Continuous vs Aerobic Postexercise Hypotension

Study Overview
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Brief Summary
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This study examines the effect of obesity and gender on postexercise hypotension with three different randomized exercise protocols or varying intensity. Subjects will be separated into obese and non-obese groups and then further by gender. From there, they will be put through a control, continuous exercise bout, and aerobic interval bout of exercise in a randomized order over three visits. Post exercise blood pressure, as well as other non-invasive cardiac measures will be taken over a 4 hour period.

Detailed Description
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Suboptimal blood pressure, defined as >115/75 mmHg by meta-analysis, exhibits a positive relationship with cardiovascular disease, and is the leading attributable risk factor for death. Research has illustrated that even blood pressure (BP) below the hypertensive levels can contribute to increased vascular mortality. It has been demonstrated that for incremental increases in blood pressure (every 20 mmHg systolic or 10 mmHg diastolic) there is a twofold increase in cardiovascular disease risk. However, mounting evidence suggests that increased fitness and physical activity4 may attenuate the typical age related increase in BP to hypertensive levels. Exercise has been recommended as the first line of treatment in prehypertension and suboptimal BP, and a single bout of exercise (as short at 10 min) has been shown to lower BP for up to 12 hours post. It is this extended bout of postexercise hypotension (PEH) that is thought to contribute to the anti-hypertensive effects of exercise. PEH is well documented in lean and overweight individuals, but there is limited data on PEH in obese populations of both genders. Well characterized for lean and overweight individuals matched for BP, how obese men and women react postexercise is largely unknown and undefined. Only a few published studies exist. A recent meta-analysis examined PEH, but only included subjects with a body mass index of < 31 kg/m2. Only one study to date included exclusively obese subjects (all women), but the authors only demonstrated a PEH 10 min postexercise. To date, we are aware of no published data examining BP matched PEH in centrally obese men and women to that of non-obese men and women. Exercise intensity has been shown to play a role in PEH as well. Data from this lab has demonstrated that short duration, high intensity exercise (aerobic interval exercise -AIE) was able to stimulate a greater duration of PEH when compared to that of a longer duration, moderate intensity exercise (continuous exercise- CE) or even sprint like training. One recently published study examines the effects on AIE training of young, obese women. No significant PEH was found after one hour, however, this time period may not have been long enough to see a significant change in PEH, hence why we are proposing a longer postexercise measurement period. The mechanism for which PEH occurs is unclear. It is thought to be from structural, neurohormonal, and vascular effects of exercise, however, how these variables effect PEH in obese vs non-obese populations has not been studied directly. Using non-invasive methods such as heart rate variability (HRV), cardiac output (CO), and systemic vascular resistance (SRV) will assist us in creating a better idea of the mechanism that which PEH occurs, and any clinical difference central obesity has on these factors. A prior study from this lab found that obese subjects had a heterogeneous response in CO and SVR (increased cardiac output and augmented SVR) when compared to that of non-obese matched subjects, but once more these subjects were only evaluated for 1 hour postexercise.

Official Title
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Postexercise Hemodynamics Compared in Obese and Non-Obese Subjects After Aerobic Interval Training

Conditions
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Postexercise Hypotension

Intervention / Treatment
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* Other: Continuous Exercise
* Other: Aerobic Interval Exercise


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Healthy, inactive (defined as less than 60 min of moderate to vigorous physical activity per week) Men (age 18-45) and non-pregnant women (age 18-55) Normal BMI and waist circumference (18.5- 24.5 kg/m2 and waist <94 cm ) OR obese (BMI > 30kg/m2 and waist >94 cm). normotensive or prehypertensive blood pressure (SBP <140 and DBP <90) according to JNC guidelines. Exclusion Criteria: Subjects over age (men >45, women > 55) Subjects who register more than 60 minutes/week of moderate-to-vigorous physical activity via accelerometer Subjects who classify as hypertensive (SBP >140 or DBP >90) Subjects who answer positively (i.e. yes) on The Physical Activity Readiness Questionnaire (PAR-Q). Subjects with known cardiovascular, pulmonary, renal, or metabolic disease, or are having symptoms of these disease will be excluded, following current American College of Sports Medicine guidelines (ACSM). Current smokers Pregnant women Anyone with contraindications to vigorous exercise will be excluded from the study. -Subjects on medications used for the treatment of symptomatic cardiovascular disease will be excluded.

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 55 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: Treatment
Allocation: Randomized
Intervention Model: Crossover Assignment
Interventional Model Description: Subjects will have a randomized order of treatment (exercise bouts). Each subject will complete all three (control, cont. exercise, aerobic interval), but in a randomized order.
Masking: Single


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| No Intervention: Control<br>Subjects will have no intervention. They will be resting in a chair for the entire length of the visit (4-5 hours) where blood pressure will be taken every 10 min, while other non-invasive cardiac measures are taken (I.E. Cardiac output, systemic vascular resistance, heart rate variability). | |
| Active Comparator: Continuous exercise<br>Subjects will be asked to perform a 45 min exercise bout. After a warmup, the exercise will be 30 minutes at a continuous level. After the exercise period subject will remain in the lab and blood pressure will be measured every 10 minutes for the remainder of the visit (4 hours) while other non-invasive cardiac measures are taken continuously as discussed above. | Other: Continuous Exercise<br>* Subjects will be asked to perform a 45 min exercise bout. 10 minutes will be a warmup (at a work rate associated with 50% heart rate max), 30 minutes at a wattage that elicits 75-80% heart rate max, and a 5 minute cool down period, returning them to approximately 50% heart rate max.<br>* Other names: CE;|
| Experimental: Aerobic Interval Exercise<br>Subjects will be asked to complete a 43 minute exercise session. After a warmup period, the subjects will complete a 4x4 protocol in that they will alternate 4, 4 minute higher intensity exercise bouts with 3, 3 minute lower intensity bouts. After the exercise, subjects will remain in the lab and blood pressure will be measured every 10 minutes for 4 hours, while other non-invasive cardiac measures are taken continuously as discussed above. | Other: Aerobic Interval Exercise<br>* Subjects will be asked to complete a 43 minute exercise session. To warm up, subjects will cycle at a work rate associated with 50% HRmax for 10 minutes. Wattage will then increase and subjects will do four 4-minute intervals at a work rate associated with 90%-95% HRmax, separated by 3 minutes of active recovery at a work rate associated with 50% HRmax. Subjects will be given a 5-minute cool-down period at a work rate associated with 50% HRmax.<br>* Other names: AIE;|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Postexercise Blood pressure | Central and peripheral blood pressure (systolic and diastolic) taken via Oscar 2 device. | Postexercise- every ten minutes for four hours post exercise session | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Heart Rate Variability | Heart rate variability (taken via polar monitor) | until study completion- up to 2 years | 
| Cardiac Output- non-invasive | Non-invasive: taken via physioflow device | until study completion- up to 2 years | 
| Systemic Vascular Resistance | Non-Invasive: Taken via physioflow device | until study completion- up to 2 years | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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hemodynamics, exercise