sadly not. The force of gravity on the wrist weights as you punch is downward therefore all that happens is that the shoulders fatigue prematurely from stress unrelated to the mechanics of punching. They will not help you punch faster or harder in any way. If you want to experiment with a specific exercise that could help whilst mimicking the movement of punching, search for footage of a 'standing neider press'. At least when done properly, you work the body with the correct biomechanics. Personaly I prefer to keep resistance work, and striking practice as completely seperate entities.