Relationships between nitric oxide biomarkers and physiological outcomes following dietary nitrate supplementation.

Dietary nitrate (NO3-) supplementation can increase nitric oxide (NO) bioavailability, reduce blood pressure (BP) and improve muscle contractile function in humans. Plasma nitrite concentration (plasma [NO2-]) is the most oft-used biomarker of NO bioavailability. However, it is unclear which of several NO biomarkers (NO3-, NO2-, S-nitrosothiols (RSNOs)) in plasma, whole blood (WB), red blood cells (RBC) and skeletal muscle correlate with the physiological effects of acute and chronic dietary NO3- supplementation. Using a randomized, double-blind, crossover design, 12 participants (9 males) consumed NO3--rich beetroot juice (BR) (∼12.8 mmol NO3-) and NO3--depleted placebo beetroot juice (PL) acutely and then chronically (for two weeks). Biological samples were collected, resting BP was assessed, and 10 maximal voluntary isometric contractions of the knee extensors were performed at 2.5-3.5 h following supplement ingestion on day 1 and day 14. Diastolic BP was significantly lower in BR (-2 ± 3 mmHg, P = 0.03) compared to PL following acute supplementation, while the absolute rate of torque development (RTD) was significantly greater in BR at 0-30 ms (39 ± 57 N m s-1, P = 0.03) and 0-50 ms (79 ± 99 N m s-1, P = 0.02) compared to PL following two weeks supplementation. Greater WB [RSNOs] rather than plasma [NO2-] was correlated with lower diastolic BP (r = -0.68, P = 0.02) in BR compared to PL following acute supplementation, while greater skeletal muscle [NO3-] was correlated with greater RTD at 0-30 ms (r = 0.64, P=0.03) in BR compared to PL following chronic supplementation. We conclude that [RSNOs] in blood, and [NO3-] in skeletal muscle, are relevant biomarkers of NO bioavailability which are related to the reduction of BP and the enhanced muscle contractile function following dietary NO3- ingestion in humans.

Vegan and Omnivorous High Protein Diets Support Comparable Daily Myofibrillar Protein Synthesis Rates and Skeletal Muscle Hypertrophy in Young Adults.

BACKGROUND: It remains unclear whether non-animal-derived dietary protein sources (and therefore vegan diets) can support resistance training-induced skeletal muscle remodeling to the same extent as animal-derived protein sources. METHODS: In Phase 1, 16 healthy young adults (m = 8, f = 8; age: 23 ± 1 y; BMI: 23 ± 1 kg/m2) completed a 3-d dietary intervention (high protein, 1.8 g·kg bm-1·d-1) where protein was derived from omnivorous (OMNI1; n = 8) or exclusively non-animal (VEG1; n = 8) sources, alongside daily unilateral leg resistance exercise. Resting and exercised daily myofibrillar protein synthesis (MyoPS) rates were assessed using deuterium oxide. In Phase 2, 22 healthy young adults (m = 11, f = 11; age: 24 ± 1 y; BMI: 23 ± 0 kg/m2) completed a 10 wk, high-volume (5 d/wk), progressive resistance exercise program while consuming an omnivorous (OMNI2; n = 12) or non-animal-derived (VEG2; n = 10) high-protein diet (∼2 g·kg bm-1·d-1). Muscle fiber cross-sectional area (CSA), whole-body lean mass (via DXA), thigh muscle volume (via MRI), muscle strength, and muscle function were determined pre, after 2 and 5 wk, and postintervention. OBJECTIVES: To investigate whether a high-protein, mycoprotein-rich, non-animal-derived diet can support resistance training-induced skeletal muscle remodeling to the same extent as an isonitrogenous omnivorous diet. RESULTS: Daily MyoPS rates were ∼12% higher in the exercised than in the rested leg (2.46 ± 0.27%·d-1 compared with 2.20 ± 0.33%·d-1 and 2.62 ± 0.56%·d-1 compared with 2.36 ± 0.53%·d-1 in OMNI1 and VEG1, respectively; P < 0.001) and not different between groups (P > 0.05). Resistance training increased lean mass in both groups by a similar magnitude (OMNI2 2.6 ± 1.1 kg, VEG2 3.1 ± 2.5 kg; P > 0.05). Likewise, training comparably increased thigh muscle volume (OMNI2 8.3 ± 3.6%, VEG2 8.3 ± 4.1%; P > 0.05), and muscle fiber CSA (OMNI2 33 ± 24%, VEG2 32 ± 48%; P > 0.05). Both groups increased strength (1 repetition maximum) of multiple muscle groups, to comparable degrees. CONCLUSIONS: Omnivorous and vegan diets can support comparable rested and exercised daily MyoPS rates in healthy young adults consuming a high-protein diet. This translates to similar skeletal muscle adaptive responses during prolonged high-volume resistance training, irrespective of dietary protein provenance. This trial was registered at clinicaltrials.gov as NCT03572127.

The effect of various breath-hold techniques on the cardiorespiratory response to facial immersion in humans.

