Mmol NO3 Research Articles

Muddy (silty-sand) beaches in semi-arid regions attenuate the contaminants flowing into the sea as a submarine groundwater discharge

Urbanized coastal areas are well-recognized hotspots for the contaminant-enriched groundwater discharge, influencing sensitive coastal ecosystems. The present study investigates how muddy beaches in the semi-arid region alter the contaminant flux flowing into the sea using submarine groundwater discharge (SGD) estimation and hydrogeochemical analysis of coastal waters (groundwater, porewater, and seawater). Fresh SGD carries contaminants such as nutrients and trace metals in the coastal ecosystem, causing increased vulnerability towards eutrophication, harmful algal blooms, and human health. We found that SGD reaching the coast carries immense nutrient flux (155.6 mmol NO3− · day−1; 35 mmol P · day−1 and 12.4 mmol DSi · day−1) and trace metal load ranging from 0.1 to 14.9 mmol · day−1. The nutrient fluxes were higher in the upper saline plume compared to the lower plume. The muddy beach attenuates the nutrients in varying percentages of 9.7 to 22% of NO3−, 1.9 to 25.5% of P due to denitrification and phosphorus absorption, and also caused 19.6% reduction of SO42−. The reduction in SO42− leads to the formation of sulfide (HS−) that promotes the metal precipitation, resulting in the removal of Pb and Cu. This attenuation of nutrients leads to a change in the nutrient ratio (N/P = 7–11) approaching the Redfield ratio, implying the vulnerability of algal bloom at the Dehri beach. Overall, the muddy beach can serve as a natural biogeochemical reactor as it attenuates the nutrient and serves as a source for certain trace metals (Fe, Mn, Zn, and Ni), altering the composition of SGD. Probably this is the first study that emphasizes the attenuation of trace metals in the muddy beaches of a semi-arid region.

No effect of nitrate-rich beetroot juice on microvascular function and blood pressure in younger and older individuals: a randomised, placebo-controlled double-blind pilot study

Background/ObjectivesTo compare the effects of supplemental inorganic nitrate (NO3) on microvascular endothelial function and blood pressure in younger vs. older participants.Subjects/Methods25 individuals participated in a double-blind, randomised, placebo-controlled crossover pilot study. Participants were stratified by age (18–35 and ≥55 years) and consumed a single dose beetroot juice (providing 6.4 mmol NO3) or NO3-depleted beetroot juice. Blood pressure, microvascular function (via Laser Doppler Flowmetry; LDF) and urinary NO3 were assessed, and the effects of NO3 supplementation on cardiovascular parameters were compared between participants and conditions using mixed-design ANOVA.ResultsTreatments and methods were well tolerated, and no adverse events were reported. Urinary NO3 increased 3 h following ingestion in both groups, (P = 0.02). Levels remained elevated at 24 h post consumption in younger participants only (P = 0.02). Beetroot juice had no effect on blood pressure in either group nor on microcirculatory endothelial function.ConclusionsBeetroot juice had no effect on blood pressure or microvascular endothelial function in young and older individuals. Dosage and timing regimens for supplemental beetroot juice should be avenues for further inquiry.

Influence of Chronic Nitrate-Rich Beetroot Juice Supplementation on the Endurance Performance of Active Winter Triathletes: A Randomized Controlled Trial

Objective: The impact of high-nitrate beetroot juice (BRJ) supplementation has seen a recent explosion of interest in sports science. This study examined the potential influence of 7-day BRJ supplementation on the endurance performance of winter triathletes. Methods: Eighty young active winter triathletes (44 males, age = 21.50 ± 1.15 yrs; 36 females, age = 20.66 ± 1.45 yrs) participated in this study and were provided with either BRJ (6.5 mmol NO3 −/70 mL) or a placebo (PL, 0.065 mmol NO3 −/70 mL) for 7 days (a dose of ×3 per day) in a randomized, double-blind design. The athletes then completed a submaximal treadmill run, intraday cycling exhaustion testing, and a 10-km cross country (XC) skiing competition on the second day. Results: There was a significant decrease in the oxygen uptake, respiratory exchange ratio, and blood lactic acid level (p < 0.05) between the BRJ and PL treatment groups during V 3 speed running (males: 13.3 km·h−1, females: 11.6 km·h−1). BRJ treatment also remarkably increased the time to exhaustion (TTE) during cycling exhaustion testing (males: p = 0.02, females: p = 0.04). No significant differences were observed in medium- or low-speed submaximal treadmill runs and 10-km XC skiing performance. Conclusions: One week of daily nitrate-rich BRJ supplementation improved running economy at high speed during the submaximal treadmill running test and extended the TTE of athletes during cycling exhaustion testing. However, BRJ supplementation did not improve the performance in 10-km on-snow time trials in XC skiing. Regarding nutritional strategies to improve endurance performance in exercise training and competition, these results should be carefully considered owing to the different motor skill levels and competitive abilities of participants.

