A concern would not be a hit but a fall. Some of the worst hockey concussions were from falls and head impacts on the ice.

I play ping pong at the gym/Y. I played 5 games to 21 today and broke a decent sweat. I also use a rower for a more serious cardio workout. I row against the clock on the rower. There are plenty of exercise machines with electronic based challenges or even networking to others on their machines.

I have not played a contact sport in 45 years due to concern of a head hit. BUT, I have still had 10 considerable head hits from normal life. They are enough of a risk.