The Wedding - S1-E12
Plot hole: After Claudia's call, they decided that Lilly will meet her at the bar and the guys will meet Stuart. They're all at the apartment at the same time and the dudes have gotten to Stuart's apartment, convinced him to still marry Claudia and then go back to the bar right after Lilly gets there. And also giving a lot of time to Barney hitting on Claudia. There's no way that could happen in this order, they live right above the bar, Lilly was supposed to be there before Claudia.
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 ★