On the implication of dietary nitrate supplementation for the hemodynamic and fatigue response to cycling exercise.

This study investigated the impact of dietary nitrate supplementation on peripheral hemodynamics, the development of neuromuscular fatigue, and time to task failure during cycling exercise. Eleven recreationally active male participants (27 ± 5 yr, V̇o2max: 42 ± 2 mL/kg/min) performed two experimental trials following 3 days of either dietary nitrate-rich beetroot juice (4.1 mmol NO3-/day; DNS) or placebo (PLA) supplementation in a blinded, counterbalanced order. Exercise consisted of constant-load cycling at 50, 75, and 100 W (4 min each) and, at ∼80% of peak power output (218 ± 12 W), to task-failure. All participants returned to repeat the shorter of the two trials performed to task failure, but with the opposite supplementation regime (iso-time comparison; ISO). Mean arterial pressure (MAP), leg blood flow (QL; Doppler ultrasound), leg vascular conductance (LVC), and pulmonary gas exchange were continuously assessed during exercise. Locomotor muscle fatigue was determined by the change in pre to postexercise quadriceps twitch-torque (ΔQtw) and voluntary activation (ΔVA; electrical femoral nerve stimulation). Following DNS, plasma [nitrite] (∼670 vs. ∼180 nmol) and [nitrate] (∼775 vs. ∼11 μmol) were significantly elevated compared with PLA. Unlike PLA, DNS lowered both QL and MAP by ∼8% (P < 0.05), but did not alter LVC (P = 0.31). V̇O2 across work rates, as well as cycling time to task-failure (∼7 min) and locomotor muscle fatigue following the ISO-time comparison were not different between the two conditions (ΔQtw ∼42%, ΔVA ∼4%). Thus, despite significant hemodynamic changes, DNS did not alter the development of locomotor muscle fatigue and, ultimately, cycling time to task failure.NEW & NOTEWORTHY This study sought to characterize the impact of dietary nitrate supplementation on the hemodynamic response, locomotor muscle fatigue, and time to task failure during cycling exercise. Although nitrate supplementation lowered mean arterial pressure and exercising leg blood flow, leg vascular conductance and oxygen utilization were unaffected. Despite significant hemodynamic changes, there was no effect of dietary nitrate on neuromuscular fatigue development and, ultimately, cycling time to task failure.

Nitrate alleviate dissimilatory iron reduction and arsenic mobilization by driving microbial community structure change

Anaerobic situation induced by long-term flooding of paddy soils makes dissimilatory iron (Fe) reduction and Arsenic (As) reduction in pore water. In our research, different dosage of nitrate (1 and 20 mmol NO3− kg−1 soil, LN and HN, respectively) were used as amendments for As immobilization. The effect on soil properties such as pH, Eh, sulfate, and nitrate; the effect on As(III) and dissimilatory iron reduction and the effect on microbial community structure were investigated. Our results showed that With the addition of nitrate, the reduction of Eh was accelerated. Especially for HN, the Eh decreased from 139 to 40 mV in 30 days, is higher than Eh in original soil (CK). The dissimilatory iron reduction was significantly depressed by the addition of nitrate, Fe2+ in nitrate amendments are much less than control, especially for HN, Fe2+ concentration was 62.58% lower than control. While Final As(III) concentrations were 284.67, 223.87, and 190.70mg Kg−1 for CK, LN, and HN treatments, respectively. In both LN and HN, the concentration of NO3− faded with incubation time, which means that NO3− could act as an electron acceptor instead of Fe3+ and As(V). Moreover, nitrate has selectivity for microbes, while the abundance of Clostridia and Geobacteraceae, which play a major role in the reduction of dissimilatory iron, is strongly inhibited, thereby inhibiting the process of dissimilatory iron reduction. Our results showed that by promotion of decreasing Eh, inhibition dissimilatory iron reduction, and Arsenic speciation transformation, nitrate could act as an effective amendment for As immobilization in paddy soils.

