Abstract
Backgroundβ-alanine supplementation has been shown to improve high-intensity exercise performance and capacity. However, the effects on intermittent exercise are less clear, with no effect shown on repeated sprint activity. The aim of this study was to investigate the effects of β-alanine supplementation on YoYo Intermittent Recovery Test Level 2 (YoYo IR2) performance.MethodsSeventeen amateur footballers were allocated to either a placebo (PLA; N = 8) or β-alanine (BA; N = 9) supplementation group, and performed the YoYo IR2 on two separate occasions, pre and post 12 weeks of supplementation during a competitive season. Specifically, players were supplemented from early to mid-season (PLA: N = 5; BA: N = 6) or mid- to the end of the season (PLA: N = 3; BA: N = 3). Data were analysed using a two factor ANOVA with Tukey post-hoc analyses.ResultsPre supplementation scores were 1185 ± 216 and 1093 ± 148 m for PLA and BA, with no differences between groups (P = 0.41). YoYo performance was significantly improved for BA (+34.3%, P ≤ 0.001) but not PLA (−7.3%, P = 0.24) following supplementation. 2 of 8 (Early – Mid: 2 of 5; Mid – End: 0 of 3) players improved their YoYo scores in PLA (Range: -37.5 to + 14.7%) and 8 of 9 (Early – Mid: 6 of 6; Mid – End: 2 of 3) improved for BA (Range: +0.0 to +72.7%).Conclusions12 weeks of β-alanine supplementation improved YoYo IR2 performance, likely due to an increased muscle buffering capacity resulting in an attenuation of the reduction in intracellular pH during high-intensity intermittent exercise.
Highlights
Carnosine (β-alanyl-L-histidine) is a naturally occurring dipeptide found in high concentrations in skeletal muscle [1] and due to its pKa (6.83), it is a suitable buffer over the exercise intramuscular pH transit-range [2]. β-alanine supplementation has been shown to be effective in increasing muscle carnosine levels [1], thereby increasing muscle buffering capacity, with the potential to improve exercise performance and capacity that is limited by the accumulation of hydrogen ions (H+) [3,4]
YoYo Intermittent Recovery Test performance is closely related to football match performance, since YoYo IR1 outcomes are correlated with high intensity running and total distance covered during a football match for top class referees [16] and footballers [13]
This is in contrast to previous research that has shown no effect of β-alanine on repeated sprint exercise [7,8,9], these studies used exercise protocols consisting of performance tests incorporating periods of high-intensity and sprint activity of less than 60 s in duration, which are suggested to be unaffected by β-alanine supplementation [10]
Summary
Carnosine (β-alanyl-L-histidine) is a naturally occurring dipeptide found in high concentrations in skeletal muscle [1] and due to its pKa (6.83), it is a suitable buffer over the exercise intramuscular pH transit-range [2]. β-alanine supplementation has been shown to be effective in increasing muscle carnosine levels [1], thereby increasing muscle buffering capacity, with the potential to improve exercise performance and capacity that is limited by the accumulation of hydrogen ions (H+) [3,4]. The YoYo Intermittent Recovery Tests (Level 1 [YoYo IR1] and 2 [YoYo IR2]) were designed [11] to evaluate the ability of an individual to repeatedly perform and recover from intense exercise, and are applicable to team sports players due to the specificity of the exercise undertaken [12]. These tests have been shown to be sensitive to training adaptations [13,14], seasonal variation [13] and differences in playing position and playing standard [13,15]. These findings suggest that the YoYo IR Tests are appropriate models for examining the effects of interventions designed to manipulate changes in individual performance during team sport exercise
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