You didn’t say how long ago you had THR, your age, weight, work you do, or what Grit class is. If it involved hopping, or your surgery was recent, you may have done a very bad thing. I felt absolutely fine for two years, then overdid it, and had a permanent setback, where I had to give up running entirely. There are dozens of readers of this website who ran marathons and ultra’s after THR, but it is a self-selected group. People who had to give up running probably won’t contribute here. Send me an email if you like: firstname.lastname@example.org. Best.