Overzichtsartikel 1:06.42 and 1:12.58 in men and women, respectively.5 The percentage performance enhancement, due to sodium bicarbonate supplementation, increases by 0.5% when the dosage increases by 1.0 mmol·kg-1 body mass and reduces by 0.6% when the duration of the event increases to 10 min or longer.20 It is hypothesized that combining an increase in intracellular and extracellular buffering capacity results in an augmented ergogenic effect, compared to increasing only one of the two. Recently, there are a few studies published on the effect of combining chronic β-alanine supplementation with acute sodium bicarbonate supplementation on performance (Table 2). The results of these studies showed that the additive effect of acute sodium bicarbonate supplementation to chronic β-alanine supplementation ranged from minimal 40 to a 64% possible chance of benefit.43 Although there are only a few studies that investigated the effect of combining β-alanine with sodium bicarbonate supplementation on performance in trained and highly-trained athletes and more research is necessary, it seems that there might be an additive effect of combining these supplements in power-based sport events. Like β-alanine supplementation sodium bicarbonate supplementation might result in side effects.40,46 ticipated in the study of Bellinger et al.40 Three of the 14 subjects that parexperienced mild gastrointestinal symptoms related to sodium bicarbonate supplementation. While acute supplementation with sodium bicarbontate has been studied most extensively, a recent study of Mc Naughton and Thompson47 showed that chronic supplementation might be preferable. One day after acute supplementation with sodium bicarbonate the ergogenic effect on performance was already absent, but one and two days after chronic (6 days) supplementation the ergogenic effect was still present. Thus, subjects using the chronic protocol can eliminate the chance on side effects during competition by stopping supplementation on the day(s) of competition. Another possibility to minimize the chance on gastrointestinal discomfort after sodium bicarbonate ingestion is to co-ingest a small carbohydrate-rich meal.46 Supplementation with sodium bicarbonate might not only result in gastrointestinal discomfort but might also result in a 1-2% increase in body mass.15 However, weight bearing sports, like running were included in the meta-analysis of Carr et al.20 and still a performance enhancement of 1.7% was found. Mc Naughton and Thompson47 studied the direct effect of chronic supplementation on performance. However, there are also a few studies48,49 12 Sport & Geneeskunde | november 2015 | nummer 3 that evaluated the indirect effect of chronic sodium bicarbonate supplementation on performance. Driller et al.49 showed, using a double-blind placebocontrolled trial, that during a four-week training period, including two high-intensity interval-training sessions per week, sodium bicarbonate supplementation did not result in significant additional benefits to 2000-m rowing performance in highly trained rowers. This in contrast to the finding of Edge et al.,48 they showed significant greater improvements in time-to-fatigue tests after an eight-week period of combined high-intensity interval training and sodium bicarbonate supplementation in recreationally trained subjects. This discrepancy might be due to difference in training status of the subjects, the duration of the training period or the difference in ‘performance’ test. Future research is necessary to elucidate the indirect effect of chronic sodium bicarbonate supplementation on performance. To summarize, the reviewed literature showed that acute sodium bicarbonate supplementation results in a moderate performance enhancement for exercise bouts lasting between 1 and 10 min. In addition, there might be additive effect of combining chronic β-alanine and acute sodium bicarbonate supplementation on performance. Future research is necessary to elucidate the indirect effect of chronic sodium bicarbonate supplementation on long-track speed-skating performance. Nitrate The first study investigating the effect of acute dietary nitrate supplementation on exercise performance showed that cycling time trial performance (4 to 16.1 km) improved by 2.7 to 2.8% in trained50 cyclists.51 However, recent investigations in well-trained and professional athletes showed no significant effect of 6-8 days of dietary nitrate supplementation on performance bouts lasting ~4 to 19 min.52,53 These conflicting findings might be caused by an interaction between training status and the possible beneficial effect of dietary nitrate supplementation.54,55 It seems that the ergogenic effect of dietary nitrate supplementation is less in well-trained or highly-trained subjects and professional athletes, compared to untrained and moderatelytrained or recreationally active subjects.55 When looking at the individual effects instead of the group mean effects, Wilkerson et al.56 noted that within a group of trained and well-trained cyclists there seem to be responders and non-responders to nitrate supplementation. In their study, dietary nitrate supplementation resulted in a non-significant group mean performance improvement of 0.8%. However, the responders (defined as subjects with Pagina 11
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