Objective Physical Activity Assesment in Postmenopausal Women

Study Overview
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Brief Summary
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The purpose of this study is to accurately assess weekly physical activity levels of postmenopausal women using lactate thresholds to individualize the accelerometer cut-points.

Detailed Description
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This observational study aims to accurately assess weekly physical activity levels of postmenopausal women using lactate thresholds to individualize the accelerometer cut-points. Postmenopausal women will be recruited from local advertisements in public health centers. Each woman will perfom on different days a progressive discontinuous submaximal walking-running test and several constant speed tests wearing an accelerometer to identify the individual lactate threshold (LT), the maximal lactate steady state (MLSS) and the corresponding accelerometer activity counts/min (cpm). Participants then will wear an actigraph accelerometer (wGT3X-BT) for seven days. Linear regression equations will be developed for each participant to determine accelerometer activity counts for each intensity level: 1) sedentary behaviour (<200 cpm), 2) light intensity (200 cpm to activity counts at LT), 3) moderate intensity (activity counts between LT and MLSS) and 4) vigorous intensity (activity counts >MLSS). Physical activity levels will be measured using both, individualized approach and Sasaki, Jonh and Freedson´s (2011) absolute cut-points obtained through walking and running activities eliciting 3-6 MET intensities (2689-6166 cpm), considering it a moderate effort.

Official Title
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The Use of Lactate Thresholds to Individualize Accelerometer Cut-points and Objectively Assess Physical Activity Levels in Postmenopausal Women

Conditions
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Primary Prevention

Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Age between 50 and 70 years Surgical or natural menopause (no menstrual periods during at least the last 6 months) Exclusion Criteria: Body mass index less than 39kg/m2 (obesity class III) Osteoporosis Presence of low-trauma fractures or severe arthrosis at hip, knees or feet Functional limitation to walk fast or altered gait patters and instability Presence of any chronic disesase that would impair the cardiovascular (e.g. myocardial infarction, stroke, chronic heart failure), musculoskeletal (osteoporosis, low-trauma fractures) and respiratory systems (COPD) or any disease or medication known to affect bone metabolism (glucocorticoids)

Ages Eligible for Study
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Minimum Age: 50 Years
Maximum Age: 70 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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What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Time spent in moderate-to-vigorous physical activities | The time spent in moderate-to-vigorous physical activities during a week (The participants have to wear an accelerometer attatched at the hip on an elastic belt for a period of 7 days) | 1 week | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| accelerometer intensity cut-points | accelerometer activity counts corresponding to each woman´s lactate thresholds will determine each intensity level (These thresholds are determined on the walking-running tests performed on different days with a minimum of one week in between. These tests are independent, they are performed at constant speed during 20min to determine the highest speed at which the lactate concentration remains in a steady state between the minute 10 and 20 of the test) | an average of 1 month | 
| Number of vertical acceleration peaks during the day | raw acceleration data will be measured to describe daily exposure to potentially osteogenic vertical impacts (The participants have to wear an accelerometer attatched at the hip on an elastic belt for a period of 7 days) | 1 week | 
| aerobic fitness | determination of the speeds corresponding to the lactate thresolds during the walking-running test | an average of 1 month | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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accelerometry, aerobic fitness, metabolic thresholds, moderate to vigorous physical activity