NEW FINDINGS: What is the central question of this study? What is the effect of three repeated breath-hold techniques routinely used by freedivers, thought to manipulate arterial partial pressures of O2 and CO2 , on the cardiorespiratory and haematological response to breath-holding during facial immersion? What is the main finding and its importance? All three techniques increased breath-hold by a similar duration, probably owing to the similar marked increase in end-tidal O2 and decrease in end-tidal CO2 observed in all three trials before facial immersion. These were the only cardiorespiratory changes that were consistently manipulated before the maximal breath-hold. This would suggest that pronounced bradycardia and vasoconstriction of selective vascular beds are probably not obligatory for prolonging breath-hold duration. ABSTRACT: Repeated maximal breath-holds have been demonstrated to induce bradycardia, increase haematocrit and haemoglobin and prolong subsequent breath-hold duration by 20%. Freedivers use non-maximal breath-hold techniques (BHTs) to improve breath-hold duration. The aim of this study was to investigate the cardiorespiratory and haematological responses to various BHTs. Ten healthy men (34.5 ± 1.9 years) attended five randomized experimental trials and performed a 40 min period of quiet rest or one of three BHTs followed by a maximal breath-hold challenge during facial immersion in water at 30 or 10°C. Cardiovascular and respiratory parameters were measured continuously using finger plethysmography and breath-by-breath gas analysis, respectively, and venous blood samples were collected throughout. Facial immersion in cold water caused marked bradycardia (74.1 vs. 50.2 beats/min after 40 s) but did not increase breath-hold duration compared with warm water control conditions. Facial immersion breath-hold duration was 30.8-43.3% greater than the control duration when preceded by BHTs that involved repeated breath-holds of constant duration (P = 0.021), increasing duration (P < 0.001) or increasing frequency (P < 0.001), with no difference observed between BHTs. The increased duration of apnoea across all three BHT protocols was associated with a 6.8% increase in end-tidal O2 and a 13.1% decrease in end-tidal CO2 immediately before facial immersion. There were no differences in blood pressure, cardiac output, heart rate, haematocrit or haemoglobin between each BHT and control conditions (P > 0.05). In conclusion, the duration of apnoea can be extended by manipulating blood gases through repeated prior breath-holds, but changes in cardiac output and red blood cell mass do not appear essential.

Mycoprotein ingestion within or without its wholefood matrix results in equivalent stimulation of myofibrillar protein synthesis rates in resting and exercised muscle of young men.

Ingestion of mycoprotein stimulates skeletal muscle protein synthesis (MPS) rates to a greater extent than concentrated milk protein when matched for leucine content, potentially attributable to the wholefood nature of mycoprotein. We hypothesised that bolus ingestion of mycoprotein as part of its wholefood matrix would stimulate MPS rates to a greater extent compared with a leucine-matched bolus of protein concentrated from mycoprotein. Twenty-four healthy young (age, 21 ± 2 years; BMI, 24 ± 3 kg.m2) males received primed, continuous infusions of L-[ring-2H5]phenylalanine and completed a bout of unilateral resistance leg exercise before ingesting either 70 g mycoprotein (MYC; 31·4 g protein, 2·5 g leucine; n 12) or 38·2 g of a protein concentrate obtained from mycoprotein (PCM; 28·0 g protein, 2·5 g leucine; n 12). Blood and muscle samples (vastus lateralis) were taken pre- and (4 h) post-exercise/protein ingestion to assess postabsorptive and postprandial myofibrillar protein fractional synthetic rates (FSR) in resting and exercised muscle. Protein ingestion increased plasma essential amino acid and leucine concentrations (P < 0·0001), but more rapidly (both 60 v. 90 min; P < 0·0001) and to greater magnitudes (1367 v. 1346 µmol·l-1 and 298 v. 283 µmol·l-1, respectively; P < 0·0001) in PCM compared with MYC. Protein ingestion increased myofibrillar FSR (P < 0·0001) in both rested (MYC, Δ0·031 ± 0·007 %·h-1 and PCM, Δ0·020 ± 0·008 %·h-1) and exercised (MYC, Δ0·057 ± 0·011 %·h-1 and PCM, Δ0·058 ± 0·012 %·h-1) muscle, with no differences between conditions (P > 0·05). Mycoprotein ingestion results in equivalent postprandial stimulation of resting and post-exercise myofibrillar protein synthesis rates irrespective of whether it is consumed within or without its wholefood matrix.

Daily protein-polyphenol ingestion increases daily myofibrillar protein synthesis rates and promotes early muscle functional gains during resistance training.

