The association of natural elements and trail use by adults.

We used the System for Observing Play and Recreation in Communities to examine the association between variations in natural elements (ie, season, weather, and temperature) and adults' use of a rail-trail in South Carolina (2006-2009). Most (62%) of the 4,468 trail users observed were walkers; 38% were observed participating in vigorous physical activity. Adults were most often observed using the trail during the summer (32%), sunny weather (78%), and moderate temperatures (54%). When promoting trail use among adults, natural elements should be considered.