Table 2.
Description of studies that have investigated the effects of dietary NO3− supplementation on high-intensity, sprint-type explosive efforts in humans. There were 4 studies out of 10 that observed significant performance improvements to sprints in cycling [44,49,59] and running [60]. Specifically, NO3− improved cycling Pmax [44], RPMopt [44], Pmean [49], and total work performed [59].
| Reference | Subjects | Supplementation | Exercise Protocol | Results |
|---|---|---|---|---|
| Buck et al. [61] | 13 female amateur basketball and soccer players | 6 d of BR supplementation (NO3− 6 mmol per day) | Before, during, and after 60 min in a simulated team-game: 6 × 20 m running sprints, 25 s rest | ↔ Best sprint time (set 1): −0.3% (3.68 ± 0.26 vs. 3.69 ± 0.25 s; d = 0.04 [−0.85 to 0.77]) ↔ Best sprint time (set 2): −0.8% (3.77 ± 0.32 vs. 3.80 ± 0.25 s; d = 0.11 [−0.91 to 0.71]) ↔ Best sprint time (set 3): +1.1% (3.81 ± 0.32 vs. 3.77 ± 0.25 s; d = 0.14 [−0.68 to 0.95]) |
| Rimer et al. [44] | 13 competitive athletes (female, n = 2, male, n = 11) | 2.5 h prior to exercise acute BR ingestion (NO3− 11.2 mmol) |
4 × 3 to 4 s cycling sprints, 2 min rest | ↑ Pmax: +6 ± 2.6 vs. 2 ± 3.8% (d = 1.21 [0.31 to 2.07]) ↑ RPMopt: +6.5 ± 11.4 vs. 0.3 ± 4.1% (d = 0.79 [−0.14 to 1.54]) |
| Smith et al. [62] | 12 male recreationally active athletes | 3 h prior to exercise acute BR ingestion (NO3− 6.2 mmol) |
20 × 6 s cycling sprints in temperate (22.5 °C) and hot environmental conditions (30 °C), 114 s rest | ↔ Ppeak (hot): −6.0% (659 ± 100 vs. 683 ± 139 W; d = 0.21 [−1.04 to 0.66]) ↔ Pmean (temperate): −1.6% (562 ± 120 vs. 571 ± 124 W; d = 0.08 [−0.92 to 0.78]) ↔ Pmean (hot): −5.9% (543 ± 29 vs. 575 ±39 W; d = 0.97 [−11.79 to −0.01]) ↔ Total work (temperate): −1.5% (67.44 ± 14.39 vs. 68.46 ± 15.07 kJ; d = 0.07 [−0.91 to 0.78]) ↔ Total work (hot): −5.6% (66.07 ± 10.84 vs. 69.74 ± 15.13 kJ; d = 0.03 [−1.12 to 0.58]) |
| Thompson et al. [59] | 16 male recreational team-sport players | 2.5 h prior to exercise and 7 d of BR supplementation (NO3− 12.8 mmol per day) |
2 × 40 min cycling sprints, 15 min rest 10 × 6 s sprints, 100 s rest at 35% VO2max + 14 s passive rest 5 × 4 s sprints, 16 s rest at 35% VO2max 10 × 6 s sprints, 100 s rest at 35% VO2max + 14 s passive rest |
↑ Total work: +3.5% (123 ± 19 vs. 119 ± 17 kJ; d = 0.23 [−0.51 to 0.94]) |
| Wylie et al. [49] | 10 male recreational team-sport players | 2.5 h prior to exercise and 3 to 5 d of BR supplementation (NO3− 8.2 mmol per day) |
24 × 6 s cycling sprints, 24 s rest | ↔ Ppeak (mean): +1.3% (792 ± 159 vs. 782 ± 154 W; d = 0.07 [−0.88 to 1.00]) ↑ Pmean (sprints 1–6): +7.3% (694 ± 125 vs. 647 ± 122 W; d = 0.39 [−0.58 to 1.31]) ↔ Pmean (sprints 7–12): +3.9% (560 ± 100 vs. 539 ± 112 W; d = 0.20 [−0.75 to 1.13]) ↔ Pmean (sprints 13–18): +5.3% (518 ± 111 vs. 492 ± 121 W; d = 0.23 [−0.73 to 1.16]) ↔ Pmean(sprints 19–24): +4.8% (500 ± 114 vs. 477 ± 119 W; d = 0.20 [−0.75 to 1.13]) ↑ Pmean (mean): +5.4% (568 ± 136 vs. 539 ± 136 W; d = 0.22 [−0.74 to 1.15]) |
