Two years of cycling a lot.
Figuring out different ways to do cardio.
Trying running bit by bit, never going more than 5 or so miles.
Cycling 100km in one go, 4000+ miles overall.
Doing different ellipticals, from super nice LifeFitness gear to crap ellipticals that my dad got on Craigslist for like $30.
Hiking 15 miles to close my rings because I couldn't bike that day, and I didn't want to run or get injured.
But I did it.
I ran a new 10K after two years.