Yeah, and they're:
a) Paid very well for that (including overtime pay for working more than 8 hours in a day, where applicable)
b) Typically still only working 40 hour workweeks, if that. (For instance, a doctor could do a 12 hour shift, but then only do a few 6 hour shifts after, for a 30 hour workweek.)
c) Not 'hard physical labour', generally speaking. (Exceptions to this rule are typically great examples of a and b.)