It depends on several factors. To begin with, do not do any activity that will raise your heart rate and blood pressure post-op for the three days that follow your procedure. Especially sexual activity including masterbation. Generally speaking, after three days, your implanted grafts are well seated and will not pop out from casual or even mild cardiovascular activity.
Can you hit the weights hard after three days? NO. But you can do light to medium weight reps as long as your head is elevated above your heart. No bench pressing either for at least one week, and then medium weight.
Let me say this, you don't want to pursue a routine of lifting heavy weight fewer reps to build bulk and mass. Think more in erms of toning through your routines. After one month, do whatever.
One last comment. Stay away from sit-ups, pull ups, ANY activity weights or not that puts stress or tension on your neck and/or sutures if you have strip. You don't want to stretch your linear scar because it takes much longer for the inner dermis layer to heal because it is soft tissue. There is no air circulating inside the scalp like the outer layer, the epidermis. The outer layer of scalp heals much quicker so it's kind of deceiving thinking everything is safe. Not yet. That's why I recommend waiting one month before you hit it hard.
I am basing this all on the presumption that you are a normal healer without complications and do not have any other medical condition that would affect your healing. Hope this makes some sense.