For most people, light physical activity makes up the bulk of their daily physical activity. Yet government guidelines focus almost exclusively on moderate to vigorous-intensity physical activity. The difficulty of measuring a person’s lightintensity physical activity largely explains this disconnect. It is not possible to measure light physical activity with a questionnaire. The amount of light-intensity physical activity a person thinks they have done bears almost no resemblance to what they have actually done. This means it has been difficult to study the effects of light-intensity physical activity on long-term health.