The effect of beetroot juice supplementation on muscle performance during isokinetic knee extensions in male Taekwondo athletes

Summary Objectives Little information is available regarding the effects of beetroot juice (BRJ) on muscle performance and contractions during resistance exercise. The muscle strength and power of the lower extremity is an important attribute in Taekwondo, therefore, present study examines the effects of 6 days of BRJ supplementations on muscle performance during isokinetic contractions of knee muscle in male Taekwondo athletes. Equipments and methods Twelve male Taekwondo athletes (age, 19.2 ± 1.6 yrs) were volunteered to take part in this double-blind, placebo-controlled, randomized crossover design. Participants consumed either 140 mL nitrate-rich concentrated BRJ (∼12.8 mmol NO3−) or placebo (blackcurrant juice) for six consecutive days. On the last day of supplementation, the knee extensions were performed on a Biodex isokinetic dynamometer. Treatment periods were separated by a 10-day washout periods. Results Knee extensor peak torque increased significantly (P

Tropical Beaches Attenuate Groundwater Nitrogen Pollution Flowing to the Ocean.

Tropical urbanized coastal regions are hotspots for the discharge of nutrient-enriched groundwater, which can affect sensitive coastal ecosystems. Here, we investigated how a beach modifies groundwater nutrient loads in southern India (Varkala Beach), using flux measurements and stable isotopes. Fresh groundwater was highly enriched in NO3 from sewage or manure. Submarine groundwater discharge and nearshore groundwater discharge were equally important contributors to coastal NO3 fluxes with 303 mmol NO3 m-1 day-1 in submarine and 334 mmol NO3 m-1 day-1 in nearshore groundwater discharge. However, N/P ratios in nearshore groundwater discharge were up to 3 orders of magnitude greater than that in submarine groundwater, which can promote harmful algae blooms. As groundwater flowed through the beach, N/P ratios decreased toward Redfield ratios due to the removal of 30-50% of NO3 due to denitrification and production of PO4 due to mineralization of organic matter. Overall, tropical beaches can be important natural biogeochemical reactors that attenuate nitrogen pollution and modify N/P ratios in submarine groundwater discharge.

Nitrogen‐Loads to Streams: Importance of Bypass Flow and Nitrate Removal Processes

AbstractN‐loads from subsurface, drains, and groundwater‐fed surface (bypass) flows via two riparian zones (crop field and wetland) to a second order stream were investigated by sampling of shallow and deep groundwater on both sides and monthly measurements of bypass flows from springs, drains, and stream including water quality (nitrate). A push‐pull test in the crop field gave a first‐order denitrification rate (0.23 day–1). Reactive transport modeling evaluated observations of water chemistry and denitrification processes in the groundwater below the crop field showing that nitrate was completely removed by denitrification with pyrite in the aquifer (model rates of 0.6–2.5 mmol NO3 L−1 yr−1). A drain in the crop field routed ∼10% (bypass) of the regional groundwater inflow to the stream. Buffer efficiency was high at 90%. The wetland on the other side of the stream hosts several locations of nitrate‐rich bypass flow from springs, predominantly through a non‐maintained drainage system of drainpipes and ditches with bypass flow accounting for 59% of the regional flow input. Nitrate was completely removed in groundwater by denitrification with dissolved organic matter in shallow groundwater. The regional inflow and N load to the wetland is amongst the highest recorded and data shows that the N load to the stream is very high. The buffer efficiency ranged from 45% to 83% depending on if all bypass flows contributed to the stream or only the two with visible outflow. A conceptual model for nitrate removal efficiency as a function of Damköhler number and percent bypass flow is proposed.

