title: β-Alanine supplementation enhances human skeletal muscle relaxation speed but not force production capacity.
abstract: β-Alanine (BA) supplementation improves human exercise performance. One possible explanation for this is an enhancement of muscle contractile properties, occurring via elevated intramuscular carnosine resulting in improved calcium sensitivity and handling. This study investigated the effect of BA supplementation on in vivo contractile properties and voluntary neuromuscular performance. Twenty-three men completed two experimental sessions, pre- and post-28 days supplementation with 6.4 g/day of BA (n = 12) or placebo (PLA; n = 11). During each session, force was recorded during a series of knee extensor contractions: resting and potentiated twitches and octet (8 pulses, 300 Hz) contractions elicited via femoral nerve stimulation; tetanic contractions (1 s, 1-100 Hz) via superficial muscle stimulation; and maximum and explosive voluntary contractions. BA supplementation had no effect on the force-frequency relationship, or the force responses (force at 25 and 50 ms from onset, peak force) of resting or potentiated twitches, and octet contractions (P > 0.05). Resting and potentiated twitch electromechanical delay and time-to-peak tension were unaffected by BA supplementation (P > 0.05), although half-relaxation time declined by 7-12% (P < 0.05). Maximum and explosive voluntary forces were unchanged after BA supplementation. BA supplementation had no effect on evoked force responses, implying that altered calcium sensitivity and/or release are not the mechanisms by which BA supplementation influences exercise performance. The reduced half-relaxation time with BA supplementation might, however, be explained by enhanced reuptake of calcium, which has implications for the efficiency of muscle contraction following BA supplementation.
authors.affiliation: Sport, Health and Performance Enhancement (SHAPE) Research Group, School of Science and Technology, Nottingham Trent University, United Kingdom;
authors.forename: Ricci
authors.initials: R
authors.lastname: Hannah
authors.affiliation: Sport, Health and Performance Enhancement (SHAPE) Research Group, School of Science and Technology, Nottingham Trent University, United Kingdom;
authors.forename: Rebecca Louise
authors.initials: RL
authors.lastname: Stannard
authors.affiliation: Sport, Health and Performance Enhancement (SHAPE) Research Group, School of Science and Technology, Nottingham Trent University, United Kingdom;
authors.forename: Claire
authors.initials: C
authors.lastname: Minshull
authors.affiliation: Laboratory of Applied Nutrition and Metabolism, School of Physical Education, University of São Paulo, São Paulo, Brazil; and.
authors.forename: Guilherme Giannini
authors.initials: GG
authors.lastname: Artioli
authors.affiliation: Junipa, Limited, Newmarket, Suffolk, United Kingdom.
authors.forename: Roger Charles
authors.initials: RC
authors.lastname: Harris
authors.affiliation: Sport, Health and Performance Enhancement (SHAPE) Research Group, School of Science and Technology, Nottingham Trent University, United Kingdom; craig.sale@ntu.ac.uk.
authors.forename: Craig
authors.initials: C
authors.lastname: Sale
mesh_terms: D000328:Adult; D002118:Calcium / Q000378:metabolism; D019587:Dietary Supplements; D004311:Double-Blind Method; D004558:Electric Stimulation / Q000379:methods; D004576:Electromyography / Q000379:methods; D015444:Exercise / Q000502:physiology; D006801:Humans; D007537:Isometric Contraction / Q000187:drug effects / Q000502:physiology; D007717:Knee / Q000502:physiology; D007719:Knee Joint / Q000187:drug effects / Q000378:metabolism / Q000502:physiology; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects / Q000502:physiology; D018763:Muscle Fatigue / Q000187:drug effects / Q000502:physiology; D009126:Muscle Relaxation / Q000187:drug effects* / Q000502:physiology*; D018482:Muscle, Skeletal / Q000187:drug effects* / Q000378:metabolism / Q000502:physiology*; D012146:Rest / Q000502:physiology; D015091:beta-Alanine / Q000008:administration & dosage*
chemical_list: D015091:beta-Alanine; D002118:Calcium
keywords: electrical stimulation; force-frequency relationship; muscle contractile properties; β-alanine