Factors underpinning the time-course of resistance-type exercise training (RET) adaptations are not fully understood. This study hypothesized that consuming a twice-daily protein-polyphenol beverage (PPB; n = 15; age, 24 ± 1 yr; BMI, 22.3 ± 0.7 kg·m-2) previously shown to accelerate recovery from muscle damage and increase daily myofibrillar protein synthesis (MyoPS) rates would accelerate early (10 sessions) improvements in muscle function and potentiate quadriceps volume and muscle fiber cross-sectional area (fCSA) following 30 unilateral RET sessions in healthy, recreationally active, adults. Versus isocaloric placebo (PLA; n = 14; age, 25 ± 2 yr; BMI, 23.9 ± 1.0 kg·m-2), PPB increased 48 h MyoPS rates after the first RET session measured using deuterated water (2.01 ± 0.15 vs. 1.51 ± 0.16%·day-1, respectively; P < 0.05). In addition, PPB increased isokinetic muscle function over 10 sessions of training relative to the untrained control leg (%U) from 99.9 ± 1.8 pretraining to 107.2 ± 2.4%U at session 10 (vs. 102.6 ± 3.9 to 100.8 ± 2.4%U at session 10 in PLA; interaction P < 0.05). Pre to posttraining, PPB increased type II fCSA (PLA: 120.8 ± 8.2 to 109.5 ± 8.6%U; PPB: 92.8 ± 6.2 to 108.4 ± 9.7%U; interaction P < 0.05), but the gain in quadriceps muscle volume was similar between groups. Similarly, PPB did not further increase peak isometric torque, muscle function, or MyoPS measured posttraining. This suggests that although PPB increases MyoPS and early adaptation, it may not influence longer term adaptations to unilateral RET.NEW & NOTEWORTHY Using a unilateral model of resistance training, we show for the first time that a protein-polyphenol beverage increases initial rates of myofibrillar protein synthesis and promotes early functional improvements. Following a prolonged period of training, this strategy also increases type II fiber hypertrophy and causes large individual variation in gains in quadricep muscle cross-sectional area.

Physiological and performance effects of dietary nitrate and N-acetylcysteine supplementation during prolonged heavy-intensity cycling.

The purpose of this study was to investigate effects of concurrent and independent administration of dietary nitrate (NO3-), administered as NO3--rich beetroot juice (BR; ~12.4 mmol of NO3-), and N-acetylcysteine (NAC; 70 mg·kg-1) on physiological responses during prolonged exercise and subsequent high-intensity exercise tolerance. Sixteen recreationally active males supplemented with NO3--depleted beetroot juice (PL) or BR for 6 days and ingested an acute dose of NAC or maltodextrin (MAL) 1 h prior to performing 1 h of heavy-intensity cycling exercise immediately followed by a severe-intensity time-to-exhaustion (TTE) test in four conditions: 1) PL+MAL, 2) PL+NAC, 3) BR+MAL and 4) BR+NAC. Pre-exercise plasma [NO3-] and nitrite ([NO2-]) were elevated following BR+NAC  and BR+MAL (both P < 0.01) compared with PL+NAC and PL+MAL; plasma [cysteine] was increased in PL+NAC  and BR+NAC (both P < 0.01) compared to PL+MAL. Muscle excitability declined over time during the prolonged cycling bout in all conditions  but was better preserved in PL+NAC  compared to BR+NAC (P < 0.01) and PL+MAL (P < 0.05). There was no effect of supplementation on subsequent TTE . These findings indicate that co-ingestion of BR and NAC does not appreciably alter physiological responses during prolonged heavy-intensity cycling or enhance subsequent exercise tolerance.

Nitrate-rich beetroot juice ingestion reduces skeletal muscle O2 uptake and blood flow during exercise in sedentary men.

Dietary nitrate supplementation has been shown to reduce pulmonary O2 uptake during submaximal exercise and enhance exercise performance. However, the effects of nitrate supplementation on local metabolic and haemodynamic regulation in contracting human skeletal muscle remain unclear. To address this, eight healthy young male sedentary subjects were assigned in a randomized, double-blind, crossover design to receive nitrate-rich beetroot juice (NO3, 9 mmol) and placebo (PLA) 2.5 h prior to the completion of a double-step knee-extensor exercise protocol that included a transition from unloaded to moderate-intensity exercise (MOD) followed immediately by a transition to intense exercise (HIGH). Compared with PLA, NO3 increased plasma levels of nitrate and nitrite. During MOD, leg V̇O2 and leg blood flow (LBF) were reduced to a similar extent (∼9%-15%) in NO3. During HIGH, leg V̇O2 was reduced by ∼6%-10% and LBF by ∼5%-9% (did not reach significance) in NO3. Leg V̇O2 kinetics was markedly faster in the transition from passive to MOD compared with the transition from MOD to HIGH both in NO3 and PLA with no difference between PLA and NO3. In NO3, a reduction in nitrate and nitrite concentration was detected between arterial and venous samples. No difference in the time to exhaustion was observed between conditions. In conclusion, elevation of plasma nitrate and nitrate reduces leg skeletal muscle V̇O2 and blood flow during exercise. However, nitrate supplementation does not enhance muscle V̇O2 kinetics during exercise, nor does it improve time to exhaustion when exercising with a small muscle mass. KEY POINTS: Dietary nitrate supplementation has been shown to reduce systemic O2 uptake during exercise and improve exercise performance. The effects of nitrate supplementation on local metabolism and blood flow regulation in contracting human skeletal muscle remain unclear. By using leg exercise engaging a small muscle mass, we show that O2 uptake and blood flow are similarly reduced in contracting skeletal muscle of humans during exercise. Despite slower V̇O2 kinetics in the transition from moderate to intense exercise, no effects of nitrate supplementation were observed for V̇O2 kinetics and time to exhaustion. Nitrate and nitrite concentrations are reduced across the exercising leg, suggesting that these ions are extracted from the arterial blood by contracting skeletal muscle.

