1 Muscle carnosine loading through chronic oral beta--alanine supplementation has been shown to be 2 effective for short--duration, high--intensity exercise. This randomised, placebo controlled study 3 explored whether the ergogenic effect of beta--alanine supplementation is also present for longer 4 duration exercise. Subjects (27 well--trained cyclists/triathletes) were supplemented with either 5 beta--alanine or placebo (6.4 g/day) for six weeks. Time to completion and physiological

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... for 6 a 1--h cycling time--trial were compared between pre--and post--supplementation. Muscle carnosine 7 concentration was also assessed via proton magnetic resonance spectroscopy before and after 8 supplementation. Following beta--alanine supplementation, muscle carnosine concentration was 9 increased by 143 ± 151% (mean ± SD; p < 0.001) in the gastrocnemius and 161 ± 56% (p < 0.001) in 10 the soleus. Post--supplementation time trial performance was significantly slower in the placebo 11 group (60.6 ± 4.4 to 63.0 ± 5.4 min; p < 0.01) and trended towards a slower performance following 12 beta--alanine supplementation (59.8 ± 2.8 to 61.7 ± 3.0 min; p = 0.069). We found an increase in 13 lactate/proton concentration ratio following beta--alanine supplementation during the time--trial 14 (209.0 ± 44.0 (beta--alanine) vs. 161.9 ± 54.4 (placebo); p < 0.05), indicating that a similar lactate 15 concentration was accompanied by a lower degree of systemic acidosis, even though this acidosis 16 was quite moderate (pH ranging from 7.30--7.40). In conclusion, chronic beta--alanine 17 supplementation in well--trained cyclists had a very pronounced effect on muscle carnosine 18 concentration and a moderate attenuating effect on the acidosis associated with lactate 19 accumulation, yet without affecting 1--h time--trial performance under laboratory conditions. 20 Keywords: beta--alanine, supplement, exercise, buffering, magnetic resonance spectroscopy 21 22 23 24