S-nitrosothiols, and other products of nitrate metabolism, are increased in multiple human blood compartments following ingestion of beetroot juice

Ingested inorganic nitrate (NO3⁻) has multiple effects in the human body including vasodilation, inhibition of platelet aggregation, and improved skeletal muscle function. The functional effects of oral NO3⁻ involve the in vivo reduction of NO3⁻ to nitrite (NO2⁻) and thence to nitric oxide (NO). However, the potential involvement of S-nitrosothiol (RSNO) formation is unclear. We hypothesised that the RSNO concentration ([RSNO]) in red blood cells (RBCs) and plasma is increased by NO3⁻-rich beetroot juice ingestion. In healthy human volunteers, we tested the effect of dietary supplementation with NO3⁻-rich beetroot juice (BR) or NO3⁻-depleted beetroot juice (placebo; PL) on [RSNO], [NO3⁻] and [NO2⁻] in RBCs, whole blood and plasma, as measured by ozone-based chemiluminescence. The median basal [RSNO] in plasma samples (n = 22) was 10 (5–13) nM (interquartile range in brackets). In comparison, the median values for basal [RSNO] in the corresponding RBC preparations (n = 19) and whole blood samples (n = 19) were higher (p < 0.001) than in plasma, being 40 (30–60) nM and 35 (25–80) nM, respectively. The median RBC [RSNO] in a separate cohort of healthy subjects (n = 5) was increased to 110 (93–125) nM after ingesting BR (12.8 mmol NO3⁻) compared to a corresponding baseline value of 25 (21–31) nM (Mann-Whitney test, p < 0.01). The median plasma [RSNO] in another cohort of healthy subjects (n = 14) was increased almost ten-fold to 104 (58–151) nM after BR supplementation (7 × 6.4 mmol of NO3⁻ over two days, p < 0.01) compared to PL. In conclusion, RBC and plasma [RSNO] are increased by BR ingestion. In addition to NO2⁻, RSNO may be involved in dietary NO3⁻ metabolism/actions.

Multiple-day high-dose beetroot juice supplementation does not improve pulmonary or muscle deoxygenation kinetics of well-trained cyclists in normoxia and hypoxia

Dietary nitrate (NO3−) supplementation via beetroot juice (BR) has been reported to lower oxygen cost (i.e., increased exercise efficiency) and speed up oxygen uptake (VO2) kinetics in untrained and moderately trained individuals, particularly during conditions of low oxygen availability (i.e., hypoxia). However, the effects of multiple-day, high dose (12.4 mmol NO3− per day) BR supplementation on exercise efficiency and VO2 kinetics during normoxia and hypoxia in well-trained individuals are not resolved. In a double-blinded, randomized crossover study, 12 well-trained cyclists (66.4 ± 5.3 ml min−1∙kg−1) completed three transitions from rest to moderate-intensity (~70% of gas exchange threshold) cycling in hypoxia and normoxia with supplementation of BR or nitrate-depleted BR as placebo. Continuous measures of VO2 and muscle (vastus lateralis) deoxygenation (ΔHHb, using near-infrared spectroscopy) were acquired during all transitions. Kinetics of VO2 and deoxygenation (ΔHHb) were modeled using mono-exponential functions. Our results showed that BR supplementation did not alter the primary time constant for VO2 or ΔHHb during the transition from rest to moderate-intensity cycling. While BR supplementation lowered the amplitude of the VO2 response (2.1%, p = 0.038), BR did not alter steady state VO2 derived from the fit (p = 0.258), raw VO2 data (p = 0.231), moderate intensity exercise efficiency (p = 0.333) nor steady state ΔHHb (p = 0.224). Altogether, these results demonstrate that multiple-day, high-dose BR supplementation does not alter exercise efficiency or oxygen uptake kinetics during normoxia and hypoxia in well-trained athletes.

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

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.

Effect of Dietary Nitrate Supplementation on Sleep in Chronic Obstructive Pulmonary Disease Patients.

