For each run use the build up to approach sprint speed and maintain sprint through the rest of the run. After the run, take an easy walk for the distance you just ran. For example, after running 50m, walk 50m. The goal is to stay relaxed enough to either build speed or never lose speed.
-50m
-75m
-100m
-150m
-200m
-150m
-100m
-75m
-50m