Lowering of blood pressure after nitrate-rich vegetable consumption is abolished with the co-ingestion of thiocyanate-rich vegetables in healthy normotensive males.

A diet rich in vegetables is known to provide cardioprotection. However, it is unclear how the consumption of different vegetables might interact to influence vascular health. This study tested the hypothesis that nitrate-rich vegetable consumption would lower systolic blood pressure but that this effect would be abolished when nitrate-rich and thiocyanate-rich vegetables are co-ingested. On four separate occasions, and in a randomized cross-over design, eleven healthy males reported to the laboratory and consumed a 750 mL vegetable smoothie that was either: low in nitrate (∼0.3 mmol) and thiocyanate (∼5 µmol), low in nitrate and high in thiocyanate (∼72 µmol), high in nitrate (∼4 mmol) and low in thiocyanate and high in nitrate and thiocyanate. Blood pressure as well as plasma and salivary [thiocyanate], [nitrate] and [nitrite] were assessed before and 3 h after smoothie consumption. Plasma [nitrate] and [nitrite] and salivary [nitrate] were not different after consuming the two high-nitrate smoothies, but salivary [nitrite] was higher after consuming the high-nitrate low-thiocyanate smoothie (1183 ±â€¯625 µM) compared to the high-nitrate high-thiocyanate smoothie (941 ±â€¯532 µM; P < .001). Systolic blood pressure was only lowered after consuming the high-nitrate low-thiocyanate smoothie (-3 ±â€¯5 mmHg; P < .05). The acute consumption of vegetables high in nitrate and low in thiocyanate lowered systolic blood pressure. However, when the same dose of nitrate-rich vegetables was co-ingested with thiocyanate-rich vegetables the increase in salivary [nitrite] was smaller and systolic blood pressure was not lowered. These findings might have implications for optimising dietary guidelines aimed at improving cardiovascular health.

Leveraging Big Data Towards Functionally-Based, Catchment Scale Restoration Prioritization.

The persistence of freshwater degradation has necessitated the growth of an expansive stream and wetland restoration industry, yet restoration prioritization at broad spatial extents is still limited and ad-hoc restoration prevails. The River Basin Restoration Prioritization tool has been developed to incorporate vetted, distributed data models into a catchment scale restoration prioritization framework. Catchment baseline condition and potential improvement with restoration activity is calculated for all National Hydrography Dataset stream reaches and catchments in North Carolina and compared to other catchments within the river subbasin to assess where restoration efforts may best be focused. Hydrologic, water quality, and aquatic habitat quality conditions are assessed with peak flood flow, nitrogen and phosphorus loading, and aquatic species distribution models. The modular nature of the tool leaves ample opportunity for future incorporation of novel and improved datasets to better represent the holistic health of a watershed, and the nature of the datasets used herein allow this framework to be applied at much broader scales than North Carolina.

Influence of iodide ingestion on nitrate metabolism and blood pressure following short-term dietary nitrate supplementation in healthy normotensive adults.

Uptake of inorganic nitrate (NO3-) into the salivary circulation is a rate-limiting step for dietary NO3- metabolism in mammals. It has been suggested that salivary NO3- uptake occurs in competition with inorganic iodide (I-). Therefore, this study tested the hypothesis that I- supplementation would interfere with NO3- metabolism and blunt blood pressure reductions after dietary NO3- supplementation. Nine healthy adults (4 male, mean ± SD, age 20 ± 1 yr) reported to the laboratory for initial baseline assessment (control) and following six day supplementation periods with 140 mL·day-1 NO3--rich beetroot juice (8.4 mmol NO3-·day-1) and 198 mg potassium gluconate·day-1 (nitrate), and 140 mL·day-1 NO3--rich beetroot juice and 450 µg potassium iodide·day-1 (nitrate + iodide) in a randomized, cross-over experiment. Salivary [I-] was higher in the nitrate + iodide compared to the control and NIT trials (P < 0.05). Salivary and plasma [NO3-] and [NO2-] were higher in the nitrate and nitrate + iodide trials compared to the control trial (P < 0.05). Plasma [NO3-] was higher (474 ± 127 vs. 438 ± 117 µM) and the salivary-plasma [NO3-] ratio was lower (14 ± 6 vs. 20 ± 6 µM), indicative of a lower salivary NO3- uptake, in the nitrate + iodide trial compared to the nitrate trial (P < 0.05). Plasma and salivary [NO2-] were not different between the nitrate and nitrate + iodide trials (P > 0.05). Systolic blood pressure was lower than control (112 ± 13 mmHg) in the nitrate (106 ± 13 mmHg) and nitrate + iodide (106 ± 11 mmHg) trials (P < 0.05), with no differences between the nitrate and nitrate + iodide trials (P > 0.05). In conclusion, co-ingesting NO3- and I- perturbed salivary NO3- uptake, but the increase in salivary and plasma [NO2-] and the lowering of blood pressure were similar compared to NO3- ingestion alone. Therefore, increased dietary I- intake, which is recommended in several countries worldwide as an initiative to offset hypothyroidism, does not appear to compromise the blood pressure reduction afforded by increased dietary NO3- intake.

