Yes, their taining regime is exceptional. We must keep in mind USMC is not small specialist force - but larger than some regular armies. I think three things mark them out. First their training regime is exceptional. Second every marine, cook, cleaner, general must be
proficient as a rifleman. This is something marine culture revovles around. Third, every marine must meet the demanding pysical training - even a 60 year old Marine general has to be able to complete a mile within alloted time. Which is why even senior Marine officers will always look lithe and lean. No excess tubby fat on them unlike our senior officers.
This is 60 year old Commandant of the Marine Corps, Gen. Joseph F. Dunford, Jr., doing his Combat Fitness Test which included shifting 60 lb ammunition trays.
Major General Vaughn Ary, Staff Judge Advocate to the Commandant displays lifting 30 lb ammo can 100 times during combat fitness test on December 4, 2011
https://en.wikipedia.org/wiki/Combat_Fitness_Test