So I was biking home yesterday, and my achilles tendon started hurting more and more, to the point where I barely made it home. So I had to drive today.

But, I figure that I should be back into it by Monday. And just think, I went from ~5-6 miles/day to 19 mpd...for a fattie, that's a big change.

Ice

are you angling your foot down during your pedal stroke?

Don't mess with your achilles tendon. If you significantly damage it, it can take a LONG time to heal. I would definitely go to a sports/ortho doctor and get it checked out, before I did any more major riding, running, or hiking.

It should feel better if you ice it and leave it alone for the weekend, but I would go see a doctor no matter how it felt on Monday. Even if it feels better by Monday, they will give you some exercises to help you prevent a future injury.

Good luck.

Yeah, and I need to stop doing that. I iced it, and this afternoon it's feeling a LOT better. Perhaps I'll switch off - drive in the morning, bike in the evening and vice versa.

Also maybe get a little more of your foot on the pedal so you don't have so much of a cantilever effect on your pedal stroke.