Table 2. Study characteristics of studies investigating the combined direct effect of β-alanine and sodium bicarbonate supplementation on power-based exercise performance Reference Bellinger et al.40 Subjects 14 highlytrained male cyclists Design Double-blind, randomized, placebo-controlled for BA (BA, n = 7; PL, n = 7); randomized, cross-over design for SB (BA+SB, n = 7; BA+PL, n = 7; PL+SB, n = 7; PL+PL, n = 7) Hobson et al.43 20 trained rowers (club level) Double-blind, randomized, placebo-controlled for BA (BA, n = 10; PL, n = 10); double-blind, randomized, cross-over design for SB (BA+SB, n = 10; BA+PL, n = 10; PL+SB, n = 10; PL+PL, n = 10) de Salles Painelli et al.37 14 welltrained swimmers (males and females, state level) Double-blind, randomized, placebo-controlled design for BA (BA, n = 7; PL, n = 7); randomized, cross-over design for SB (BA+SB, n = 7; BA+PL, n = 7; PL+SB, n = 7; PL+PL, n = 7) Dosage protocol 28 d, 65 mg·kg-1 BM·d-1 (4 doses) BA or placebo (dextrose monohydrate); after 4 wk acute 0.3 g·kg-1 BM·d-1 placebo (dextrose) Exercise protocol 4-min cycling time trial (familiarization, pre, post 1, post 2, 2-4 days in between post 1 and post 2) (6 doses) SB or Result(s) Δ-values compared to PL+PL. Average power output (W), BA+SB 14.29 ± 11.40 W, 81% LBP; BA+PL 5.05 ± 8.42, 32%; PL+SB 13.53 ± 8.12, 87% LBP. Total work done, BA+SB 69%, BA+PL 27%, PL+SB 72% LBP. 30 d, 6.4 g·d-1 (4 doses of 2 × 800 mg tablets, 3-4 hr. intervals) BA or placebo (maltodextrin); after 4 wk acute 0.3 g·kg-1 BM·d-1 (2 doses) SB or placebo (dextrose) 2000-m rowing ergometer test (pre, post 1 (28 d), post 2 (30 d)) Δ; BA+SB, 0.3 ± 0.48%, 64% possible chance of benefit (compared to BA+PL); BA+PL, 1.5 ± 1.9%, 96% very likely chance of benefit; PL+SB, 0.8 ± 0.9%, 87% likely chance of benefit 4 wk, 3.2 g·d-1 during week 1 (4 doses), 6.4 g·d-1 (4 doses) BA or placebo (dextrose); after 4 wk acute 0.3 g·kg-1 BM·d-1 SB or placebo (dextrose) during week 2-4 100-m and 200-m freestyle swimming trials (pre, post 1, post 2, 4 days in between post 1 and post 2) 100-m, p = 0.14 (absolute change scores in the 4 conditions); absolute Δ, BA+SB -2.8%, BA+PL -1.4%, PL+SB -2.6%, PL+PL 1.1%. 200-m, p = 0.001 (absolute change scores; absolute Δ, BA+SB -2.13%, BA+PL -1.5%, PL+SB -2.3%, PL+PL 0.9%) BA, β-alanine; PL, placebo; SB, sodium bicarbonate; BM, body mass; LBP, likelihood of being positive. Side effects 2 of the 7 reported mild symptoms of paraesthesia related to BA; 3 of the 14 reported mild gastrointestinal symptoms related to SB No symptoms related to BA; 1 subject reported severe gastrointestinal symptoms related to SB 4 of the 7 reported mild symptoms of paraesthesia related to BA; all subjects experienced eructation with SB a plasma nitrite, a biomarker of NO availability, increase exceeding 30% following nitrate supplementation; n = 5) improved their performance with 2.0% (p < 0.05) and two out of the three non-responders did not improve their performance.56 The existence of responders and non-responders to nitrate supplementation is supported by the findings of Christensen et al.53 A positive group mean effect of nitrate supplementation on plasma nitrate + nitrite concentration was found (p < 0.01), without a significant group mean effect on time trial performance in well-trained subjects and professional athletes. However, two subjects that were classified as responders by Christensen et al.53 a 2.5 and 8% improvement in time trial performance. Future research is necessary to elucidate the reasons for the existence of responders (~20-25%)57 showed and non-responders and the reduced ergogenic effect of nitrate supplementation in well-trained subjects and professional athletes. It must be mentioned that in addition to differences in trainummer 3 | november 2015 | Sport & Geneeskunde 13 Pagina 12
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