We Walk: Impact of Exercise Dose on Health Outcomes Among Women Ages 60-75

Study Overview
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Brief Summary
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The overall goal is to determine whether any energy expenditure compensation in response to 16 weeks of aerobic exercise at a higher-dose is greater compared to a lower-dose intervention in older women, and to begin to investigate underlying physiological mechanisms that influence energy expenditure changes in older women.

Detailed Description
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The overall goal is to determine whether any energy expenditure compensation in response to 16 weeks of aerobic exercise at a higher-dose is greater compared to a lower-dose intervention in older women, and to begin to investigate underlying physiological mechanisms that influence energy expenditure changes in older women. Changes in all components of energy expenditure, as well as concentrations of plasma leptin and serum free T3, in response to the two different exercise programs (14 and 8 kcal/kg body weight weekly, 60-65% VO2max, 4 days/wk) will be compared in older, non-obese women (60-75 yrs, BMI=18-30 kg/m2). Specific Aim 1: To determine whether differential changes in total daily energy expenditure and its components occur in older women in response to two exercise programs of different doses. State-of-the-art methods will be used (total daily energy expenditure by doubly labeled water; non-exercise activity thermogenesis using Physical Activity Monitoring System; resting metabolic rate and thermic effect of food via indirect calorimetry). Primary Hypothesis: Due to a greater decline in NEAT, women will exhibit a smaller increase in total daily energy expenditure in response to the higher-dose, compared to the lower-dose, exercise program, despite greater increases in resting metabolic rate and thermic effect of food. Specific Aim 2: To explore whether differential changes occur in plasma leptin and serum free triiodo-L-thyronine (free T3) concentrations in older women in response to 16-week aerobic exercise programs of two different doses. We hypothesize that in response to the higher-dose exercise program, women will exhibit larger decreases in plasma leptin and serum free T3 concentrations, compared to the lower-dose exercise program. We will also determine whether women exhibit greater improvements in plasma lipids, insulin sensitivity (using homeostasis model assessment, HOMA, score), blood pressure, and aerobic fitness in response to the higher-dose, compared to the lower-dose, exercise program.

Official Title
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We Walk - Energy Expenditure and Health Outcomes in Older, Sedentary Women.

Conditions
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Condition

Intervention / Treatment
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* Behavioral: Low Dosage
* Behavioral: High Dosage


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: BMI 18-30 Sedentary (exercising less than 20 minutes no more than 3 times per week) Non-smoking Weight stable (+/- 5%) over past 3 months Exclusion Criteria: Self-reported cardiovascular disease Additional self-reported medical conditions Medications known to affect metabolism Excess caffeine use Self-reported contradictions according to ACSM Unwillingness to provide informed consent

Ages Eligible for Study
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Minimum Age: 60 Years
Maximum Age: 75 Years

Sexes Eligible for Study
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Female

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: Supportive Care
Allocation: Randomized
Intervention Model: Parallel Assignment
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Low Dosage<br>Exercise dose of 8kcal/kg/week | Behavioral: Low Dosage<br>* Exercise dose of 8kcal/kg/week<br>|
| Experimental: High Dosage<br>Exercise dose 14kcal/kg/week | Behavioral: High Dosage<br>* Exercise dose of 14kcal/kg/week<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Change from baseline total daily energy expenditure and its components (resting metabolic rate, thermic effect of food, non-exercise activity thermogenesis)in 4 months |  | Baseline (pre-intervention); 4 months (post-intervention) | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Change from baseline plasma leptin and serum free triiodo-L-thyronine (free T3) concentrations in 4 months |  | Baseline (pre-intervention); 4 month (post-intervention) |