In prepping for your long runs that will occur during the endurance build phase, we are going to run medium length runs with the following formula: run 9 minutes and walk 1 minute, run 9 minutes and walk 1 minute, and repeat until you complete the 3.5 miles. It is important to try to walk the 1 minute intervals instead of stopping. The 9 minute intervals should be at conversational pace. As you build your endurance, it should be easier to hold a conversation at a quicker pace.