Warm-up and gauge pace with one rep @ 85-90% effort over the predetermined interval of time.
Recover fully (8:00-12:00).
Attempt rep @ max effort, calling elapsed time, and mark the distance reached.
Record distance for each athlete.
Repeat session 2-4 weeks later, setting markers at previously achieved distances.
Spiked up.
One athlete at a time — they should be competing with themselves, not (directly) against teammates.