The mechanistic bases of the power-time relationship: muscle metabolic responses and relationships to muscle fibre type.

KEY POINTS: The power-asymptote (critical power; CP) of the hyperbolic power-time relationship for high-intensity exercise defines a threshold between steady-state and non-steady-state exercise intensities and the curvature constant (W') indicates a fixed capacity for work >CP that is related to a loss of muscular efficiency. The present study reports novel evidence on the muscle metabolic underpinnings of CP and W' during whole-body exercise and their relationships to muscle fibre type. We show that the W' is not correlated with muscle fibre type distribution and that it represents an elevated energy contribution from both oxidative and glycolytic/glycogenolytic metabolism. We show that there is a positive correlation between CP and highly oxidative type I muscle fibres and that muscle metabolic steady-state is attainable CP. Our findings indicate a mechanistic link between the bioenergetic characteristics of muscle fibre types and the power-time relationship for high-intensity exercise. ABSTRACT: We hypothesized that: (1) the critical power (CP) will represent a boundary separating steady-state from non-steady-state muscle metabolic responses during whole-body exercise and (2) that the CP and the curvature constant (W') of the power-time relationship for high-intensity exercise will be correlated with type I and type IIx muscle fibre distributions, respectively. Four men and four women performed a 3 min all-out cycling test for the estimation of CP and constant work rate (CWR) tests slightly >CP until exhaustion (Tlim ), slightly CP Tlim isotime to test the first hypothesis. Eleven men performed 3 min all-out tests and donated muscle biopsies to test the second hypothesis. Below CP, muscle [PCr] [42.6 ± 7.1 vs. 49.4 ± 6.9 mmol (kg d.w.)(-1) ], [La(-) ] [34.8 ± 12.6 vs. 35.5 ± 13.2 mmol (kg d.w.)(-1) ] and pH (7.11 ± 0.08 vs. 7.10 ± 0.11) remained stable between ∼12 and 24 min (P > 0.05 for all), whereas these variables changed with time >CP such that they were greater [[La(-) ] 95.6 ± 14.1 mmol (kg d.w.)(-1) ] and lower [[PCr] 24.2 ± 3.9 mmol (kg d.w.)(-1) ; pH 6.84 ± 0.06] (P < 0.05) at Tlim (740 ± 186 s) than during the

Two weeks of watermelon juice supplementation improves nitric oxide bioavailability but not endurance exercise performance in humans.

This study tested the hypothesis that watermelon juice supplementation would improve nitric oxide bioavailability and exercise performance. Eight healthy recreationally-active adult males reported to the laboratory on two occasions for initial testing without dietary supplementation (control condition). Thereafter, participants were randomly assigned, in a cross-over experimental design, to receive 16 days of supplementation with 300 mL·day(-1) of a watermelon juice concentrate, which provided ∼3.4 g l-citrulline·day(-1) and an apple juice concentrate as a placebo. Participants reported to the laboratory on days 14 and 16 of supplementation to assess the effects of the interventions on blood pressure, plasma [l-citrulline], plasma [l-arginine], plasma [nitrite], muscle oxygenation and time-to-exhaustion during severe-intensity exercise. Compared to control and placebo, plasma [l-citrulline] (29 ± 4, 22 ± 6 and 101 ± 23 µM), [l-arginine] (74 ± 9, 67 ± 13 and 116 ± 9 µM) and [nitrite] (102 ± 29, 106 ± 21 and 201 ± 106 nM) were higher after watermelon juice supplementation (P < 0.01). However, systolic blood pressure was higher in the watermelon juice (130 ± 11) and placebo (131 ± 9) conditions compared to the control condition (124 ± 8 mmHg; P < 0.05). The skeletal muscle oxygenation index during moderate-intensity exercise was greater in the watermelon juice condition than the placebo and control conditions (P < 0.05), but time-to-exhaustion during the severe-intensity exercise test (control: 478 ± 80, placebo: 539 ± 108, watermelon juice: 550 ± 143 s) was not significantly different between conditions (P < 0.05). In conclusion, while watermelon juice supplementation increased baseline plasma [nitrite] and improved muscle oxygenation during moderate-intensity exercise, it increased resting blood pressure and did not improve time-to-exhaustion during severe-intensity exercise. These findings do not support the use of watermelon juice supplementation as a nutritional intervention to lower blood pressure or improve endurance exercise performance in healthy adults.

