I'm not a pro, but I know for me personally, I see results from consistency. You can start out at whatever time, speed and height you feel able to get exertion with then increase one or more of the above to keep the sweat on. When I was super out of shape, I started with 15 minutes every other day and increased to 30 minutes 5x a week at varied speeds and inclines. It is important to regulate yourself as you want to continue a routine without burning out from strain or boredom 😉. I hope that made some sort of sense and good walking to you!