If you've got injuries below the knee, then you might want to check out:
web site and click on the "foot drills" link and read an article by Russ Ebbets, DC regarding 6 simple exercises to do. He says these drills will aid with shin splints, plantar fasciitis, Achilles tendinitis, knee problems and will increase your speed.
He's done some research to back up his claims and is affiliated with USATF. Seems to be a very simple solution for problems most Masters T & F competitors suffer.