Hi All. I'll be starting week 5 tomorrow and I'm currently running with a group on Monday, Wednesday and Saturdays. Some days I cannot make it to the group runs so I run on my own with the app. When I run solo I run in the forest on natural trails, but when I run with the group we run on an asphalt track. Each time I run with the group I end up having pain my knees and calves and ankles, but when I run on my own it seems to be fine. Could the running surface make that much of a difference in the impact on my body? I like the social aspect of the group, but it's always much more difficult for me. Anyone have a similar experience?