On the Staff administration page you can hire support staff, groundskeepers, PR managers and doctors. Hiring or firing a staff member costs £ 1,000, and the weekly salary is £ 500.
You can also manage the work of your dietician there.

Club Doctors

Doctors take care of injured athletes and decrease their recovery time. The more doctors you have, the faster injured athletes heal. Their effect becomes visible daily after the athletes (injury and test) update.
Doctors don't prevent injuries, so you don't need them if all of your athletes are healthy. - see form and injuries

Dieticians

Sadly the Dieticians don't help me lose weight, but in Maxithlon they have the following impact:

The Dietician allows you to put up to 5 athletes on a customized diet in order to help them increase or decrease their weight. The effect of the diet becomes visible on Thursday after the training update. The weekly costs of the dietician depend the number of athletes he takes care of, and increase progressively.

The cost of dieticians is as follows:

Dietician's weekly costs:

1 athlete £1k

2 athletes £3k

3 athletes £6k

4 athletes £10k

5 athletes £15k

PR Managers

PR managers affect the relations with your sponsors and will therefore cause a gradual increase of the income from the club's sponsor and the individual sponsors, up to 10%. Their effects become visible on Monday after the financial update.

Groundsmen (Groundskeepers)

Groundskeepers are in charge of maintaining the arena. They increase the efficiency of your arena on a daily basis, and they are needed to deal with the efficiency losses which your arena will have without them. They also reduce the minimum efficiency your arena needs to avoid fines (see also 2.5 Arena, Efficiency).

Arena Efficiency

Your arena has to be kept in good repair. Its efficiency tends to decrease slowly on a daily basis. Additionally, when you host a meeting, the efficiency will drop by a certain amount, which depends on the ticket income from the meeting. In order to avoid paying fines for having too low efficiency, the efficiency should never get lower than 80-85%. To recover the arena's efficiency you should hire groundskeepers. The bigger the arena is, the more groundskeepers you need to get the same recovery rate. You can also use the "Condition recovery" button to repair immediately to 100% efficiency. But using this button is in most cases more expensive than employing groundskeepers.