Being an ex smoker, sedentary working from home, overweight, no exercise and relatively old etc, I was worried that if I attempted to run, either my heart or knees would pop out. Although I have been out of breath with aching muscles - nothing bad has happened and I'm even finding it fun, which is a surprise.
The reason for my post is to encourage anyone contemplating this program that it's worth a go, can be fun and that their message is to run it at your own rate, so very slow is fine. Also, my thanks to those involved with this app and to everyone who posts which all helps with motivation.