Improvement in blood pressure after short-term inorganic nitrate supplementation is attenuated in cigarette smokers compared to non-smoking controls.

Dietary supplementation with inorganic nitrate (NO3-) has been reported to improve cardiovascular health indices in healthy adults. Cigarette smoking increases circulating thiocyanate (SCN-), which has been suggested to competitively inhibit salivary nitrate (NO3-) uptake, a rate-limiting step in dietary NO3- metabolism. Therefore, this study tested the hypothesis that dietary NO3- supplementation would be less effective at increasing the circulating plasma nitrite concentration ([NO2-]) and lowering blood pressure in smokers (S) compared to non-smokers (NS). Nine healthy smokers and eight healthy non-smoking controls reported to the laboratory at baseline (CON) and following six day supplementation periods with 140 mL day-1 NO3--rich (8.4 mmol NO3- day-1; NIT) and NO3--depleted (0.08 mmol NO3- day-1; PLA) beetroot juice in a cross-over experiment. Plasma and salivary [SCN-] were elevated in smokers compared to non-smokers in all experimental conditions (P < 0.05). Plasma and salivary [NO3-] and [NO2-] were elevated in the NIT condition compared to CON and PLA conditions in smokers and non-smokers (P < 0.05). However, the change in salivary [NO3-] (S: 3.5 ± 2.1 vs. NS: 7.5 ± 4.4 mM), plasma [NO3-] (S: 484 ± 198 vs. NS: 802 ± 199 µM) and plasma [NO2-] (S: 218 ± 128 vs. NS: 559 ± 419 nM) between the CON and NIT conditions was lower in the smokers compared to the non-smokers (P < 0.05). Salivary [NO2-] increased above CON to a similar extent with NIT in smokers and non-smokers (P > 0.05). Systolic blood pressure was lowered compared to PLA with NIT in non-smokers (P < 0.05), but not smokers (P > 0.05). These findings suggest that dietary NO3- metabolism is compromised in smokers leading to an attenuated blood pressure reduction compared to non-smokers after NO3- supplementation. These observations may provide novel insights into the cardiovascular risks associated with cigarette smoking and suggest that this population may be less likely to benefit from improved cardiovascular health if they increase dietary NO3- intake.

High-nitrate vegetable diet increases plasma nitrate and nitrite concentrations and reduces blood pressure in healthy women.

OBJECTIVE: Epidemiological studies suggest that green leafy vegetables, which are high in dietary nitrate, are protective against CVD such as stroke. High blood pressure (BP) is a major risk factor for stroke and inorganic nitrate has been shown to reduce BP. The objective of the present study was to test the hypothesis that diets containing high-nitrate (HN) vegetables would increase plasma nitrate and nitrite concentrations and reduce BP in healthy women. DESIGN: A randomized, crossover trial, where participants received HN vegetables (HN diet) or avoided HN vegetables (Control diet) for 1 week. Before and after each intervention, resting BP and plasma nitrate and nitrite concentrations were measured. SETTING: University of Exeter, UK. SUBJECTS: Nineteen healthy women (mean age 20 (sd 2) years; mean BMI 22·5 (sd 3·8) kg/m2). RESULTS: The HN diet significantly increased plasma nitrate concentration (before HN diet: mean 24·4 (sd 5·6) µmol/l; after HN diet: mean 61·0 (sd 44·1) µmol/l, P<0·05) and plasma nitrite concentration (before HN diet: mean 98 (sd 91) nmol/l; after HN diet: mean 185 (sd 34) nmol/l, P<0·05). No significant change in plasma nitrate or nitrite concentration was observed after the Control diet. The HN diet significantly reduced resting systolic BP (before HN diet: mean 107 (sd 9) mmHg; after HN diet: mean 103 (sd 6) mmHg, P<0·05). No significant change in systolic BP was observed after the Control diet (before Control diet: mean 106 (sd 8) mmHg; after Control diet: mean 106 (sd 8) mmHg). CONCLUSIONS: Consumption of HN vegetables significantly increased plasma nitrate and nitrite concentrations and reduced BP in normotensive women.

Influence of dietary nitrate supplementation on human skeletal muscle metabolism and force production during maximum voluntary contractions.

