Effects of acute beetroot juice intake on performance, maximal oxygen uptake, and ventilatory efficiency in well-trained master rowers: a randomized, double-blinded crossover study

Figures & data

Figure 1. CONSORT flowchart of randomized, double-blind, crossover design.

Abbreviations: BRJ = beetroot juice; PL = placebo

Figure 2. Experimental procedure of the rowing ergometer test.

Abbreviations: BRJ = beetroot juice; CPRT= cardiopulmonary rowing test; PL = placebo; RPE = ratio of perceived exertion; OxS = oxygen saturation

Table 1. Descriptive characteristics of international and national rowers.

Variables	International (Mean ± SD)	National (Mean ± SD)
Participants	N = 3	N = 7
Age (years)	37.33 ± 9.45	36.29 ± 2.63
Height (m)	1.82 ± 0.03	1.79 ± 0.05
Weight (kg)	84.85 ± 1.35	79.60 ± 12.70
BMI (kg·m^−2)	25.58 ± 0.69	24.72 ± 2.90
$\dot{V}{\mathrm{O}}_{2max}$ (mL·kg^−1·min^−1)	51.70 ± 1.99	45.16 ± 5.44

Data are presented as means and their standard deviation (Mean ± SD). Abbreviations used: BMI = body mass index, $\dot{V}{\mathrm{O}}_{2max}$ = maximal oxygen uptake.

Figure 3. Differences between the experimental conditions and individual response of each participant: (a) time trial. (b) Relative maximal oxygen uptake ($\dot{V}{\mathrm{O}}_{2max}$).

Abbreviations: BRJ = beetroot juice; PL = placebo. Significant improvements after BRJ intake compared to PL (p ≤ 0.05)

Table 2. Effects of beetroot juice intake on the variables assessed.

Variables	BRJ (Mean ± SD)	PL (Mean ± SD)	MD; ±90%CL	Qualitative Inference
Performance
Time trial (mm:ss)	07:30 ± 40	07:35 ± 44	4.00; ±3.10	Possibly beneficial^a*
Mean Power output (W)	269.99 ± 83.56	269.06 ± 89.35	0.93; ±4.70	Unclear
Mean strokes per minute	29.78 ± 2.99	30.07 ± 2.73	0.29; ±0.45	Most likely trivial^b
Meters per stroke	9.07 ± 0.40	8.94 ± 0.40	0.13; ±0.20	Most likely trivial^b
Cardiorespiratory
$\dot{V}{\mathrm{O}}_{2max}$ (L·min^−1)	3.80 ± 0.60	3.64 ± 0.74	0.16; ±0.11	Possibly +ive^e*
$\dot{V}{\mathrm{O}}_{2max}$ (mL·kg^−1·min^−1)	47.12 ± 5.53	45.03 ± 6.66	2.10; ±1.80	Possibly +ive^e*
$\dot{V}{\mathrm{O}}_{2\mathit{mean}}$(L·min^−1)	3.58 ± 0.60	3.41 ± 0.81	0.17; ±0.16	Possibly +ive^e*
$\dot{V}{\mathrm{O}}_{2\mathit{mean}}$ (mL·kg^−1·min^−1)	43.93 ± 4.67	41.58 ± 7.05	2.35; ±2.35	Possibly +ive^e*
$\dot{V}{\mathrm{O}}_{2max}$ (%)	93.14 ± 3.87	91.70 ± 5.48	1.44; ±2.80	Likely trivial^d
HRmax (beats·min^−1)	186.10 ± 5.36	185.08 ± 5.30	1.02; ±0.98	Possibly +ive^e
HRmean (beats·min^−1)	181.83 ± 5.83	180.66 ± 6.62	1.17; ±1.10	Possibly +ive^e
VE·VCO2^−1 slope	32.33 ± 6.69	31.09 ± 3.79	1.24; ±2.30	Very likely trivial^c
VEmax (L·min^−1)	152.40 ± 18.05	144.90 ± 25.35	7.50; ±6.60	Likely +ive^f
VEmean (L·min^−1)	133.47 ± 14.14	127.66 ± 22.36	5.81; ±6.20	Possibly +ive^e
Others
Lactate (mmol·L^−1)	19.70 ± 2.97	18.73 ± 3.94	0.97; ±2.20	Very likely trivial^c
Saturation (%)	94.20 ± 1.32	94.10 ± 0.88	0.10; ±0.51	Most likely trivial^b
RPE	9.50 ± 0.47	9.45 ± 0.69	0.05; ±0.52	Most likely trivial^b

Data are presented as means and their standard deviation (mean ± SD). +ive o −ive substantial positive or negative changes in the experimental condition with beetroot juice compared to placebo. Abbreviations: BRJ = beetroot juice; CL = confidence limits; HR_max = maximum heart rate; HR_mean = mean heart rate; MD = mean difference; PL = placebo; RPE = rating of perceived exertion; VE_max = maximum ventilation; VE_mean = mean ventilation; $\dot{V}{\mathrm{O}}_{2max}$ = maximal oxygen uptake; $\dot{V}{\mathrm{O}}_{2\mathit{mean}}$ = mean oxygen uptake. *Significant improvements after BRJ intake compared to PL (p ≤ 0.05). a The inference about the magnitude of the effect on trial time was tested using the smallest significant change in trial performance over competitive distance. Effects on other variables were evaluated by standardization; b 0.5%, most unlikely; c 0.5% to 5%, very unlikely; d 5% to 25%, unlikely; e 25% to 75%, possibly; f 75% to 95%, likely; g 95% to 99.5%, very likely; h > 99.5%, most likely or almost certain.

Data availability statement

All data of this study will be available upon reasonable request. Requests should be sent to the corresponding author.