Factual error: Day 22 and day 67 are both on Sundays, which does not add up.
Factual error: When Ted is having a flashback about the first road trip in the Fiero, which would have happened around 1997or 1998, they are passed by a 2002 GMC Sierra. (00:06:10)
Answer: After running the marathon for Marshall with no training, he's allowed to ride the subway for free. While sat on the train, the muscles in his legs start to seize up after the marathon to the point it is painful to move his legs. This is why he can't move them. It's the same reason your body aches after a good session at the gym the day before.
Ssiscool ★