A heart rate monitor can help to ensure that you don't work too hard - or take it too easy! - in training sessions. Depending on the session, your target heart rate will be anywhere between 60 and 95% of your maximum.

To know your target heart rate though, you'll need to know your maximum. If you're very overweight or a complete beginner, it's best to use the very approximate formula of 214-(0.8 x age) for men and 209-(0.9 x age) for women to estimate your maximum.

Unfortunately for 5-10 per cent of the population this figure can be wrong by up to 24 beats per minute. It's much better to find your maximum through running. Do this by warming up, then running as fast as you can evenly for three minutes (ideally on a treadmill), then resting with two or three minutes gentle running, then repeating your three minute maximal run. During your second run you should get a higher maximum heart rate than with any other method - though use your heart rate monitor to take readings throughout it, as your heart rate may peak before the end.

There are three broad training zones:

• 60-75% - easy
• 75-85% - moderate
• 85-95% - hard

But… don't fall foul to a common misconception: these aren't percentages of your overall maximum heart rate - they're percentages based on your working heart rate. It makes a big practical difference to a regular runner. It's easy to do, but it takes more explanation than most gyms want to deal with.

1. Find your maximum heart rate (see above) eg 206
2. Find your resting heart rate (laying still, soon after you wake up. Ideally take an average over a few days). eg 56
3. Subtract the resting rate from the maximum. This figure is your working heart rate. eg 206-56=150
4. Take whatever percentage of your working heart rate that you're aiming for (eg 60% for an easy run eg 150x0.60=90), and add it to your resting heart rate eg 90+56=146. The final figure is your personal target heart rate.

• 60% Recovery run - dead slow. It may feel biomechanically odd at first, but it's important. 30-40 minutes.
• 60-70% Long, slow runs - up to 65% the body is teaching itself to burn fat as fuel (useful for marathons). Anything from 1-3hrs.
• 70-85% Fartlek - speedplay (moderate-paced runs with random fast bursts). 30-60 minutes.
• 70-85% Undulating route - peak at 85% on the climbs. 30-90 minutes.
• 85% Anaerobic threshold run (or 'tempo run') - this teaches your body to run hard for long periods. Approximately 10-mile to half-marathon race pace. Sample session: 1.5 miles at 60%, then 15-20 mins at exactly 85%, then 1.5 miles at 60%.
• 85-90% Approx 5K-10K pace. Sample sessions: 6 x 800m peaking at 90% in each rep; 5 x 2000m peaking at 85% in each rep.
• 95% Peak heart rate at 400m rep pace (not full-out race pace). Sample session: 12 x 400m with 200m jog recoveries, making sure recovery heart rate drops to at least 70%.

NB: you can't usefully use a heart rate monitor to pace intervals below 1000m - rather, the figures above 85% are a guide to what you can expect to reach at the end of each repetition.

1. You may not be using an accurate maximum heart rate (if you've estimated it). Add 12 beats your theoretical maximum and try the calculations again.
   or...
2. You may be using percentages of your maximum heart rate rather than your working heart rate (see above).