Some doctors will limit your friend's physical activity until the pacemaker has settled into your chest and the lead wires have had a chance to heal inside your heart. There is a small risk of infection or pulling the leads out if following instructions aren't followed.
In most cases, having a pacemaker won't limit friend from doing sports and exercise, including strenuous activities. It may be wise to avoid full-contact sports, such as football. Such contact could damage your pacemaker or shake loose the wires in your heart. The doctor will tell your friend how much and what kinds of physical activity are safe for your friend.
Thanks for your question, and hope the answer provides the information you want. Take care. .