I'm currently in my first year of med school. I didn't run for my school's team when I was in undergrad, but I'll try to offer some advice and perspective.
Don't feel like you have to major in something extremely difficult or even something in the sciences. You have to complete your prereqs, and I'd also advise taking a few upper-level bio courses beyond the minimum requirements, but you can do this while majoring in anything you want. It's way better to be an English or economics major with a 3.8 GPA than a biochem major with a 3.5 GPA. Med school admissions is a numbers-driven process, and they don't give as much credit as you might expect for completing a tough major. If you want to major in something challenging and you can handle it along with athletics, go for it, but don't feel like you have to.
If you run collegiate track, you might just want to go in with the plan of taking a gap year between college and med school. Volunteering, research, shadowing, and MCAT prep will be difficult to balance with athletics and school. If you need to put some of that off until after you finish, you should. The last thing you want to to is to sacrifice your GPA or do worse than you should on the MCAT because you were trying to juggle too many things. It's a long journey, and taking a little bit of extra time to put together the best application possible will not be a mistake.
Use your summers wisely. If you can knock some coursework out over the summer, that will really help to lighten your in-season load. Especially good if you can get some of the more time consuming lab courses out of the way. Summer is also a good time to do some research.
All in all, I think running in college and getting into med school will be tough but doable if you're reasonably smart and you have good time management. I'd expect your social life to take a hit, but I don't think you'll be completely unable to go out ever. You'll also have to be pretty disciplined about studying on road trips, which can be difficult if your teammates are hanging out and relaxing. But I think it will be doable if it's what you really want.