This! I'm fairly new to the hobby and after each league night I came home sore as all hell. Then I realized I was putting all my weight on my arms cuz I was leaning. It's hard to get used to as I think we have a natural tendency to lean when playing. Now I try to remain conscious to not lean when I play.
Quoted from EvanDickson:I don't know if there's a correct finger to use, but I've caught myself leaning on my machines with all my weight resting on my hands, which leads to sore arms and hands. Keep it light.