Why is exercise bad after FUE?

It is best to ask your surgeon about post operative care as each doctor has their unique regimen.  Most doctors don't want you to harm the graft due to exercise. It is more about using common sense.  Some doctors may tell you light exercise is ok.

The reason why we limit heavy exercise immediately after a Hair Transplant is to reduce the possibility of dislodging grafts by excessive sweating or elevated blood pressure.

Blood circulating to the grafts is good, but increased blood pressure and straining that comes with exercise can dislodge them early on in the healing process.

Yes you are right , blood  is good for implanted grafts . But  you should be carefull about do not make very hard exercise to increase blood pressure so much that may cause pop up of the implanted grafts and do not hit your head to any where.

After 4 days, you can do whatever you want except for scuba diving. Full exercises is just fine even running a marathon if you want to

After hair transplant we ask patients to avoid exercise for 7-10 days because once you exercise, the blood supplies goes to your muscles. We want to enough blood supply to remain in the scalp, so these grafts can survive.