Influence of muscle oxygenation and nitrate-rich beetroot juice supplementation on O2 uptake kinetics and exercise tolerance

Abstract

We tested the hypothesis that acute supplementation with nitrate (NO3 -)-rich beetroot juice (BR) would improve quadriceps muscle oxygenation, pulmonary oxygen uptake ( O2) kinetics and exercise tolerance (Tlim) in normoxia and that these improvements would be augmented in hypoxia and attenuated in hyperoxia. In a randomized, double-blind, cross-over study, ten healthy males completed two-step cycle tests to Tlim following acute consumption of 210 mL BR (18.6 mmol NO3 -) and NO3 --depleted beetroot juice placebo (PL; 0.12 mmol NO3 -). These tests were completed in normobaric normoxia [fraction of inspired oxygen content (FIO2): 21%], hypoxia (FIO2: 15%) and hyperoxia (FIO2: 40%). Pulmonary O2 and quadriceps tissue oxygenation index (TOI), derived from multi-channel near-infrared spectroscopy, were measured during all trials. Plasma [nitrite] was higher in all BR compared to all PL trials (P<0.05). Quadriceps TOI was higher in normoxia compared to hypoxia (P<0.05) and higher in hyperoxia compared to hypoxia and normoxia (P<0.05). Tlim was improved after BR compared to PL ingestion in the hypoxic trials (250 ± 44 vs. 231 ± 41 s; P=0.006; d=1.13), with the magnitude of improvement being negatively correlated with quadriceps TOI at Tlim (r

Influence of Dietary Nitrate Supplementation on High-Intensity Intermittent Running Performance at Different Doses of Normobaric Hypoxia in Endurance-Trained Males

“…Plasma [NO 2 − ] was lowered by a similar magnitude postexercise compared with preexercise across the BR trials in normoxia and both hypoxic doses, with postexercise plasma [NO 2 − ] higher in the BR compared with the PLA trials. These observations are consistent with previous reports of a similar decline in plasma [NO 2 − ] during exhaustive exercise in normoxia and hypoxia (Cocksedge et al, 2020;Kelly et al, 2014) and suggest that circulating NO 2 − is used as a substrate and reduced to bioactive NO. Interestingly, the rate of decline in plasma [NO 2 − ] during the exhaustive high-intensity intermittent running protocol was similar after BR supplementation in the 0 and 1,200-m conditions but was greater than both these conditions in 2,400 m. This novel observation suggests that the greater plasma NO 2 − pool after BR supplementation is only used more rapidly during exhaustive intermittent exercise after moderate, but not low, hypoxic conditions compared with normoxia.…”

“…Since the reduction of NO 2 − to NO is enhanced as PO 2 declines (Jones et al, 2016), there has been great interest in the ergogenic potential of NO 3 − supplementation in hypoxia. In recreationally active or moderately trained individuals, NO 3 − supplementation has been reported to improve continuous endurance performance in normobaric hypoxia (Cocksedge et al, 2020;Kelly et al, 2014;Masschelein et al, 2012;Muggeridge et al, 2014), with greater improvements in hypoxia compared with normoxia (Cocksedge et al, 2020;Kelly et al, 2014). Although the effects of NO 3 − supplementation on continuous endurance performance in normobaric hypoxia in trained individuals are less clear (Arnold et al, 2015;Bourdillon et al, 2015;MacLeod et al, 2015;Nybäck et al, 2017;Rokkedal-Lausch et al, 2019), there is evidence to suggest that, in contrast to normoxia (Porcelli et al, 2015), improved performance with NO 3 − supplementation in hypoxia is not linked to aerobic fitness (Shannon et al, 2016).…”

“…It is well documented that arterial and muscle oxygen saturation decline dose dependently as the hypoxic dose is increased (Goodall et al, 2010). Since the improvements in performance following BR supplementation in hypoxia are greatest in those presenting with lower muscle oxygenation (Cocksedge et al, 2020), it was hypothesized that BR supplementation would progressively enhance high-intensity intermittent running performance as the hypoxic dose was increased.…”

Effects of Dietary Nitrate Supplementation on Performance and Muscle Oxygenation during Resistance Exercise in Men

“…In contrast, NO 3 − has also been shown to be ineffective at influencing muscle oxygenation [66,[77][78][79]. In hypoxic states, NO 3 − supplementation has been shown to preserve muscle oxygenation [80,81] but also shown to have no effect [82]. Therefore, our data suggest that improved bench press RTF after acute NO 3 − supplementation is not linked to altered pectoralis major tissue oxygenation.…”

Effect of PEMF on Muscle Oxygenation during Cycling: A Single-Blind Controlled Pilot Study

“…Previous reports show that changes in NO levels influence muscle PO 2 mv during transitions of metabolic demand, suggesting that augmented NO-mediated function could, at least in part, enhance muscle microvascular oxygenation in trainers [35]. More recently, Cocksedge et al [36] found that beetroot juice (supplements rich of NO 3 − ) has no effect on TOI, VO 2 kinetics, and exercise tolerance when severe intensity exercise (similar to our results; 3.49 vs. 3.46 L/min) occurred in normoxia with respect to hypoxia. The authors concluded that NO supplementation during severe exercise is related to the level of muscle deoxygenation sustained during such exercise intensity.…”