The missing middle: Exploring light-intensity physical activity and how it relates to health among adults in Canada

Background: The health benefits of moderate-to-vigorous physical activity (MVPA) are well established, as are the detrimental impacts of excess sedentary time. Less is known about the benefits of activity undertaken at intensities between sedentary and moderate. This study examines how average daily minutes spent in each movement intensity and average daily steps accumulated in each intensity band varied across population groups by age and sex. It also examines the associations between movement intensities and health indicators. Data and methods: The Actical accelerometer subsample data, household data and clinic data of the Canadian Health Measures Survey (2007 to 2019) were used for this analysis. Light-intensity physical activity (LPA) was subdivided into three intensities based on tertiles: low, mid and high. Results: Females and older adults accumulated fewer minutes of physical activity and fewer steps than their counterparts, in mid LPA, high LPA, and MVPA. After adjusting for MVPA and covariates, minutes and steps spent in mid LPA were significantly associated with reduced odds of having cardiovascular disease (CVD), two or more chronic conditions, and poor or fair general health, while minutes and steps in high LPA were significantly associated with reduced odds of having CVD. Interpretation: While spending time in MVPA is positive for health, this study suggests that increasing daily minutes and steps in higher intensity LPA is also associated with health benefits. This study is consistent with previous studies that show that all movement is beneficial, including LPA, particularly when it replaces sedentary behaviour.