In this case, over time works better than overtime. He even says over time in the beginning. Overtime means something else.
How Your Fitness Develops Over Time (Cycling Tips For Beginners)
More EDITOR@WORK blog entries
Blog entries by Tom Gillispie
Entries from The Dog Blog
Blog entries from The Auto Racing Journal
(a book of great stories about the Intimidator)
(the book of great NASCAR stories)