PurposePoor sleep quality in chronic obstructive pulmonary disease (COPD) is a result of oxygen desaturation secondary to compromised lung function. Nitrate supplementation with dietary beetroot juice is known to elevate plasma nitrate and to increase the efficiency of oxygen utilization in non-COPD individuals; whether it is of therapeutic benefit for sleep quality in COPD has not been reported.Patients and MethodsIn a counterbalanced within-subjects design involving 15 COPD patients as subjects, the subjects consumed either beetroot juice containing nitrate (BJ; ∼6.2 mmol NO3–) or placebo (NO3– -depleted juice) immediately before a night of polysomnographic monitoring. Nitrate was measured in plasma collected immediately after waking.ResultsWhile BJ consumption had no effect on the amount of time spent in any sleep stages, wake-to-N2 transitions and direct wake-to-rapid eye movement sleep (REMS) transitions, hallmarks of disordered sleep, were less frequent on the BJ night than on the placebo night. In the last two hours of the BJ night, percent time in REMS increased and delta power during deep (N3) non-REMS decreased, relative to the placebo night. Collectively, the reduced frequency of atypical transitions and the normalization of non-REMS/REMS dynamics after BJ are indicative of an improvement of sleep quality. BJ also resulted in sustained elevation of peripheral oxygen saturation (SpO2), during episodes of wake after sleep onset. Plasma nitrate was elevated nearly tenfold on the morning after BJ relative to placebo.ConclusionBJ has a normalizing effect on disordered sleep in COPD, which may be related to improved oxygen delivery.Clinical Trial RegistrationThe activities of the Regional Committees for Medical and Health Research Ethics (REC) are founded on the Norwegian law on research ethics and medical research. This study was approved by NTNU/REK midt, Det medisinske fakultet, Postboks 8905, 7491 Trondheim (REK midt 2016/1360).

Influence of Sex and Acute Beetroot Juice Supplementation on 2 KM Running Performance

Purpose: To assess the effect of acute nitrate-rich (BJ) and nitrate-depleted (PL) beetroot juice ingestion on 2 km running performance in amateur runners, and to what extent the ergogenic effect of BJ supplementation would be influenced by the sex of the participants; Methods: Twenty-four amateur long-distance runners (14 males and 10 females) performed a 2 km time trial (TT) on an outdoor athletics track 2.5 h after ingesting either 140 mL of BJ (~12.8 mmol NO3−) or PL. After the tests, blood [lactate] and ratings of perceived exertion (RPE) related to the leg muscles (RPEmuscular), cardiovascular system (RPEcardio) and general overall RPE (RPEgeneral) were assessed; Results: Compared to PL, BJ supplementation improved 2 km TT performance in both males (p &lt; 0.05) with no supplement × sex interaction effect (p &gt; 0.05). This improvement in 2 km running performance was a function of improved performance in the second 1 km split time in both males and females (p &lt; 0.05). Supplementation with BJ did not alter post-exercise blood [lactate] (p &gt; 0.05) but lowered RPEgeneral (p &lt; 0.05); Conclusions: acute BJ supplementation improves 2 km running performance in amateur runners by enhancing performance over the second half of the TT and lowering RPEgeneral by a comparable magnitude in males and females.

Nitrate-rich beetroot juice offsets salivary acidity following carbohydrate ingestion before and after endurance exercise in healthy male runners.

There have been recent calls for strategies to improve oral health in athletes. High carbohydrate diets, exercise induced dehydration and transient perturbations to immune function combine to increase oral disease risk in this group. We tested whether a single dose of nitrate (NO3-) would offset the reduction in salivary pH following carbohydrate ingestion before and after an exercise bout designed to cause mild dehydration. Eleven trained male runners ( 53 ± 9 ml∙kg-1∙min-1, age 30 ± 7 years) completed a randomised placebo-controlled study comprising four experimental trials. Participants ingested the following fluids one hour before each trial: (a) 140 ml of water (negative-control), (b) 140 ml of water (positive-control), (c) 140 ml of NO3- rich beetroot juice (~12.4 mmol NO3-) (NO3- trial) or (d) 140 ml NO3- depleted beetroot juice (placebo-trial). During the negative-control trial, participants ingested 795 ml of water in three equal aliquots: before, during, and after 90 min of submaximal running. In the other trials they received 795 ml of carbohydrate supplements in the same fashion. Venous blood was collected before and after the exercise bout and saliva was sampled before and repeatedly over the 20 min following carbohydrate or water ingestion. As expected, nitrite (NO2-) and NO3- were higher in plasma and saliva during the NO3- trial than all other trials (all P<0.001). Compared to the negative-control, salivary-pH was significantly reduced following the ingestion of carbohydrate in the positive-control and placebo trials (both P <0.05). Salivary-pH was similar between the negative-control and NO3- trials before and after exercise despite ingestion of carbohydrate in the NO3- trial (both P≥0.221). Ingesting NO3- attenuates the expected reduction in salivary-pH following carbohydrate supplements and exercise-induced dehydration. NO3- should be considered by athletes as a novel nutritional strategy to reduce the risk of developing acidity related oral health conditions.

