Nothing beats getting out to into the great outdoors and going for a wall however this is not always possible, especially when you are a busy mum! Over the last couple of months I have been doing walking workouts on You Tube. Walking workouts a fantastic for beginners, they are simple (no complicated moves), you can do these workouts in the privacy of your own home, they cater to different abilities and they are FREE! I recommend starting from the one mile (1.6 "ish" km) and working your way up to the 2, 3, 4 and 5 mile workouts when you feel comfortable to do so.
