I train in two ways outdoor and indoor. I run my long miles outdoors. I learned a route and run it for memory. I also use audio GPS updates. However, things happen. Sometimes the route is a problem. For example, there may be new signs on the sidewalk, or bags of garbage. I usually run indoors on the treadmill. I run indoors four or five times a week. It helps me run on hills, but it can be boring. I prefer being outdoors.