Circulating nitrate-nitrite reduces oxygen uptake for improving resistance exercise performance after rest time in well-trained CrossFit athletes

Figure 1. CONSORT flowchart.

Figure 2. Procedures. 1RM, one-repetition maximum; BC, blood collection; BJ, beetroot juice; CK, creatin kinase; CPRET, cardiopulmonary resistance exercise test; FBS, full back squat; LDH, Lactate dehydrogenase; NOx, nitrate plus nitrite; PL, placebo; WBS, wall ball shots.

Figure 3. Circulating NOx concentrations in plasma. BJ, beetroot juice; NOx, nitrate plus nitrite; PL, placebo. ★A significant raise in plasma NOx concentrations after BJ intake compared to PL in pretest and posttest (p < 0.001). ☨Significantly higher increase in post-test than in pretest in PL condition (p < 0.05).

Figure 4. Repetitions completed after beetroot juice and placebo intake. Data are provided as mean and error bars as 95% confidence intervals. 1stR, first routine; 2ndR, second routine; BJ, beetroot juice; FBS, full back squat; PL, placebo; WBS, wall ball shots. ★A significant increase in the FBS repetitions performed after BJ intake compared to PL condition in the first routine (with 3-min rest) (p = 0.004). ☨Repetitions were significantly increased in the WBS and FBS exercises in the first routine compared the second routine (without rest) in the two experimental conditions (p ≤ 0.012).

Figure 5. Oxygen uptake (A) and ventilation (B) after beetroot juice and placebo intake. Data are provided as mean and error bars as 95% confidence intervals. BJ, beetroot juice; FBS, full back squat; PL, placebo; RTbE, rest time between exercises; RTbR, rest time between routines; VE, minute ventilation; VO2, oxygen uptake; WBS, wall ball shots. ★A significant increase in the VO2 and VE after PL compared to BJ intake (p < 0.05).

Figure 6. Plasma concentrations of myoglobin (A), creatin kinase (B) and lactate dehydrogenase (C). BJ, beetroot juice; CK, creatin kinase; LDH, lactate dehydrogenase; PL, placebo. ★A significant increase in post-test compared to pretest in the two experimental conditions (p < 0.05). ☨Significantly higher increase after BJ intake (101.2%) than in PL condition 36.9% (p < 0.05).