Dietary nitrate supplementation does not influence thermoregulatory or cardiovascular strain in older individuals during severe ambient heat stress

We tested the hypothesis that dietary nitrate (NO3−)-rich beetroot juice (BR) supplementation could partially offset deteriorations in O2transport and utilization and exercise tolerance after blood donation. Twenty-two healthy volunteers performed moderate-intensity and ramp incremental cycle exercise tests prior to and following withdrawal of ∼450 ml of whole blood. Before donation, all subjects consumed seven 70-ml shots of NO3−-depleted BR [placebo (PL)] in the 48 h preceding the exercise tests. During the 48 h after blood donation, subjects consumed seven shots of BR (each containing 6.2 mmol of NO3−, n = 11) or PL ( n = 11) before repeating the exercise tests. Hemoglobin concentration and hematocrit were reduced by ∼8–9% following blood donation ( P < 0.05), with no difference between the BR and PL groups. Steady-state O2uptake during moderate-intensity exercise was ∼4% lower after than before donation in the BR group ( P < 0.05) but was unchanged in the PL group. The ramp test peak power decreased from predonation (341 ± 70 and 331 ± 68 W in PL and BR, respectively) to postdonation (324 ± 69 and 322 ± 66 W in PL and BR, respectively) in both groups ( P < 0.05). However, the decrement in performance was significantly less in the BR than PL group (2.7% vs. 5.0%, P < 0.05). NO3−supplementation reduced the O2cost of moderate-intensity exercise and attenuated the decline in ramp incremental exercise performance following blood donation. These results have implications for improving functional capacity following blood loss.

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Increased Air Velocity Reduces Thermal and Cardiovascular Strain in Young and Older Males during Humid Exertional Heat Stress

Journal of Occupational and Environmental Hygiene ◽

10.1080/15459624.2015.1029613 ◽

2015 ◽

Vol 12 (9) ◽

pp. 625-634 ◽

Cited By ~ 2

Author(s):

Heather E. Wright Beatty ◽

Stephen G. Hardcastle ◽

Pierre Boulay ◽

Andreas D. Flouris ◽

Glen P. Kenny

Keyword(s):

Heat Stress ◽

Air Velocity ◽

Exertional Heat Stress ◽

Cardiovascular Strain ◽

Older Males

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Abstract P134: Preliminary Data: Dietary Nitrate Supplementation Does Not Extend Dry Static Apnea Or Wingate Performance

Circulation ◽

10.1161/circ.143.suppl_1.p134 ◽

2021 ◽

Vol 143 (Suppl_1) ◽

Author(s):

Colin Carriker ◽

Phillip Armentrout ◽

Sarah Levine ◽

James Smoliga

Keyword(s):

Power Output ◽

Preliminary Data ◽

Repeated Measures ◽

Peak Power ◽

Hold Time ◽

Wingate Test ◽

Peak Power Output ◽

Breath Hold ◽

Dietary Nitrate ◽

Nitrate Supplementation

Introduction: Previous studies have examined dietary nitrate supplementation and its effects on dry static apnea, and peak power. Dietary nitrate supplementation has been found to increase maximal apnea and peak power output. The purpose of this study was to determine the effects of beetroot juice on dry static apnea and Wingate performance. Hypothesis: Dietary nitrate will improve maximal breath hold time and peak power output. Dietary nitrate will improve tolerance to CO2, thereby improving maximal breath hold time and anaerobic capacity. Methods: In a randomized, double-blind, counterbalanced study, five healthy males (20.4±0.89 years) visited the lab on 3 separate occasions each separated by one week. Visit 1 served as a Wingate and breath hold familiarization visit. Prior to visits 2 and 3 participants were instructed to drink a beverage either a placebo (negligible nitrate content, PL) or dietary nitrate rich beverage (12.4 mmol nitrate, NIT) during the 4 days leading up to their next visit. Visits 2 and 3 consisted of two submaximal breath holds (80% of maximal determined during visit 1), with 2 minutes of rest between and three minutes of rest preceding the final breath hold for maximal duration. Finally, participants completed a standardized 10-minute warmup on the cycle ergometer before completing a 30-second maximal effort Wingate test. Results: A linear mixed effects model was used to determine whether treatment (NIT vs. PL) was associated with differences in VCO2 or PetCO2. Time (0, 10, 20, 30 min post-breath hold) and Treatment both served as repeated measures. Models were developed using multiple repeated measures covariance matrix structures, and the model with the lowest AIC was chosen as the final model. The interaction between time and treatment was included in the original models, and was removed if it was not statistically significant. Time was a statistically significant factor for VCO2 and PetCO2 (p < 0.001). Treatment, and the Time x Treatment interaction was not significant for either variable. No differences between NIT and PL were observed during the Wingate test for either time to peak power (5.02±2.45 and 6.2±2.43 sec, respectively) or maximal power (9.73±1.01 and 9.72±1.03 watts/kg, respectively) and fatigue index (49.42±14.98 and 47.30±6.99 watts/sec, respectively). Conclusion: Preliminary data indicates that in a general population four days of dietary nitrate supplementation may not improve breath hold time, tolerance to carbon dioxide in the lungs, or Wingate performance.

