Maybe not combat sports... Not sure if you mean contact.

I played football and hockey. And started young. Real young at kindergarten with football. Then hockey around middle school.

Confidence... Def give some confidence and a taste for the "thrill of combat". Thinking back football in kindergarten was absolutely terrifying, but my dad required it. It spanned multiple grades, everyone was bigger, faster, and hit harder than me. It taught me real early you can be terrified and have a relentless pursuit of the objective. Eventually those bigger kids were trying to avoid, dodge, or get knocked down. Instead of just running my ass over. Hockey only translated to even more fun. There is no whistles or hut in hockey. You go until there's a goal, penalty, or buzzer while you clobber eachother over a disc or frozen rubber. Which hurts btw even in full gear.

As for the health...I will first say. That my body is perfectly healthy. Something that you don't hear a lot about, is what sports can do to your head. Reaching my 30s I began to show signs of epilepsy. Treatable but still fucked. This was a direct result of playing contact sports. I have taken more shots to the head that I can count. And I always wore head protection. Even a caged masked instead of a plastic visor. I never have taken a direct hit without head protection. I have several micro hemorrhages in my brain, very tiny and slight. I also have one big one that's the cause. Protect your head fellas, def dont lean into it with ur head.