man strength
Strength a man is bestowed with in his mid 30's that isn't physically apparent to an outside observer. A man needs to do nothing to recieve it other than grow old. Many unsuspecting sons and young males looking to prove them selves "manly" aren't aware of this phenomenon and underestimate the middle aged man.
John, the better athelete, can't win a game of one on one because his Dad has man strength.