noun
running
RUN-ing/ˈrʌnɪŋ/
The activity or sport of moving quickly on foot.
She enjoys running along the river each morning.

Etymology
Run combined with the activity-forming -ing names the action itself. The noun already referred to rapid motion on foot in Old English, so the sporting sense preserves its central physical meaning.
In context
I think running has helped keep my body from becoming like a lot of 80 year-olds and has kept me healthy. I think running has strengthened my body so that I've healed more quickly.