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Dietary nitrate supplementation in COPD: An acute, double-blind, randomized, placebo-controlled, crossover trial☆

Nitric Oxide ◽

10.1016/j.niox.2014.12.010 ◽

2015 ◽

Vol 44 ◽

pp. 105-111 ◽

Cited By ~ 41

Author(s):

Conor P. Kerley ◽

Kathleen Cahill ◽

Kenneth Bolger ◽

Aisling McGowan ◽

Conor Burke ◽

...

Keyword(s):

Crossover Trial ◽

Double Blind ◽

Dietary Nitrate ◽

Nitrate Supplementation

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The Effect of Dietary Nitrate Supplementation on Physiology and Performance in Trained Cyclists

International Journal of Sports Physiology and Performance ◽

10.1123/ijspp.2016-0202 ◽

2017 ◽

Vol 12 (5) ◽

pp. 684-689 ◽

Cited By ~ 9

Author(s):

Joseph A. McQuillan ◽

Deborah K. Dulson ◽

Paul B. Laursen ◽

Andrew E. Kilding

Keyword(s):

Time Trial ◽

Crossover Design ◽

Moderate Intensity ◽

Beetroot Juice ◽

Double Blind ◽

Dietary Nitrate ◽

Performance Time ◽

Exercise Economy ◽

Nitrate Supplementation ◽

And Performance

Purpose:To determine the effect of dietary nitrate (NO3 –) supplementation on physiology and performance in well-trained cyclists after 6–8 d of NO3 – supplementation.Methods:Eight competitive male cyclists (mean ± SD age 26 ± 8 y, body mass 76.7 ± 6.9 kg, VO2peak 63 ± 4 mL · kg–1 · min–1) participated in a double-blind, placebo-controlled, crossover-design study in which participants ingested 70 mL of beetroot juice containing ~4 mmol NO3 – (NIT) or a NO3 –-depleted placebo (PLA), each for 8 d. Replicating pretreatment measures, participants undertook an incremental ramp assessment to determine VO2peak and first (VT1) and second (VT2) ventilatory thresholds on d 6 (NIT6 and PLA6), moderate-intensity cycling economy on d 7 (NIT7 and PLA7), and a 4-km time trial (TT) on d 8 (NIT8 and PLA8).Results:Relative to PLA, 6 d of NIT supplementation produced unclear effects for VO2peak (mean ± 95% confidence limit: 1.8% ± 5.5%) and VT1 (3.7% ± 12.3%) and trivial effects for both VT2 (–1.0% ± 3.0%) and exercise economy on d 7 (–1.0% ± 1.6%). However, effects for TT performance time (–0.7% ± 0.9%) and power (2.4% ± 2.5%) on d 8 were likely beneficial.Conclusions:Despite mostly unclear outcomes for standard physiological determinants of performance, 8 d of NO3 – supplementation resulted in likely beneficial improvements to 4-km TT performance in well-trained male endurance cyclists.

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Dietary interventions for fetal growth restriction - therapeutic potential of dietary nitrate supplementation in pregnancy

The Journal of Physiology ◽

10.1113/jp273331 ◽

2017 ◽

Vol 595 (15) ◽

pp. 5095-5102 ◽

Cited By ~ 10

Author(s):

Elizabeth Cottrell ◽

Teresa Tropea ◽

Laura Ormesher ◽

Susan Greenwood ◽

Mark Wareing ◽

...

Keyword(s):

Fetal Growth ◽

Fetal Growth Restriction ◽

Therapeutic Potential ◽

Growth Restriction ◽

Dietary Interventions ◽

Dietary Nitrate ◽

Nitrate Supplementation ◽

In Pregnancy

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Acute beetroot juice supplementation on sympathetic nerve activity: a randomized, double-blind, placebo-controlled proof-of-concept study

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.00163.2017 ◽

2017 ◽

Vol 313 (1) ◽

pp. H59-H65 ◽

Cited By ~ 28

Author(s):

Karambir Notay ◽

Anthony V. Incognito ◽

Philip J. Millar

Keyword(s):