Dietary nitrate supplementation, which enhances nitric oxide (NO) bioavailability, has previously been shown to contribute to improved exercise performance by reducing both oxygen cost and energy expenditure. In contrast, previous studies have indicated that NO can lower force production in vitro. To examine the role of dietary nitrates in regulating force generation under normal physiological conditions, we undertook an extended nitrate supplementation regime and determined force output and energy cost with a repeated isometric maximum voluntary contraction (MVC) protocol. In a double-blind, randomized, crossover design, eight participants received 0.5 l/day of nitrate-rich (BR) or nitrate-depleted (PL) beetroot juice for 15 days and completed an exercise protocol consisting of 50 MVCs at 2.5 h, 5 days and 15 days after the beginning of the supplementation period. No significant reduction in force output was determined for BR relative to PL for the peak contraction, the mean or the end force, and no significant time effect was found over the course of the supplementation period. There was a reduction in the mean PCr cost of exercise averaged over the BR supplementation trials, but this did not reach statistical significance for end exercise (BR 15.10 ± 4.14 mM, PL 17.10 ± 5.34 mM, P = 0.06) or the mean throughout the protocol (BR 15.96 ± 4.14 mM, PL 17.79 ± 4.51 mM, P = 0.06). However, a significant reduction in PCr cost per unit force output was found for BR at end exercise (P = 0.04). These results indicate that, under normal physiological conditions, increased NO bioavailability is not associated with a reduction of force-generating capability in human skeletal muscle and confirm that nitrate supplementation reduces the PCr cost of force production.

Beetroot juice supplementation speeds O2 uptake kinetics and improves exercise tolerance during severe-intensity exercise initiated from an elevated metabolic rate.

Recent research has suggested that dietary nitrate (NO3(-)) supplementation might alter the physiological responses to exercise via specific effects on type II muscle. Severe-intensity exercise initiated from an elevated metabolic rate would be expected to enhance the proportional activation of higher-order (type II) muscle fibers. The purpose of this study was, therefore, to test the hypothesis that, compared with placebo (PL), NO3(-)-rich beetroot juice (BR) supplementation would speed the phase II VO2 kinetics (τ(p)) and enhance exercise tolerance during severe-intensity exercise initiated from a baseline of moderate-intensity exercise. Nine healthy, physically active subjects were assigned in a randomized, double-blind, crossover design to receive BR (140 ml/day, containing ~8 mmol of NO3(-)) and PL (140 ml/day, containing ~0.003 mmol of NO3(-)) for 6 days. On days 4, 5, and 6 of the supplementation periods, subjects completed a double-step exercise protocol that included transitions from unloaded to moderate-intensity exercise (U→M) followed immediately by moderate to severe-intensity exercise (M→S). Compared with PL, BR elevated resting plasma nitrite concentration (PL: 65 ± 32 vs. BR: 348 ± 170 nM, P < 0.01) and reduced the VO2 τ(p) in M→S (PL: 46 ± 13 vs. BR: 36 ± 10 s, P < 0.05) but not U→M (PL: 25 ± 4 vs. BR: 27 ± 6 s, P > 0.05). During M→S exercise, the faster VO2 kinetics coincided with faster near-infrared spectroscopy-derived muscle [deoxyhemoglobin] kinetics (τ; PL: 20 ± 9 vs. BR: 10 ± 3 s, P < 0.05) and a 22% greater time-to-task failure (PL: 521 ± 158 vs. BR: 635 ± 258 s, P < 0.05). Dietary supplementation with NO3(-)-rich BR juice speeds VO2 kinetics and enhances exercise tolerance during severe-intensity exercise when initiated from an elevated metabolic rate.

Effects of short-term dietary nitrate supplementation on blood pressure, O2 uptake kinetics, and muscle and cognitive function in older adults.

Dietary nitrate (NO(3)(-)) supplementation has been shown to reduce resting blood pressure and alter the physiological response to exercise in young adults. We investigated whether these effects might also be evident in older adults. In a double-blind, randomized, crossover study, 12 healthy, older (60-70 yr) adults supplemented their diet for 3 days with either nitrate-rich concentrated beetroot juice (BR; 2 × 70 ml/day, ∼9.6 mmol/day NO(3)(-)) or a nitrate-depleted beetroot juice placebo (PL; 2 × 70 ml/day, ∼0.01 mmol/day NO(3)(-)). Before and after the intervention periods, resting blood pressure and plasma [nitrite] were measured, and subjects completed a battery of physiological and cognitive tests. Nitrate supplementation significantly increased plasma [nitrite] and reduced resting systolic (BR: 115 ± 9 vs. PL: 120 ± 6 mmHg; P < 0.05) and diastolic (BR: 70 ± 5 vs. PL: 73 ± 5 mmHg; P < 0.05) blood pressure. Nitrate supplementation resulted in a speeding of the Vo(2) mean response time (BR: 25 ± 7 vs. PL: 28 ± 7 s; P < 0.05) in the transition from standing rest to treadmill walking, although in contrast to our hypothesis, the O(2) cost of exercise remained unchanged. Functional capacity (6-min walk test), the muscle metabolic response to low-intensity exercise, brain metabolite concentrations, and cognitive function were also not altered. Dietary nitrate supplementation reduced resting blood pressure and improved Vo(2) kinetics during treadmill walking in healthy older adults but did not improve walking or cognitive performance. These results may have implications for the enhancement of cardiovascular health in older age.

No effect of acute L-arginine supplementation on O2 cost or exercise tolerance.

