Is it better to run outside or on a treadmill?

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Tags

1. #reasons
2. #easier
3. #doesn
4. #runners
5. #turnover
6. #assists
7. #running
8. #outdoors
9. #however
10. #variety
11. #faster
12. #their
13. #great
14. #reason
15. #making
16. #correlate
17. #training
18. #treadmill