Acute Beetroot Juice Supplementation Does Not Improve Match-Play Activity in Professional Tennis Players

Objective Beetroot juice is a source of dietary nitrate (NO3-) recognized as a potential ergogenic aid to enhance tolerance during endurance exercise of submaximal-to-maximal intensity. However, little is known about the effects of beetroot juice on exercise performance in intermittent sports such as tennis. The present study aimed to determine the effect of acute beetroot juice supplementation on movement patterns during a competitive tennis match in professional players. Methods In a double-blind and randomized experiment, nine professional tennis players performed two experimental trials 3 h after ingesting either 70 mL of a commercially-available concentrated beetroot juice (6.4 mmol NO3-) or placebo (0.005 mmol NO3-). In each experimental trial, players completed a 3-set tennis match and two performance tests (i.e., serve speed and isometric handgrip strength) before and after the match. Match-play running performance was recorded using wearable GPS and accelerometer units. Results In comparison to the placebo trial, the acute beetroot juice supplementation did not modify any match-play running performance (p = 0.178 to 0.997, d = 0.01 to 0.42). Furthermore, beetroot juice supplementation did not alter the pre-to-post match change in serve speed (p = 0.663, ηp 2 = 0.03) or isometric handgrip strength (p = 0.219, ηp 2 = 0.18). Conclusions: The current results indicated that acute ingestion of a commercialized shot of nitrate-rich beetroot juice (70 mL containing 6.4 mmol of NO3-) did not produce any performance benefit on tennis matchplay. Thus, acute beetroot juice supplementation seems an ergogenic aid with little value to enhance physical performance in professional tennis players.

1021 Effect of Dietary Nitrate Supplementation on Sleep in Chronic Obstructive Pulmonary Disease Patients

Abstract Introduction Chronic obstructive pulmonary disease (COPD) requires the use of accessory muscles to overcome inadequate ventilation. The activity of these voluntary muscles is compromised during sleep, resulting in insufficient ventilation, oxygen desaturation and disruption of sleep. Nitrate supplementation with dietary beetroot juice (DBJ) is known to increase the efficiency of oxygen utilization in non-COPD individuals; its therapeutic effect in COPD is uncertain. Methods In a repeated measured experiment involving 15 COPD patients, subjects consumed either 70 mL of beetroot juice containing nitrate (~6.2 mmol NO3-) or placebo (NO3--depleted juice) immediately before bedtime. Sleep states were defined based on F4-O2 electroencephalogram and masseter electromyogram. All subjects spent at least 6.2 hrs in bed; the data analysis was therefore restricted to the first 6 hrs in bed. Results Standard polysomnography indicated no changes in the amount of time spent in any sleep stages. Wake-to-N2 transitions were greater than two-fold more frequent after placebo (a total of 21 observed) than DBJ (9 observed), resulting in a significant main effect of treatment (F1,14=7.3, P=0.017). N2-to-wake transitions were nearly 3-fold more frequent after placebo (a total of 35 observed) than DBJ (12 observed), resulting in a significant main effect of treatment (F1,14=2.52, P=0.024). Direct wake-to-REMS transitions were observed four times after placebo and never after DBJ (F1,14=2.26, P=0.041). DBJ also resulted in sustained elevation of peripheral oxygen saturation (SpO2), measured by pulse oximetry, during episodes of wake after sleep onset (WASO). Two minutes into WASO after DBJ SpO2 was elevated by 1.09 + 0.31% relative to pre-WASO; two minutes into WASO after placebo SpO2 was elevated by 0.08 + 0.54% relative to pre-WASO (P=0.012). Conclusion Collectively, the reduced frequency of atypical transitions after DBJ are indicative of an improvement of sleep quality. DBJ is thus a potential adjunct therapy for disordered sleep in COPD. Support N/A

Dietary nitrate does not acutely enhance skeletal muscle blood flow and vasodilation in the lower limbs of older adults during single-limb exercise.

