Understanding the effects of beetroot juice intake on CrossFit performance by assessing hormonal, metabolic and mechanical response: a randomized, double-blind, crossover design

Abstract

Background Acute beetroot juice (BJ) intake has shown to enhance aerobic and anaerobic performance. However, no studies have evaluated the effects of BJ intake on CrossFit (CF) performance by linking hormonal, metabolic, and mechanical responses. The purpose of this study was to determine the causal physiological association between hormonal, metabolic and mechanical responses, and CF workouts performance after acute BJ intake. Methods Twelve well-trained male practitioners undertook a CF workout after drinking 140 mL of BJ (~ 12.8 mmol NO3−) or placebo. The two experimental conditions (BJ or placebo) were administered using a randomized, double-blind, crossover design. The CF workout consisted of repeating the same exercise routine twice: Wall ball (WB) shots plus full back squat (FBS) with 3-min rest (1st routine) or without rest (2nd routine) between the two exercises. A 3-min rest was established between the two exercise routines. Results An interaction effect was observed in the number of repetitions performed (p = 0.04). The Bonferroni test determined a higher number of repetitions after BJ than placebo intake when a 3-min rest between WB and FBS (1st routine) was established (p = 0.007). An interaction effect was detected in cortisol response (p = 0.04). Cortisol showed a higher increase after BJ compared to placebo intake (76% vs. 36%, respectively). No interaction effect was observed in the testosterone and testosterone/cortisol ratio (p > 0.05). A significant interaction effect was found in oxygen saturation (p = 0.01). A greater oxygen saturation drop was observed in BJ compared to placebo (p < 0.05). An interaction effect was verified in muscular fatigue (p = 0.03) with a higher muscular fatigue being observed with BJ than placebo (p = 0.02). Conclusions BJ intake improved anaerobic performance only after the recovery time between exercises. This increase in performance in the first routine probably generated greater hypoxia in the muscle mass involved, possibly conditioning post-exercise performance. This was observed with a fall in oxygen saturation and in muscle fatigue measured at the end of the CF workout. The greatest perceived changes in cortisol levels after BJ intake could be attributed to the nitrate-nitrite-nitric oxide pathway.

Cardiorespiratory, Metabolic and Muscular Responses during a Video-Recorded Aerobic Dance Session on an Air Dissipation Platform

“…Muscular fatigue has been assessed by CMJ test in several studies that analyzed cardiorespiratory and metabolic responses [ 12 , 13 , 18 ]. Despite finding a greater cardiometabolic and ventilatory stress on an ADP than on a hard surface, mechanical fatigue on an ADP was not augmented compared to a hard surface.…”

“…It is tempting to speculate that the different mechanical work and energy costs induced by different surfaces on the musculoskeletal system could lead to variations in muscular fatigue. Several studies have used vertical jump height (i.e., counter movement jump) before and after exercise to assess the extent of muscular fatigue [ 12 , 13 ]. However, muscular fatigue assessed by a countermovement jump test before and after an AD session has not been explored by comparing an ADP and a hard surface.…”

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

“…A nutrition professional controlled the BJ and PL intake and the diet according to the guidelines established in previous studies [ 34 , 35 ]. The diet control was established in a food diary 48 h before sessions 3 and 4.…”

“…As in a previous study [ 34 ], BJ or the PL was ingested 3 h before the start of sessions 3 and 4. The participants were provided with a randomly assigned garnet red plastic bottle containing 140 mL of BJ Beet-It-Pro Elite Shot concentrate (~12.8 mmol, ~808 mg NO 3 − ) (Beet IT; James White Drinks Ltd., Ipswich, UK) or the PL.…”

“…Recently, we demonstrated that BJ increased anaerobic performance only after the recovery time between exercises during a high intensity resistance exercise test in well-trained athletes. We also observed that BJ did not improve performance compared with the placebo group when anaerobic conditions were increased with no rest between resistance exercises [ 34 ]. The effects of BJ on the performance of well-trained athletes led to discrepancies among researchers.…”