Sprinters should limit distance running during training. Sprinters need to activate and train the bulkier fast twitch muscles. If you do too much long distance running, your slow twitch muscle fibers will take over and make you slower and nonexplosive.
I was once asking a client about running exercises they were doing in school athletics to improve running speed......the answer was disappointing and typical....
Some of the running drills were 1. mile runs 2. stadium steps for endurance 3. gasers for conditioning
"Did you run any sprints?" "No." Guess what? Those athletes aren't getting any faster....they are just basically running for conditioning.
Conditioning has its place.....but if you want to get faster, you have to train fast.....that means sprinting drills with enough recovery time to run each sprint full speed. About 1 minute of recovery time is needed for each 10 yards sprinted (50 yard sprints need about 5 minutes recovery time).
Running sprints after practice won't get the job done either....players are too tired at this point to give maximum effort. So, coaches, do your sprinting drills at the beginning of practice when your players are fresh.