No don't shadow box with 5 lbs you do 3 lbs anything above 3 lbs will damage your joints and you'll feel it in the future. Body weight exercises, medicine balls and intense heavy bag work increases power.

Shadow box with 5 pound weights in your hands or gain weight and the power behind your punches will increase with your weight increase.

I could never understand why men want to punch each other's heads until their brains are scrambled.

Light wieghts and form.