To be staffed

Exercises that require total body involvement improve and maintain fitness most effectively ? for example, jogging, running, swimming, cycling, and fast walking. Organized games and sports that have long rest periods within the play design have only a little influence on fitness. Programs especially planned to help individuals become fit are offered in different places: schools and gyms, private clubs and studios, and special, professionally organized clinics that pay attention to people with problems related to the heart or lungs. The individual must be careful in choosing an exercise program and should make sure it is staffed by experts in physical education or medicine.

What does "staff" mean here? I can only found this definition of the word staff (v.):

to be or provide the people who work for an organization:

Many charity shops in Britain are staffed by/with volunteers.

But here, the pronoun "it" refers to an exercise program. How can it be staffed? And what is the meaning?

Thanks.