Blood flow (BF) and vasodilator responses to knee-extension exercise are attenuated in older adults across an exercise transient (onset, kinetics, and steady-state), and reduced nitric oxide bioavailability (NO) has been hypothesized to be a primary mechanism contributing to this attenuation. We tested the hypothesis acute dietary nitrate (NO3-) supplementation (~ 4.03mmol NO3- and 0.29mmol NO2-) would improve leg vasodilator responses across an exercise transient during lower limb exercise in older adults. Older (n = 10) untrained adults performed single and rhythmic knee-extension contractions at 20% and 40% work-rate maximum (WRmax) prior to and 2-h after consuming a NO3- or placebo beverage in a double-blind, randomized fashion. Femoral artery BF was measured by Doppler ultrasound. Vascular conductance was calculated using BF and mean arterial pressure. Acute ingestion of dietary NO3- enhanced plasma [NO3-] and [NO2-] (P < 0.05). Neither dietary NO3- or placebo enhanced vasodilator responses at the onset of exercise or during steady state at 20% and 40% WRmax (P > 0.05). Leg vasodilator kinetics during rhythmic exercise remained unchanged following NO3- and placebo ingestion (P > 0.05). The key findings of this study are that despite increasing plasma [NO3-] and [NO2-], acute dietary NO3- intake had no effect on (1) rapid hyperaemic or vasodilator responses at the onset of exercise; (2) hyperaemic and vasodilator responses during steady-state submaximal exercise; or (3) kinetics of vasodilation preceding steady-state responses. Collectively, these findings suggest that low dose dietary NO3- supplementation does not improve hyperaemic and vasodilator responses across an exercise transient in older adults.

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

We tested the hypothesis that acute supplementation with nitrate (NO3−)-rich beetroot juice (BR) would improve quadriceps muscle oxygenation, pulmonary oxygen uptake (V˙O2) kinetics and exercise tolerance (Tlim) in normoxia and that these improvements would be augmented in hypoxia and attenuated in hyperoxia. In a randomised, 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−) or NO3−-depleted beetroot juice placebo (PL; 0.12 mmol NO3−). These tests were completed in normobaric normoxia [fraction of inspired oxygen (FIO2): 21%], hypoxia (FIO2: 15%) and hyperoxia (FIO2: 40%). Pulmonary V˙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 = −0.78; P < 0.05). Tlim was not improved following BR ingestion in normoxia (BR: 364 ± 98 vs. PL: 344 ± 78 s; P = 0.087, d = 0.61) or hyperoxia (BR: 492 ± 212 vs. PL: 472 ± 196 s; P = 0.273, d = 0.37). BR ingestion increased peak V˙O2 in hypoxia (P < 0.05), but not normoxia or hyperoxia (P > 0.05). These findings indicate that BR supplementation is more likely to improve Tlim and peak V˙O2 in situations when skeletal muscle is more hypoxic.

Dietary nitrate supplementation does not alter V̇O2p gain during ramp incremental cycling exercise

