The human body is amazing and can adapt to any conditions:

People climb Mount Everest with the aid of oxygen.
People can scuba dive to cold and dark depths of 150 metres plus.
People trek to the north and south poles for fun.
People can ski or board in the snow for up to 10 hours a day.
People swim for up to an hour in the Antarctic ocean which is the coldest in the world wearing no wet suit (just their heads covered).
45-50 minutes jogging, boxing, skipping and circuit training in your local park is a doddle compared to the above!