Lail et al. BMC Public Health 2011, 11:148 http://www.biomedcentral.com/1471-2458/11/148 A significant difference in NTW between dog-owners and non-owners was not found in our study, but pre- vious work has found that dog-owners are less likely to walk for transportation compared to non-owners [30]. The limited difference in NTW among dog-owners compared with non-owners could be attributable to a lack of dog-friendly parks, shops, and other commercial destinations within walking distance of home [33]. Allowing people to bring their dogs to work could be beneficial to owners as well as to non-owners [34], but dogs are not generally allowed in workplaces unless they are designated as service animals, such as seeing- eye dogs. Consequently, adults who walk to work gen- erally leave their dogs at home. In addition, even though dogs are allowed on public transportation in the City of Calgary, the dog-owners in our sample who commute by public transit would have few options for dog care at or near businesses, workplaces, or educa- tional institutions, thus impeding them from walking with their dog to bus stops or commuter train stations located within their neighbourhood. This study contributes to the literature on determi- nants of physical activity by showing that dog-owner- ship contributes to walking for recreation in residential neighbourhoods despite seasonal fluctuations, yet has several limitations. While we used previously-tested items for capturing walking [26,27], self-reported phy- sical activity is nevertheless affected by recall and memory bias [35]. The use of objective measures of physical activity (i.e., pedometers and accelerometers) in future research could overcome this limitation. About 45% of our original sample was lost to follow-up or was missing data, which may have introduced a bias to our sample [7]. The reasons why we found higher levels of NRW among dog-owners in the winter com- pared with the summer, furthermore, are not evident. One possibility is that during summer months owners and their dogs may be more likely to undertake recrea- tional activities at destinations or in open spaces located outside their immediate neighbourhood (i.e., mountains, provincial parks, lakes) rather than close to home. Another possibility, is that in the summer months, dog-owners living in detached or semi- detached housing may be inclined to unleash their dogs in the backyard, rather than taking them out for walks in the neighbourhood. Future research using qualitative and quantitative methods is needed to bet- ter understand the interrelationships between dog- ownership, seasonality and physical activity behaviour. Conclusions Health professionals should discuss but not prescribe dog-ownership as a way to promote physical and mental health via regular physical activity. Dog-ownership may Page 6 of 7 provide a social support that encourages walking, there- fore, initiatives to help shape a similar type of social support, such as dog-sharing programs, may help increase physical activity [36,37]. Furthermore, as not all dog-owners regularly walk their dog [28], destinations such as cafes, shops, and parks with dog-friendly attri- butes could encourage more walking among this group [38]. Dog-ownership status should be considered when designing and assessing interventions to increase year- round physical activity participation. Abbreviations NRW: Neighbourhood-based recreational walking; NTW: Neighbourhood- based transportation walking. Acknowledgements PL was supported by a Queen Elizabeth II Scholarship from the Province of Alberta, a research assistantship from an Alberta Innovates - Health Solutions Establishment Grant to MR, and a University of Calgary Faculty of Medicine Tuition Bursary. GRM was supported by a Canadian Institutes of Health Research Bisby Postdoctoral Fellowship. MR was supported by a New Investigator Award from the Canadian Institutes of Health Research and a Population Health Investigator Award from Alberta Innovates - Health Solutions (funded by the Alberta Heritage Foundation for Medical Research Endowment). Funding to carry out the research came from an Alberta Innovates - Health Solutions Establishment Grant (sole investigator, MR) and a Canadian Institutes of Health Research Operating Grant (principal investigator, Alan Shiell). Authors’ contributions GRM and MR conceived the current study. PL led the drafting of the manuscript with input from GRM and MR. 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