variability can prevent important effects from being statistically significant. The effect of chronic β-alanine supplementation on middledistance power-based events, namely 400-m and 800-m running races, was investigated by Derave et al.35 al.36 and Ducker et These 400-m and 800-m races resulted in finish times ranging from ~49 s to ~2.5 min, which corresponds best with 1000m and 1500-m speed-skating events. β-alanine supplementation did not significantly improve 400-m running performance,35 but did result in a significantly larger performance enhancement than placebo ingestion before a 800-m race (Table 1).36 In addition, de Salles Painelli et al.37 studied the effect of β-alanine supplementation on 100-m and 200-m swimming events, also similar in duration to 1000-m and 1500-m speedskating events. The authors concluded that β-alanine supplementation resulted in a non-significant improvement of the 100 m and a significant improvement of 200-m swimming performance. The cause of the non-significant effect of β-alanine supplementation on 100-m swimming and 400-m running performances might be due to the short duration of these events. Hobson et al.38 concluded, based on a metaanalysis that exercise of a duration < 60 s, like a 500 m skating, is not improved by β-alanine supplementation. A 4-min cycling time trial can also be regarded as a powerbased sporting event and the duration corresponds best with a 3000-m speed-skating event. β-alanine supplementation resulted in a 3239 on average power output,40 to 44% possible chance of benefit compared to a placebo (Table 1). Both studies reported that the likelihood of a negative effect was 1%, which results in a 67 and 55% chance on a trivial effect. Finally, rowing can just as middle-distance running, track cycling, and speed skating be regarded as a power-based sport.15 similar in terms of duration to a 5000-m speed-skating event. The effect of β-alanine supplementation on 2000-m rowing performance ranged from a non-significant difference between the β-alanine and placebo group41,42 very likely chance of benefit43 (Table 1). What strikes when looking at the results summarized in Table 1, is that the studies reporting a significant effect and a very likely chance of benefit are the two studies which included club-level athletes instead of highly-trained athletes or athletes of national and/or international level. However, as not all studies reported the training background of their subjects, it remains doubtful to conclude that the subjects in the studies of Ducker et al.36 and Hobson et al.43 were indeed less well trained than the subjects in the other Sodium bicarbonate Based on 38 studies, using mainly a double-blind design, Carr et al.20 tion by male athletes, using a dosage of 3.5 mmol·kg-1 mass (~0.3 g·kg-1 found that sodium bicarbonate supplementabody body mass) ingested prior to a 1-min sprint, enhanced performance by 1.7% (± 90% CI, 2.0%), which can be regarded as a moderate performance enhancement. A 1-min sprint corresponds in duration best to a 1000-m speed-skating race, with a current world record of nummer 3 | november 2015 | Sport & Geneeskunde 11 studies summarized in Table 1. Besides, in the study of de Salles Painelli et al.,44 in which the influence of training status on the efficacy of β-alanine supplementation on repeated Wingate performances was determined, a significant ergogenic effect of β-alanine was found, regardless of training status (non-trained or trained). It therefore seems that the effect of training status on the efficacy of β-alanine supplementation is negligible. So, in general the effect of β-alanine supplementation on power-based sports ranges from no significant effect to a very likely chance of benefit (Table 1). It must be mentioned that 6 out of 8 studies described in Table 1, used a doubleblind, randomized, placebo-controlled design, which is preferable over a single-blind design. Unfortunately, the effect of β-alanine supplementation on performance in these studies is also inconclusive. The inconclusive results might be partly due to the high interindividual variation in the increase in carnosine content with β-alanine supplementation.35,42 with supplementation was independent of the initial carnosine content in a group of well-trained sprinters,35 but the increase in muscle carnosine content is positively correlated (r = 0.50, p = 0.042) to performance improvement.42 Thus, the effect of β-alanine supplementation on performance might vary substantially between individuals and seems to depend on the increase in muscle carnosine content. Further research is necessary to find the cause of the high interindividual variation and to study the effect of β-alanine supplementation in elite athletes on long-track speed-skating events. When athletes want to experiment with β-alanine supplementation, they should be careful when choosing a certain dose. Supplementing β-alanine in acute doses above 10 mg·kg-1 The 2000-m rowing event, lasting about 5-8 min is in an increased incidence of paraesthesia.19 body mass (or 800 mg) results These adverse to a effects can be minimized or avoided by limiting the amount of β-alanine ingested per dose (increasing the frequency of intake over the day)19 β-alanine formula.45 or by choosing a slow-release The increase in muscle carnosine content Pagina 10
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Sport & Geneeskunde nummer 3 | november 2015 Lees publicatie 52Home