Just ran my 1st marathon at 53 year old! Before ChiRunning, I never ran more than 3 miles before pain stopped me. With ChiRunning app and book I found that running long distance does not have to hurt!!!! Running can be fun joyful experience that changes your life. I am a physician and I am convinced that with ChiRunning app and book, anyone can run marathon without pain or injury. This app costs $10. Couple of burgers costs more... As a physician, I highly recommend this app and ChiRunning program.