Set up an ultimate field (x 70 yards field proper, x 25 yard end zones, x 40 yards wide). Keep water close by.
A ‘sprint’ is 85-100% of max speed; go at 100% effort (or max speed) for distances 40 yards or shorter (the short side of the field), go 90-95% for 60-100 yards (the long side), and 85-95% for 100-400 yards (2, 3, or 4 sides of the field).