Measurement of Physical ActivityObjective Measures

We also measure PA levels to:

• Evaluate current guidelines and trends S• Set recommended levels of physical activity• Investigate the relationship between physical activity and health conditions• Allow research to be conducted on large numbers of people, allowing us to generalise about a wider population.

Objective measures

Often rely on solid data or observations

Predominantly used for the measurement of individuals

Collecting physiological data/movement monitoring can reduce reactivity or social desirability bias

Generally used in small scale studies

Heart Rate Telemetry

Usually a watch

Measure the participants responses to exercise via their heart rate

Typically used to estimate oxygen uptake and therefore energy expenditure

Heart-rate TelemetryAdvantages

Specific physiological parameters

Easy to use

Clear in describing intensity, frequency and duration

Simple, quick data collection

Potential to provide educational information

DisadvantagesLimited use in large numbers due to cost

Some discomfort to participants, especially over extended periods

Use restricted to aerobic activities

Variations in heart rate need to be considered (age, heat, stress, emotions etc)

Calibration needed to each individual

Accelerometers An accelerometer is an electronic device used to assess the acceleration of the body in certain directions.

An accelerometer device is able to provide detail on the frequency, duration and intensity of the physical activity being performed

Provide minute-by-minute information that can be downloaded to a computer for analysis detect movement patterns throughout a day (e.g. how much time a child spends in moderate and/or vigorous physical activity).

AccelerometersAdvantages

Clear in describing intensity, frequency and duration

Non-invasive

Able to provide minute by minute information

Usable for extended periods

Simple, quick data collection

Disadvantages

Limit use in large numbers due to financial cost

Inaccurate measure of some activities (incline walking, weights)

Inability to provide behavioural data (what people are doing during recording)

Pedometers

The original motion sensor for measuring physical activity

Designed to count steps using a metronome that detects vertical movement

Useful to measure distance traveled when you know the stride length of the participant

10000 steps is considered equivalent to meeting the NPAG

PedometersAdvantages

Inexpensive

Non-invasive

Useful in a variety of settings (school, work)

Easy to administer to large groups

Potential to promote behavioural change

Able to measure a common activity

Disadvantages

Some accuracy lost when running/jogging

Possibility to tamper with results

Assessment restricted to walking

Potential to be reactive

Direct Observation

Aims to measure physical activity type, time, place (context)

The most accurate of all objective measures, however the least practical

Direct observation tools include:

BEACHES

SOFIT

SOPLAY

Direct Observation

It is very useful for assessing the activity levels of children.

It can be used in conjunction with other methods, such as accelerometry, to provide a more accurate description of physical activity levels.

It can be time consuming. However, software products have become available that enable observations to be entered, stored and analysed, making the process more useful and appealing.

Direct ObservationAdvantages

Able to provide excellent qualitative and quantitative information.

Able to target specific physical activity behaviours

Able to ease data collection and recording through available software programs

Disadvantages

Training required for observer

Number of participants limited due to labor-intensive data collection

Potentially reactive

Usage limited to a confined setting (playground)

Summary of different PA measurement tools - Objective

Effectiveness of an interventionThe only way we can determine whether a physical activity program increases a person’s physical activity behaviour is to:

• measure their physical activity prior to the introduction of the program (pre-intervention or baseline testing)• repeat the assessment during the intervention or using identical measures at the conclusion of the program (post-test or post-intervention)• repeat the assessment again some time later, such as 12 months after post- intervention. (This is known as follow-up.)