I use a 3 pound hammer at the moment. Thinking of upgrading to 2000 g.
The trick is to hold the hammer close to the head so you don't have to use a lot of underarm torque to lift it up.
It is a lot less tiring, and a lot less damaging to the elbow.
With short handles, you use less torque on the underarm, and you can keep hammering for a lot longer because you use the bigger muscles.