It's easy enough for a person in very good shape to run 12 miles. Some marathon runners cover >100 miles per week in training (in their case, of course that is

It's easy enough for a person in very good shape to run 12 miles. Some marathon runners cover >100 miles per week in training (in their case, of course that is their main training activity). All together, though, those bragging points add up to something implausible.