Sep 26, 2012 Lifting Weights The other day my son was lifting some dumbbells that we have in the house. He was trying to single hand curl 2lbs and max out on 5lbs. While I was watching him lift I realized that he was trying to lift 25% of his body weight with the 5lb dumbbell. This was his first time hitting the gym, so I can’t imagine what he would do on the second day. I was very impressed as he played with his new toy. Also, if I were to single hand curl 25% of my body that would mean I need a 40lb dumbbell. I guess I have a new goal, increase my curls from 15% to 25%.