Thank you for your question. In regard to how long a person can stay physically fit with HIV, this varies tremendously from person to person.
Some people can stay fit, and capable of playing physically demanding sports for years.
Other persons may quickly lose their physical fitness and competitive edge. How long a person remains physically fit depends on many variables including, how well they take care of themselves, severity of side effects from drugs they may be taking, the virulence of the strain of HIV that they have, etc. Just because a person has HIV, does not mean they cannot do well in sports. Magic Johnson is a great example of how an athlete can have HIV, and still do well in sports. Before he retired from basketball, he was doing well as an athlete, despite his HIV status.