During a firmer than normal three-point touchdown in the tail wheel-equipped airplane, the pilot's feet slid down low on the rudder pedals, where they inadvertently came in contact with the floor-mounted heel brakes. Therefore, as the pilot made directional control inputs to the rudder pedals, he also made unintended brake applications. Those brake applications resulted in the airplane rolling up onto its nose, and then falling off to one side. When it fell off to one side, the end of the wing came in contact with the runway, resulting in damage to its interior primary structure. The pilot said there was no malfunction of the rudder or braking systems.