I was discussing this topic with a client yesterday who took up the challenge to run 100 miles in 12 days. He is an ultra-marathon runner so already has a great level of endurance and fitness to complete this challenge. When training your muscles in any way, you create micro-trauma in the muscles which usually requires 24 hours recovery time to repair and restore. This is why it is advisable to not run on consequetive days. If you run or train too many days in a row, you are eliminating the recovery phase and repeatedly causing microtrauma and fatigue to the soft tissues and muscles. This is where how you break up your training to allow these important rest phases. E.g. in the gym, we exercise lower body on one day and the upper body on day two so that the muscles are trained and able to recover every other day. When it comes to running, training volume can be managed to help avoid injury. The client has to run 100 miles in 12 days. He could therefore run 8.33 miles per day. However t