What if I want to walk outside?

That’s just fine and very much the equivalent of walking on the treadmill. For optimum results, try and find a nice flat walking area where you will be able to maintain a steady pace. For instance, if you know you’ll have to cross a lot of streets, go around the corner and come back when you have the right of way, or walk in place while you are waiting for the light to change. Going with the flow can provide opportunity to see new and interesting things too!