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Chapter4.pptx

Measuring Physical Activity

Chapter 4

In this chapter we will learn about techniques to measure individuals’ physical activity and the strengths and weaknesses of these techniques, fundamentals of physical activity surveillance and sources of public health information on physical activity

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Importance of Fitness Assessments

What are the best ways to measure PA & exercise?

Qualitative values of such techniques

What is needed to measure PA most accurately among individual versus small/large group of people?

What methods should be used in controlled laboratory settings and in free-living populations?

As we already have learned the difference between PA, exercise and physical fitness, have already seen the guidelines developed for all ages, the next thing that comes in mind is what are the best ways to measure PA and exercise? How valid are these measurements? How do we measure individual versus small/large group? What methods should be used in controlled laboratory setting and in free living populations?

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Total energy expenditure (TEE)

Physical Activity Energy Expenditure + The Thermic effect of food + Basal Metabolic Energy Expenditure

Physical Activity Energy Expenditure(PAEE)

The energy expenditure that is specifically the result of PA

The Thermal Effect of Food (TEF)

The amount of energy that is used to digest and metabolize energy that is ingested (food & drink)

Basal Metabolic Energy Expenditure (BMEE)

Energy expended to maintain breathing and circulation at rest

Laboratory Measures of Energy Expenditure

Laboratory based techniques are based on the attempts of assess calorie expenditure or the amount of energy it takes for a person to be physically active, to breath, to circulate blood, or to digest food. Total energy expenditure (TEE) is the sum of physical Activity Energy Expenditure ,the Thermic effect of food and the basal Metabolic Energy Expenditure. Physical Activity Energy Expenditure (PAEE) is defined as the energy expenditure that is specifically the result of PA. The Thermal Effect of Food (TEF) is the amount of energy that is used to digest and metabolize energy that is ingested (food & drink).Basal Metabolic Energy Expenditure (BMEE) is the energy expended to maintain breathing and circulation at rest.

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60-%70% of a person’s TEE is BMEE

10% of TEE is used to digest food

20%-30% is for PAEE

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Most often used laboratory technique

The amount of oxygen used and carbon dioxide expelled is used to estimate energy expenditure

Very good indicator of total energy expenditure in controlled setting

Quantity (frequency, intensity, and duration) and type of PA can be assessed

Methods used

Facemask and gas analysis system

Collecting air samples from the study person present in the room

Indirect Calorimetry

Indirect calorimetry is the most often used method where the amount of oxygen used and carbon dioxide expelled is used to estimate energy expenditure. Because carbon di oxide is a by-product of energy metabolism, it is a very good indicator of total energy expenditure in controlled setting. Energy expenditure is assessed from the collected air samples while the person is in the room. Another way of doing calorimetry is using a facemask and gas analysis system. In this setting the investigators could identify the frequency, intensity, duration and type of PA performed during indirect calorimetry.

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Limitations

Finally , the artificial laboratory setting does not allow people to live normal life, thus jeopardize the public health importance

Although this technique is very accurate, it has some limitations. First, it is relatively expensive because of the special room and diagnostic tools needed for the experiment. Second there could be only one person in one room which makes larger studies tedious and lengthy. Third, equipment needed for this study need to be calibrated often and have risk of breaking. Finally this study does not capture Total energy expenditure in real life as laboratory setting do not allow normal life living observation which is necessary for public health

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Larger studies become tedious and lengthy to carry out

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Equipment could break and needs to be calibrated each time

Expensive

Doubly Labeled Water Technique

Turnover rates of oxygen and hydrogen are measured

Participants are given stable radio isotopes-labeled water

Investigators take baseline measurements

Then measure the excretion of isotopes in the urine samples over the course of one to three weeks.

Urine analyses are done to examine the difference in elimination rates between the labeled oxygen and hydrogen to estimate carbon dioxide production and thus used tp estimate total energy expenditure.

The second laboratory technique that is very accurate measuring in total energy expenditure is the doubly labeled water technique. In this technique the turnover rates of oxygen and hydrogen are measured. In this technique, the participants are given a pre-specified dose of stable radio-isotope labeled water. Investigators take some baseline measurements and then measure the excretion of isotopes in the urine samples over the course of one to three weeks. The difference in elimination rates between the labeled oxygen and hydrogen is used to estimate carbon di oxide production and thus used to estimate total energy expenditure.

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Electronic Measurements To Estimate Energy Expenditure

Accelerometer

Useful in determining total physical activity and in estimating energy expenditure

Attach unit to a waistband and then free to

go about usual activities

Can provide long term data, but cannot

give us the information regarding what type of PA has been done, so walking

is not distinguishable from tennis match.

Pedometer

Useful in measuring walking, jogging, or activities that involve lower body

Measures total steps

Technological advances have minimized recall biases in measuring PA from study participants. Accelerometers have proven to be very useful in determining total physical activity and in estimating energy expenditure. Participants can attach an accelerometer unit to a waistband and then free to go their usual activities. More advance forms are capable of measuring the time spent on PA. Even though accelerometer can provide long term data, it cannot give us the information regarding what type of PA has been done, so walking cannot be distinguishable from tennis match.

Pedometers are another type of electronic monitoring system that is usually very useful in measuring walking, jogging, or activities that involve lower body. Fundamentally it measures total steps and very inexpensive.

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Direct Observation Techniques

Trained observers recognize characteristics of PA and then record what they see for a defined period of time

Observations then converted to estimate of energy expenditure based on the frequency, intensity and duration of the PA/exercise observed

Direct observation techniques have been popular for a long period of time that involves direct observation of the people of places of interest. Trained observers recognize certain characteristics of physical activity and then record what they see for a defined period of time. These observations then can be converted to estimates of energy expenditure based on the frequency, intensity and duration of the PA/exercise observed.

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Self-Report Instrument

Diaries

Interviews

Questionnaire

Historically, self- report was the technique for PA assessment. With self- report, study participants are asked to tell the investigators about their participation in PA. This can be done through interviews, or via questionnaire or diary. Interviewees are asked about the PA for a defined period which could be as short as 24 hours or a bit longer for example for last 7 days or could be sometimes in distant past. Analysis of such data is done to examine the exposure to PA to estimate physical activity energy expenditure that could relates to outcome like risk of heart disease.

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Surveillance In Populations

Microsoft Engineering Excellence

Microsoft Confidential

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Diseases surveillance is the fundamental pillar of public health. Public health surveillance is defined as ongoing systematic collection, analysis, and interpretation of health related data. Public health surveillance involves counting deaths and cases of diseases, monitoring the health effects from certain disease, and to monitor the trends and patterns of the disease in certain population. Physical activity surveillance, a fairly recent surveillance system, has emerged from recent realization that a lack of PA is a major determinant of chronic disease. The overwhelming data results from PA surveillance system faced the research community the challenge of finding correct indicators that will best suit the purpose of finding the associated health outcome of PA.

Public Health Surveillance: counting deaths and cases of diseases, monitoring the health effects from certain disease, and to monitor the trends and patterns of the disease in certain population.

Physical Activity Surveillance: CDC BRFSS

Populations Indicators of Physical Activity