skeletal muscle following BA supplementation is unclear. Due to the importance of muscle relaxation on total energy consumption, especially during short, repeated contractions, BA supplementation may prove to be beneficial in minimising contractile slowing induced by fatigue.

Trial registration: The trial is registered with Clinicaltrials.gov, ID number NCT02819505.

Keywords: Carnosine; Contractile properties; Electrical stimulation; Muscle fatigue.

Conflict of interest statement

This study was funded by and completed at Nottingham Trent University. The β-alanine and maltodextrin supplements for this study were provided free of charge from Natural Alternatives International (San Marcos, California), although no additional funding was provided. Roger Harris is an independent paid consultant of NAI and is named as an inventor on patents held by NAI.

Figures

Fig. 1

Electrically evoked half-relaxation time of β-alanine (BA) and placebo (PLA) groups pre- and post-supplementation, in fresh and fatigued muscle during: resting twitch (a), potentiated twitch (b), and octets (c). Data are means ± 1SD. **P ≤ 0.01 and *P ≤ 0.05 for post hoc independent t-test between BA and PLA groups

Fig. 2

Representative records of the force response during an electrically evoked resting twitch contraction pre- and post-supplementation with β-alanine under fresh conditions. These records are averaged records from three participants to provide an illustration of the decline in twitch half-relaxation time

Fig. 3

Explosive and maximal voluntary isometric force (MVIF) responses (a), and agonist EMG normalized to M-wave area (Mmax) during explosive contractions (0–50, 50–100, and 100–150 ms from onset) and at MVIF (b) for the BA and PLA groups pre- and post-supplementation, in fresh and fatigued muscles. Data are means ± 1SD

Fig. 4

Force–EMG relationship measured during submaximal voluntary contractions (15–90% MVIF) for the BA and PLA groups pre- and post-supplementation, in fresh and fatigued muscles. Data are means ± 1SD