A little over 3 hours a day, 6 days a week, for total practice time. I"m sure they can fudge in the running and sprints, or at least some.
Maybe that's why international players who don't go to US colleges seem to make it in the pros much more often than US college graduates.
I doubt they actually practice much more than 4 hours a day, as the body needs time to recover sometime. Talking 6 days a week schedules.