The extent to which dietary supplementation with the nitric oxide synthase (NOS) substrate, L-arginine (ARG), impacts on NO production and NO-mediated physiological responses is controversial. This randomised, double blinded, cross-over study investigated the effects of acute ARG supplementation on NO biomarkers, O2 cost of exercise and exercise tolerance in humans. In one experiment, 15 subjects completed moderate- and severe-intensity running bouts after acute supplementation with 6 g ARG or placebo (PLA). In another experiment, eight subjects completed moderate- and severe-intensity cycling bouts after acute supplementation with 6 g ARG plus 25 g of carbohydrate (ARG + CHO) or an energy-matched dose of carbohydrate alone (CHO). The plasma nitrite concentration was not different after ARG (Pre: 204 ± 79; Post: 241 ± 114 nM; P > 0.05) or ARG + CHO consumption (Pre: 304 ± 57; Post: 335 ± 116 nM; P > 0.05). During moderate-intensity exercise, the steady-state pulmonary VO2 was not different, relative to the respective placebo conditions, after ARG (PLA: 2,407 ± 318, ARG: 2,422 ± 333 mL min(-1)) or ARG + CHO (CHO: 1,695 ± 304, ARG + CHO: 1,712 ± 312 mL min(-1)) ingestion (P > 0.05). The tolerable duration of severe exercise was also not significantly different (P > 0.05) after ingesting ARG (PLA: 551 ± 140, ARG: 552 ± 150 s) or ARG + CHO (CHO: 457 ± 182, ARG + CHO: 441 ± 221 s). In conclusion, acute dietary supplementation with ARG or ARG + CHO did not alter biomarkers of NO synthesis, O2 cost of exercise or exercise tolerance in healthy subjects.

Musculoskeletal health profile for elite female footballers versus untrained young women before and after 16 weeks of football training.

We investigated the musculoskeletal health profile of elite female football players (ET) in comparison to untrained (UT) young women subjected to 16 weeks of football training (2 × 1 h per week). DXA scans, blood sampling, sprint testing and Flamingo postural balance testing were carried out for 27 Danish national team players and 28 untrained women, with eight women being tested after training. At baseline total BMD and BMC were 13% (1.305 ± 0.050 versus 1.159 ± 0.056 g · cm(-2)) and 23% (3047 ± 235 versus 2477 ± 526 g) higher (P <0.001) and leg BMD and BMC were 24 and 28% higher (P <0.01) in ET than in UT. Resting plasma osteocalcin was 45% higher in ET than in UT (28.8 ± 10.9 versus 19.9 ± 9.9 µg · L(-1), P <0.05). Total lean body mass was 14% higher (50.4 ± 3.3 versus 44.3 ± 4.0 kg) in ET compared with UT, with no difference in total body mass. The number of Flamingo test falls was 56-63% less (P <0.01) and 30 m sprinting speed was 31% faster (P <0.001) in ET than UT. After 16 weeks of football training for UT, lean body mass increased by 1.4 ± 0.5 kg and the number of left leg falls decreased by 29% (P <0.05). No significant changes occurred in BMD or BMC, but plasma osteocalcin increased (P <0.05) by 37%. In summary, elite women footballers have an impressive musculoskeletal health profile compared with untrained controls, but short-term football training seems to reduce the risk of falls and increase bone formation.

Influence of acute dietary nitrate supplementation on 50 mile time trial performance in well-trained cyclists.

Dietary nitrate supplementation has been reported to improve short distance time trial (TT) performance by 1-3 % in club-level cyclists. It is not known if these ergogenic effects persist in longer endurance events or if dietary nitrate supplementation can enhance performance to the same extent in better trained individuals. Eight well-trained male cyclists performed two laboratory-based 50 mile TTs: (1) 2.5 h after consuming 0.5 L of nitrate-rich beetroot juice (BR) and (2) 2.5 h after consuming 0.5 L of nitrate-depleted BR as a placebo (PL). BR significantly elevated plasma [NO(2) (-)] (BR: 472 ± 96 vs. PL: 379 ± 94 nM; P < 0.05) and reduced completion time for the 50 mile TT by 0.8 % (BR: 136.7 ± 5.6 vs. PL: 137.9 ± 6.4 min), which was not statistically significant (P > 0.05). There was a significant correlation between the increased post-beverage plasma [NO(2) (-)] with BR and the reduction in TT completion time (r = -0.83, P = 0.01). Power output (PO) was not different between the conditions at any point (P > 0.05) but oxygen uptake ([Formula: see text]O(2)) tended to be lower in BR (P = 0.06), resulting in a significantly greater PO/[Formula: see text]O(2) ratio (BR: 67.4 ± 5.5 vs. PL: 65.3 ± 4.8 W L min(-1); P < 0.05). In conclusion, acute dietary supplementation with beetroot juice did not significantly improve 50 mile TT performance in well-trained cyclists. It is possible that the better training status of the cyclists in this study might reduce the physiological and performance response to NO(3) (-) supplementation compared with the moderately trained cyclists tested in earlier studies.