• respiratory measurement
• exercise
• clinical epidemiology

Physical inactivity is the fourth leading risk factor for global mortality across low-income, middle-income and high-income countries.1 Human movement developed for endurance,  yet the technological advancements of the last 50–100 years such as cars, television, computers and the internet have synergistically reduced daily activity. Evolutionary processes, usually occurring over hundreds of thousands to millions of years, have been unable to keep pace with the changing sociology. Human daily energy expenditure, previously stable over the past 3.5 million years, has reduced over the last 50 years concurrent with a dramatic increase in high energy food availability.2

The excess mortality caused by physical inactivity is largely secondary to coronary heart disease (CHD) and other cardiovascular diseases (CVD). A dose–response relationship is apparent whereby ‘moderate’ physical activity is associated with a 20%–25% risk reduction in either CHD or CVD compared with a 30%–35% risk reduction for ‘high’ physical activity.3 Current WHO recommendations for physical activity reflect these statistics advising either at least 150 min of moderate physical activity per week or 75 min of vigorous physical activity and also highlight increased benefit of either 300 min of moderate weekly physical activity or 150 min of vigorous physical activity. Moderate physical activity is typically described around the level of brisk walking whereas running would be categorised as vigorous physical activity. In high-income countries, at least 25%–35% of the population do not achieve these recommendations.

In Thorax, Fuertes and colleagues4 investigate whether levels of physical activity or changes in physical activity are associated with better lung function using data collected from phases II and III of the European Community Respiratory Health Study (ECRHS). They compared spirometric data with vigorous physical activity levels via a self-report questionnaire at two time points approximately 10 years apart in 3912 predominantly young to middle-aged adults. Higher weekly frequency …