How can I find out how fit I am? I am a 44-year-old woman who tries to jog in the park three times a week.

There are a number of ways to assess how fit you are. Some can be complicated, however, so my suggestion is simple and easy to do in a park, whether you're a walker or a jogger.

I'd recommend the Cooper 12-minute walk/run test. The primary objective is to cover the greatest distance in 12 minutes. You fall in the 40-49 age category, and as a woman anything between 1.25 and 1.34 miles is classified as excellent; 1.12 to 1.24 is good; 0.99 to 1.11 is fair; and below 0.98 is poor. (In the same age group, a man would need to cover a further third of a mile in each classification.)

These classifications are standard terms, so if your results come out as fair or poor, do not be disheartened. Pay a little attention to how hard you run, and gradually increase the length of your runs, and you'll be surprised how quickly you can progress.

Fitness testing can be a great motivator and it provides a base line for progress. But a word of caution: such tests do encourage all-out effort, which also incurs a greater degree of risk. If you have any medical complications, check with your GP first, or do a less vigorous dummy run to give you an approximate idea of how you score.

If you're unsure about measuring a mile, do the test wearing a pedometer. Although this introduces a small element of error, if you always test in this way you will have a fairly reliable tracking system; 2,000 steps is approximately one mile. The greater the number of steps you take in 12 minutes, the better.

And remember, aerobic fitness is just one component of physical fitness. For a better impression of overall fitness, include muscular fitness and flexibility tests, which can be done at home or with a personal trainer.

· Joanna Hall is a fitness expert (joannahall.com). Send your exercise questions to: Guardian Weekend, 119 Farringdon Road, London EC1R 3ER
E-mail: weekend@theguardian.com