At a population level:

• To understand the dose-response relationship between PA/SB and health outcomes
• To identify current and changing activity levels within populations
• To monitor compliance with public health guidelines
• To identify the biological, psychological and environmental factors that influence PA/SB
• To determine the effectiveness of interventions

At the individual level:

• To identify current activity levels
• To detect change in an individual’s behaviour
• Feedback, motivation and goal setting