You can have as few as 4 and as many as 8 runners on each team.
Please keep in mind that transportation from one leg to another is not provided. If you’re hoping to allow runners to leap frog “ragnar” style, please organize your legs in a way that makes it easy for you to get from one start location to another.
Ideally, each runner on a 4 runner team will have consecutive legs to run. i.e. Runner 1 has legs 1 and 2, Runner 2 has legs 3 and 4, et cetera.