The Relationship between Resistance Exercise Performance and Ventilatory Efficiency after Beetroot Juice Intake in Well-Trained Athletes

Abstract

The assessment of ventilatory efficiency is critical to understanding the matching of ventilation (VE) and perfusion in the lungs during exercise. This study aimed to establish a causal physiological relationship between ventilatory efficiency and resistance exercise performance after beetroot juice (BJ) intake. Eleven well-trained males performed a resistance exercise test after drinking 140 mL of BJ (~12.8 mmol NO₃^-) or a placebo (PL). Ventilatory efficiency was assessed by the VE•VCO₂^-1 slope, the oxygen uptake efficiency slope and the partial pressure of end-tidal carbon dioxide (PetCO₂). The two experimental conditions were controlled using a randomized, double-blind crossover design. The resistance exercise test involved repeating the same routine twice, which consisted of wall ball shots plus a full squat (FS) with a 3 min rest or without a rest between the two exercises. A higher weight lifted was detected in the FS exercise after BJ intake compared with the PL during the first routine (p = 0.004). BJ improved the VE•VCO₂^-1 slope and the PetCO₂ during the FS exercise in the first routine and at rest (p < 0.05). BJ intake improved the VE•VCO₂^-1 slope and the PetCO₂ coinciding with the resistance exercise performance. The ergogenic effect of BJ could be induced under aerobic conditions at rest.

Keywords: VE•VCO2−1 slope; nitrate; nitric oxide; nitrite; oxygen uptake efficiency slope; partial pressure of end-tidal carbon dioxide.

Figure 1

Procedures during the resistance exercise test after beetroot juice (BJ) intake and the placebo (PL) condition of the third and fourth session/BJ or PL randomized, double-blind, crossover design. Abbreviations used: BJ: beetroot juice; CPET: cardiopulmonary exercise test; FS: full squat; NOx: nitrate plus nitrite; PL: placebo; WBS: wall ball shots.

Figure 2

Total weight lifted (n = 11). Abbreviations used: BJ: beetroot juice; FS-R1: full squat during the first routine; FS-R2: full squat during the second routine; PL: placebo; WBS-R1: wall ball shots during the first routine; WBS-R2: wall ball shots during the second routine. Data are provided as mean and error bars as 95% confidence intervals. * Significant increase in the total weight lifted after BJ intake compared with the PL condition in the first routine (with a 3 min rest) (p = 0.004).

Figure 3

Differences between beetroot juice intake and the placebo (n = 11). (a) VE•VCO₂⁻¹ slope (b) OUES. Abbreviations used: BJ: beetroot juice; FS-R1: full squat during the first routine; OUES: oxygen uptake efficiency slope; PL: placebo; WBS-R1: wall ball shots during the first routine; WBS+FS-R2: wall ball shots plus full squat during the second routine (without a rest). Data are provided as mean and error bars as 95% confidence intervals. * Significant increase in the VE•VCO₂⁻¹ slope after the PL intake compared with BJ (p < 0.05).

Figure 4

Relationship between ventilation (VE) and carbon dioxide (VE•VCO₂⁻¹ slope) after beetroot juice (a) and a placebo (b) (n = 11).

Figure 5

Relationship between oxygen uptake (VO₂) log₁₀ ventilation (VE) (OUES) after beetroot juice (a) and a placebo (b) (n = 11).

Figure 6

Differences between beetroot juice intake and the placebo in the partial pressure of end-tidal carbon dioxide (PetCO₂) (n = 11). Abbreviations used: BJ: beetroot juice; FS-R1: full squat during the first routine; PL: placebo; WBS-R1: wall ball shots during the first routine; WBS+FS-R2: wall ball shots plus full squat during the second routine (without a rest). Data are provided as mean and error bars as 95% confidence intervals. * Significant increase in the PetCO₂ after BJ intake compared with PL (p < 0.001).