Warm up by running a few laps up and down in the sand. When you're ready, mark off a distance by using two landmarks or by drawing a line in the sand. Sprint from one to the next—aim to have each sprint last 12-30 seconds, with a ten-second rest between each one. The resistance from the sand makes these so much harder than regular sprints so you'll feel them quickly. Tip: Running barefoot is a lot different than running with shoes on. Focus on not striking with your heel first.