So, although toenails trimming and painting is safe for marathon runners, you should definitely not let the pedicurist remove your thickened, callused skin with a razor or emery board. The callused skin serves as blister protection for your feet, so if it's removed, you'll be more at risk for blisters. Instead of removing your calluses, ask the pedicurist to spend some extra time massaging your feet and calves. It will feel great!
Also see: Runners' Foot Problems