| Kent et al. [63] | 12 male team sport players | 2 h prior to exercise acute BR ingestion (NO3− 13 mmol) | 4 sets of 9 × 4 s cycling sprints with 16 s active + 6 s passive rest, interspersed with 3 min rest (3000 m simulated altitude) | ↔ Ppeak (set 1): −2.4% (1185 ± 172 vs. 1214 ± 179 W; d = 0.17 [−1.01 to 0.69]) ↔ Ppeak (set 2): −1.0% (1157 ± 178 vs. 1181 ± 163 W; d = 0.15 [−0.98 to 0.71]) ↔ Ppeak (set 3): −0.5% (1159 ± 186 vs. 1165 ± 160 W; d = 0.04 [−0.88 to 0.81]) ↔ Ppeak (set 4): −1.0% (1152 ± 194 vs. 1164 ± 139 W; d = 0.07 [−0.92 to 0.78]) ↔ Pmean (set 1): −2.7% (807 ± 144 vs. 829 ± 144 W; d = 0.16 [−1.00 to 0.70]) ↔ Pmean (set 2): +3.1% (794 ± 156 vs. 770 ± 142 W; d = 0.17 [−0.69 to 1.00]) ↔ Pmean (set 3): +2.1% (809 ± 150 vs. 792 ± 131 W; d = 0.15 [−0.73 to 0.96]) ↔ Pmean (set 4): −1.0% (779 ± 156 vs. 804 ± 122 W; d = 0.19 [−1.02 to 0.68]) ↔ Total work (set 1): −2.7% (29.0 ± 5.18 vs. 29.8 ± 5.19 J; d = 0.16 [−1.00 to 0.70]) ↔ Total work (set 2): −0.5% (28.5 ± 5.61 vs. 28.7 ± 5.10 J; d = 0.04 [−0.88 to 0.81]) ↔ Total work (set 3): +2.5% (29.1 ± 5.38 vs. 28.4 ± 4.75 J; d = 0.14 [−0.71 to 0.98]) ↔ Total work (set 4): +0.2% (28.9 ± 5.62 vs. 28.9 ± 4.39 J; d = 0.00 [−0.85 to 0.85]) ↔ Work decrement (set 1): −47.1% (11.9 ± 6.9 vs. 17.5 ± 11.7%; d = 0.48 [−1.43 to 0.30]) ↔ Work decrement (set 2): −21.7% (12.9 ± 9.1 vs. 15.7 ± 14.5%; d = 0.47 [−1.07 to 0.63]) ↔ Work decrement (set 3): +4.5% (13.9 ± 8.4 vs. 13.3 ± 11%; d = 0.09 [−0.79 to 0.91]) ↔ Work decrement (set 4): +2.5% (12.2 ± 6.3 vs. 11.9 ± 7.1%; d = 0.05 [−0.80 to 0.89]) |
| Kokkinoplitis et al. [56] | 7 healthy males | 3 h prior to exercise acute BR ingestion (NO3− 6.45 mmol) | 5 × 6 s running sprints on treadmill, 30 s rest | ↔ Ppeak (mean): +4.9% (4133.5 ± 674.4 vs. 3938.3 ± 603.1 W; d = 0.33 [−0.89 to 1.46]) |
| Thompson et al. [60] | 36 team sport players | 2.5 h prior to exercise and 5 d of BR supplementation (12.8 mmol NO3− per day) |
5 × 20 m running sprints in running lanes, 30 s rest | ↓ Total time: −1.2% (3.98 ± 0.18 vs. 4.03 ± 0.19 s; d = 0.27 [−0.71 to 0.20]) ↓ Time (5 m): −2.3% (1.73 ± 0.09 vs. 1.77 ± 0.09 s; d = 0.45 [−0.92 to 0.04]) ↓ Time (10 m): −1.6% (2.53 ± 0.2 vs. 2.57 ± 0.12 s; d = 0.25 [−0.71 to 0.23]) ↓ Time (5–10 m): −1.2% (0.80 ± 0.04 vs. 0.81 ± 0.04 s; d = 0.25 [−0.72 to 0.22]) ↔ Time (10–20 m): −0.7% (1.45 ± 0.07 vs. 1.46 ± 0.09 s; d = 0.13 [−0.59 to 0.35]) |
| Clifford et al. [64] | 20 male team sport players | 4 d of BR supplementation (2.31 mmol NO3− per day) |
20 × 30 m sprints, 30 s rest | ↔ Best sprint time: BR −0.7% (4.38 ± 0.17 vs. 4.41 ± 0.23 s; d = 0.15 [−0.79 to 0.50]) and PL +1.1% (4.53 ± 0.15 vs. 4.48 ± 0.14 s; d = 0.35 [−0.31 to 0.98]). |
| López-Samanes et al. [57] | 13 trained male tennis players | 3 h prior to exercise of acute BR ingestion (6.4 mmol NO3−) | 5 tennis serves, 2 × 10 m sprints, 2 × agility test (5–0–5), 1 min rest | ↔ Serve speed: −2.7% (160.6 ± 10.4 vs. 165.0 ± 10.8 km/h; d = 0.15 [−1.22 to 0.42]) ↔ Best sprint time (10 m): +1.1% (1.86 ± 0.07 vs. 1.88 ± 0.05 s; d = 0.39 [−1.13 to 0.50]) ↔ Best sprint time (5–0–5): +2.0% (2.60 ± 0.10 vs. 2.64 ± 0.10 s; d = 0.69 [−1.21 to 0.43]) |
↑ = significant increase; ↓ = significant decrease; ↔ = no difference; BR = beetroot juice; n =sample size; NO3− = nitrate; PL = placebo; Pmax = maximal power; Pmean = mean power; Ppeak = peak power; RPMopt = maximal optimal pedaling rate; VO2max = maximal oxygen consumption; [ ] denotes confidence intervals.