Exercise Fatiguability in Older Adults: The Protective Effects of Dietary Nitrate Supplementation

Study Overview
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Brief Summary
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Vascular and skeletal muscle function decline with age and are associated with decreased nitric oxide (NO) bioavailability. Dietary nitrate supplementation in the form of beet root juice increases NO bioavailability and improves exercise tolerance in younger adults, yet its effects on fatigability in older adults are largely unknown. The proposed research will investigate the impact of increased NO bioavailability on vascular function, skeletal muscle bioenergetics, and fatigability in older (≥65 yrs) men and women.

Official Title
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Exercise Fatiguability in Older Adults: The Protective Effects of Dietary Nitrate Supplementation

Conditions
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Aging

Intervention / Treatment
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* Dietary Supplement: Beetroot Juice
* Other: Placebo Beetroot Juice


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Healthy men and women ≥ 60 years old Exclusion Criteria: body mass index ≥40 kg/m2; type 1 or type 2 diabetes or HbA1c >6.5% uncontrolled hypertension; active cancer, cancer in remission, or having received treatment for any form of cancer in the previous five years; coronary artery disease; cardiovascular disease (e.g., PAD, PVD); abnormal and untreated thyroid function; chronic and/or regular nonsteroidal anti-inflammatory drugs (NSAID) consumption, tobacco use (includes smoking); any condition that presents a limitation to exercise (e.g., severe arthritis, COPD, neuromuscular disorder, moderate or severe cognitive impairment, Alzheimer's Disease, severe untreated sleep apnea).

Ages Eligible for Study
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Minimum Age: 60 Years
Maximum Age: 90 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Basic Science
Allocation: Randomized
Intervention Model: Crossover Assignment
Masking: Triple


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Active Comparator: Beetroot Juice<br>The subject will ingest 140mL of a nitrate-rich beetroot juice each day for 7 consecutive days. | Dietary Supplement: Beetroot Juice<br>* 7 days of 140 mL per day of beetroot juice<br>* Other names: James White Drinks Beet It Sport 400;|
| Placebo Comparator: Placebo Beetroot Juice<br>The subject will ingest 140mL of a placebo (nitrate-depleted) beetroot juice each day for 7 consecutive days. | Other: Placebo Beetroot Juice<br>* 7 days of 140 mL per day of placebo beetroot juice<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Change in fatigability of the knee extensor muscles with beetroot juice supplementation | Fatigability will be quantified as the reduction in limb muscle power output during a 4-minute dynamic fatiguing exercise task using a dynamometer. Fatigability after 7 days of beetroot juice supplementation will be compared with fatigability after 7 days of placebo supplementation, with the outcome measure being the change (or difference) between these two supplementation conditions. | Day 8 (after 7 days of placebo supplementation) and day 29 (after 14 days of a washout period with no supplementation plus 7 days of beetroot juice supplementation) | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Change in femoral artery blood flow with beetroot juice supplementation | Femoral artery blood flow will be quantified as the change in femoral artery blood flow during a 4-minute dynamic fatiguing exercise task using a ultrasonography. Femoral artery blood flow after 7 days of beetroot juice supplementation will be compared with Femoral artery blood flow after 7 days of placebo supplementation, with the outcome measure being the change (or difference) between these two supplementation conditions. | Day 8 (after 7 days of placebo supplementation) and day 29 (after 14 days of a washout period with no supplementation plus 7 days of beetroot juice supplementation) | 
| Change in muscle efficiency with beetroot juice supplementation | Muscle efficiency will be quantified as the ATP cost of contraction using phosphorus magnetic resonance spectroscopy (P-MRS). Muscle efficiency after 7 days of beetroot juice supplementation will be compared with muscle efficiency after 7 days of placebo supplementation, with the outcome measure being the change (or difference) between these two supplementation conditions. | Day 8 (after 7 days of placebo supplementation) and day 29 (after 14 days of a washout period with no supplementation plus 7 days of beetroot juice supplementation) |