In a previous study 15 days of dietary nitrate/nitrite (NO3−/NO2−) supplementation was associated with a lower V̇O2p gain (ΔV̇O2p/ΔPower Output; PO) in the moderate (MOD) intensity exercise domain and a higher V̇O2p gain for exercise above lactate threshold (θL) 1. It remains unclear how V̇O2p gain is affected within the heavy‐ (HVY; supra‐θL, infra‐respiratory compensation point [RCP]) and very heavy‐intensity (VH; supra‐RCP) exercise domains during ramp incremental (RI) exercise to the limit of tolerance (LoT).PURPOSETo investigate the role of 20 days of dietary NO3−/NO2− supplementation on V̇O2p gain during a ramp incremental‐sprint (RISP) exercise protocol.METHODSUsing a double‐blind, block randomised, repeated measures design, 8 healthy, active males (age 24 ± 2 yr [mean ± SD]; V̇O2p‐max 44 ± 6 mL O2·kg−1·min−1) consumed NO3−‐rich (N+; 12.8 mmol NO3−) or ‐depleted (PL; 0.08 mmol NO3−) beetroot juice per day for 20 days. Prior to supplementation participants completed a RISP test consisting of 6 min baseline leg cycling at 25 W, RI exercise (25 W·min−1) to the LoT, and, after 3 min resting recovery, a 3 min variable PO sprint protocol. V̇O2p was measured breath‐by‐breath. No exercise was conducted on days 1–5 of supplementation. Constant‐load VH (6 bouts with each bout lasting 3–18 min) or MOD (1 bout lasting 18 min) were performed on alternate days during days 6–18. On day 20, participants completed a final RISP test. After a 14‐day washout period the protocol was repeated with participants consuming the other supplement condition.RESULTSPre‐supplement baseline plasma [NO3−] and [NO2−] were not different (P &gt; 0.05) between N+ and PL, but were elevated (P &lt; 0.05) on days 6, 14, and 20 of N+ supplementation (NO3−: 32 ± 14 μM at BSL to 325 ± 143 μM; NO2−: 119 ± 130 nM at BSL to 245 ± 155 nM). There were no differences (P &gt; 0.05) between NO3−‐rich and ‐depleted conditions in V̇O2p gain within the MOD (N+, 9.3 ± 1.2 vs PL, 9.4 ± 1.2 mL O2·min−1·W−1), HVY (N+, 9.3 ± 0.9 vs PL, 9.1 ± 1.2 mL O2·min−1·W−1), VH (N+, 9.7 ± 2.2 vs PL, 9.1 ± 1.9 mL O2·min−1·W−1; P = 0.173) domains or whole ramp (N+, 9.6 ± 0.7 vs PL, 9.2 ± 1.0 mL O2·min−1·W−1; P = 0.119). No differences were found in V̇O2p at θL (N+, 2.10 ± 0.50 vs PL, 2.04 ± 0.52 L·min−1) or RCP (N+, 3.06 ± 0.63 vs PL, 3.00 ± 0.67 L·min−1), or between V̇O2p‐peak measured at end‐ramp or the final 20s of the sprint between N+ and PL and within N+ and PL (End‐ramp: N+, 3.67 ± 0.69 vs PL, 3.51 ± 0.73 mL·min−1 [P = 0.101]; Sprint: N+, 3.70 ± 0.66 vs PL, 3.57 ± 0.67 mL·min−1 [P = 0.08]).CONCLUSIONDespite elevated plasma [NO3−] and [NO2−], V̇O2p gains were unaffected in the MOD, HVY, or VH intensity domains assessed throughout RI exercise. These data suggest O2 utilization efficiency in contracting quadriceps muscle is not impacted by elevated plasma [NO3−] and [NO2−], at least within the conditions of the current study.Support or Funding InformationFunded by NSERC and James White Drinks

No thermoregulatory or ergogenic effect of dietary nitrate among physically inactive males, exercising above gas exchange threshold in hot and dry conditions

The aim of this study was to determine the effect of five days dietary nitrate (NO3 −) consumption on exercise tolerance and thermoregulation during cycling in hot, dry conditions. In a double-blind, randomised crossover design, 11 healthy males participated in an exercise tolerance test (Tlim) in the heat (35°C, 28% relative humidity), cycling above the thermoneutral gas exchange threshold, after five days of dietary supplementation, with either NO3 –rich beetroot juice (BR; ∼ 9.2 mmol NO3 −) or placebo (PLA). Changes in plasma [NO3 −] and nitrite [NO2 −], core and mean skin temperatures, mean local and whole-body sweat rates, heart rate, perceptual ratings and pulmonary gas exchange were measured during exercise, alongside calorimetric estimations of thermal balance. Mean arterial pressures (MAP) were recorded pre-Tlim. There were no differences in Tlim between conditions (BR = 22.8 ± 8.1 min; Placebo = 20.7 ± 7.9 min) (P = 0.184), despite increases in plasma [NO3 −] and [NO2 −] (P < 0.001) and a 3.8% reduction in resting MAP (P = 0.004) in the BR condition. There were no other differences in thermoregulatory, cardio-metabolic, perceptual or calorimetric responses to the Tlim between conditions (P > 0.05). Dietary NO3 − supplementation had no effect on exercise tolerance or thermoregulation in hot, dry conditions, despite reductions in resting MAP and increases in plasma [NO3 −] and [NO2 −]. Healthy, yet physically inactive individuals with no known impairments in vasodilatory and sudomotor function do not appear to require BR for ergogenic or thermolytic effects during exercise in the heat.