Nitric Oxide ◽

Blood Pressure ◽

Sympathetic Outflow ◽

Beetroot Juice ◽

Proof Of Concept ◽

Burst Frequency ◽

Double Blind ◽

Dietary Nitrate ◽

Nitrate Supplementation ◽

Central Sympathetic Outflow

Acute dietary nitrate ([Formula: see text]) supplementation reduces resting blood pressure in healthy normotensives. This response has been attributed to increased nitric oxide bioavailability and peripheral vasodilation, although nitric oxide also tonically inhibits central sympathetic outflow. We hypothesized that acute dietary [Formula: see text] supplementation using beetroot (BR) juice would reduce blood pressure and muscle sympathetic nerve activity (MSNA) at rest and during exercise. Fourteen participants (7 men and 7 women, age: 25 ± 10 yr) underwent blood pressure and MSNA measurements before and after (165–180 min) ingestion of 70ml high-[Formula: see text] (~6.4 mmol [Formula: see text]) BR or [Formula: see text]-depleted BR placebo (PL; ~0.0055 mmol [Formula: see text]) in a double-blind, randomized, crossover design. Blood pressure and MSNA were also collected during 2 min of static handgrip (30% maximal voluntary contraction). The changes in resting MSNA burst frequency (−3 ± 5 vs. 3 ± 4 bursts/min, P = 0.001) and burst incidence (−4 ± 7 vs. 4 ± 5 bursts/100 heart beats, P = 0.002) were lower after BR versus PL, whereas systolic blood pressure (−1 ± 5 vs. 2 ± 5 mmHg, P = 0.30) and diastolic blood pressure (4 ± 5 vs. 5 ± 7 mmHg, P = 0.68) as well as spontaneous arterial sympathetic baroreflex sensitivity ( P = 0.95) were not different. During static handgrip, the change in MSNA burst incidence (1 ± 8 vs. 8 ± 9 bursts/100 heart beats, P = 0.04) was lower after BR versus PL, whereas MSNA burst frequency (6 ± 6 vs. 11 ± 10 bursts/min, P = 0.11) as well as systolic blood pressure (11 ± 7 vs. 12 ± 8 mmHg, P = 0.94) and diastolic blood pressure (11 ± 4 vs. 11 ± 4 mmHg, P = 0.60) were not different. Collectively, these data provide proof of principle that acute BR supplementation can decrease central sympathetic outflow at rest and during exercise. Dietary [Formula: see text] supplementation may represent a novel intervention to target exaggerated sympathetic outflow in clinical populations. NEW & NOTEWORTHY The hemodynamic benefits of dietary nitrate supplementation have been attributed to nitric oxide-mediated peripheral vasodilation. Here, we provide proof of concept that acute dietary nitrate supplementation using beetroot juice can decrease muscle sympathetic outflow at rest and during exercise in a normotensive population. These results have applications for targeting central sympathetic overactivation in disease.

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The Effects of Dietary Nitrate Supplementation on Time Trial Performance in Trained Cyclists

Medicine & Science in Sports & Exercise ◽

10.1249/01.mss.0000402381.16199.26 ◽

2011 ◽

Vol 43 (Suppl 1) ◽

pp. 854

Author(s):

Chris Easton ◽

Dylan Merkett ◽

Chelsea Stock ◽

Fergal Grace

Keyword(s):

Time Trial ◽

Dietary Nitrate ◽

Time Trial Performance ◽

Nitrate Supplementation ◽

Trial Performance

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A Field Evaluation of Construction Workers’ Activity, Hydration Status, and Heat Strain in the Extreme Summer Heat of Saudi Arabia

Annals of Work Exposures and Health ◽

10.1093/annweh/wxaa029 ◽

2020 ◽

Vol 64 (5) ◽

pp. 522-535 ◽

Cited By ~ 1

Author(s):

Mohammed Al-Bouwarthan ◽

Margaret M Quinn ◽

David Kriebel ◽

David H Wegman

Keyword(s):

Heart Rate ◽

Saudi Arabia ◽

Heat Stress ◽

Heat Exposure ◽

Heat Strain ◽

Construction Workers ◽

Hydration Status ◽

Summer Heat ◽

Cardiovascular Strain ◽

Indoor And Outdoor

Abstract Objectives Assess the impact of summer heat exposure (June–September) on residential construction workers in Al-Ahsa, Saudi Arabia by evaluating (i) heart rate (HR) responses, hydration status, and physical workload among workers in indoor and outdoor construction settings, (ii) factors related to physiological responses to work in hot conditions, and (iii) how well wet-bulb globe temperature-based occupational exposure limits (WBGTOELs) predict measures of heat strain. Methods Twenty-three construction workers (plasterers, tilers, and laborers) contributed 260 person-days of monitoring. Workload energy expenditure, HR, fluid intake, and pre- and postshift urine specific gravity (USG) were measured. Indoor and outdoor heat exposures (WBGT) were measured continuously and a WBGTOEL was calculated. The effects of heat exposure and workload on heart rate reserve (HRR), a measure of cardiovascular strain, were examined with linear mixed models. A metric called ‘heat stress exceedance’ (HSE) was constructed to summarize whether the environmental heat exposure (WBGT) exceeded the heat stress exposure limit (WBGTOEL). The sensitivity and specificity of the HSE as a predictor of cardiovascular strain (HRR ≥30%) were determined. Results The WBGTOEL was exceeded frequently, on 63 person-days indoors (44%) and 91(78%) outdoors. High-risk HRR occurred on 26 and 36 person-days indoors and outdoors, respectively. The HSE metric showed higher sensitivity for HRR ≥30% outdoors (89%) than indoors (58%) and greater specificity indoors (59%) than outdoors (27%). Workload intensity was generally moderate, with light intensity work more common outdoors. The ability to self-pace work was associated with a lower frequency of HRR ≥30%. USG concentrations indicated that workers began and ended their shifts dehydrated (USG ≥1.020). Conclusions Construction work where WBGTOEL is commonly exceeded poses health risks. The ability of workers to self-pace may help reduce risks.

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