Swim it, run it, get out of breathe and sweat a little - what do you do?

Just finished a hard 2 mile swim.  I have always swam, well most of my life anyway.  I have done a lot of other sports and activities but swimming has been a constant for the last 35 years.  There is nothing quite like the apres-swim feeling, as the ‘thank you’ chemicals begin to circulate.  They seem so happy that every tendon, ligament, joint, bone and muscle has been moved, stretched, pulled, compressed and flexed.  They seem to race around the body with purpose and a smile.  They announce the gratitude of physical excitation.

What sport or activity gives you that boost, that invigoration, the warm fuzzy feeling of satisfaction?