Newton's 3rd law of motionsays that if an object exerts a force on another object, then an equal and opposite force is exerted by the second object on the first. So, when a boxer punches the face of his opponent, it is just as likely to break his knuckles as he is to break the other person's jaw. The gloves absorb some of the impact and protect from injury. They increase the time over which the momentum change takes place, hence reducing the impact.