Orienteering is a running navigation sport, where participants use a detailed map to visit a series of check-points (controls) as quickly as possible. The route is unmarked, and runners are free to choose their own way between check points. Top competitors are highly-trained athletes, capable of racing at high speed through rough forested terrain. Besides specific navigation-technique and terrain exercises, orienteers generally train like long-distance runners. Orienteering races can be any length, but the most common formats have winning times ranging from 12-90 minutes. Top runners' pace averages around 4-5 min/km in the forest but can be as quick as 3 min/km in sprint events, where there is often more running on faster surfaces like grass, trails, and roads.