Originally Posted by Donald Lee
I think leaning forward makes it harder on the triceps due to your center of mass going further from the fulcrum of your elbow, thus, increasing the lever arm. I'm kind of tired right now, so I could have just pulled that one of my ass.
I think leaning forward also allows you to recruit your upper chest muscles as well and recruits a little less anterior delts due to increased recruitment of upper chest and smaller angle of shoulder extension.
I know Borge Fagerli has written about a contraption he made to weight dips from your upper body as opposed to your hips to allow more forward lean and chest recruitment.
Leaning forward makes it harder on everything...