Changing gears: bicycling as the panacea for physical inactivity?

Editorial For some, bicycling is a potential ' solution' to physical inactivity. Active commuting and recreational cycling can theoretically meet a population's need for health-enhancing physical activity. 1 The seductive appeal of cycling relates to its low cost and potentially high population reach. Cycling can be accessed by all ages and social groups, and infrastructure support for cycling is now being built into the new urban development frameworks that include 'active living'. 2 This editorial summarises the health benefi ts and risks of cycling, and describes current controversies and evidence challenges for cycling policy and promotion. The bicycle is a means for individual health-promoting behaviour, is a clinical tool for rehabilitation and a societal tool for contributing to a healthier environment. Here we do not distinguish between the health effects of outdoor and indoor (stationary) cycling, as both can result in similar energy expenditures, but we do classify cycling by purpose into active transport (commuting and utility cycling) and recreational cycling. Physiologically, cycling has advantages over walking: typical commuting cycling intensity is higher (6–8 metabolic equivalents (MET) compared with walking (2.5–3.5 MET). This is important because higher intensity activity yields greater health benefi ts. 3 Until recently there has been promising yet limited evidence on cycling-specifi c health benefi ts. 4 5 A new systematic review 6 identifi ed 16 studies focusing on cycling-specifi c health outcomes. The studies identifi ed a consistent positive relationship between cycling and cardiorespiratory fi tness and functional benefi ts in boys and girls. Furthermore, they demonstrated improvements in cardiorespiratory fi tness and disease risk factor profi les. Several longitudinal epidemiological studies have shown a signifi cant risk reduction for all-cause and cancer mortality and for cardio-vascular disease, colon and breast cancer, and obesity morbidity in middle-aged and older men and women. There are also cycling-associated risks, especially traumatic injuries (requiring acute clinical treatment) and non-traumatic injuries. 7 Next are the potential risks of exposure to poor air quality among cycle commuters. 8 However, a recent analysis has compared the risks and benefi ts, 9 and estimated that the life expectancy gained as a result of increased physical activity was many times larger (3–14 months gained) than the lost life expectancy due to increased air pollution (0.8–40 days lost) and increased traffi c accidents (5–9 days lost), when shifting from a car to cycle commuting in urban settings. There are individual, social and environmental barriers …