Background Community-based 5 kilometre running/walking events known as ‘parkruns’, organised by volunteers using web based infrastructure maintained by a national charity, are a rapidly growing international phenomenon. Every Saturday morning over 100 000 people take part in a ‘parkrun’ in the UK, with 1200 participating each week in the city of Sheffield. Despite increasing support for events to be set up in public parks in more deprived neighbourhoods, individuals living in less affluent areas are less likely to participate. Better understanding is needed of what makes events accessible and attractive to those from poorer neighbourhoods if there is to be a positive impact on inequalities in physical activity and associated wellbeing. This study explored differences in participation and factors that affect participation across the five Sheffield parkrun events.

Methods We collected qualitative and quantitative information from routine data sources, from the event websites and from social media and pairs of researchers conducted structured observations at each of five events at different locations across the city. The routine information on participation was used to compare the characteristics of participants for the five events. The qualitative findings were analysed thematically to identify similarities and differences between the different events which might explain significant differences in numbers and characteristics of participants across the five different events.

Results Index of multiple deprivation was the main predictor of attendance numbers, with weekly attendance varying from 584 (most affluent location) to 63 (most deprived location). Men outnumbered women (57% vs 43%) and ethnic diversity was low across all events. Significant differences in participant experience were observed between the larger and smaller events in terms of the competitive ethos, degree of anonymity, sense of community and social engagement. There appeared to be a trade-off with larger events offering anonymity and a spirt of competition, whilst smaller events seemed to encourage a more supportive and friendly social experience for participants.

Conclusion Patterns of participation suggest that mass weekly community events of this nature are, whilst likely to provide health benefits to the population as a whole, also likely to be responsible for significant intervention generated inequalities in uptake of opportunities for physically active recreation. Current efforts to increase access to opportunities for physical activity in deprived communities may need to consider carefully how to identify effective ways to attract more participants whilst preserving the perceived benefits of smaller events that promote community ownership and engagement.