Traditionally, we use the formula of 220 minus age to ‘guestimate’ your max. For example, if you are 40, your estimated MHR would be 180 (ie 220-40). You can then calculate training heart rates from this, using a formula such as 70 per cent MHR (which would be 126).
Its quite simple, but unfortunately its not accurate for everyone. American sports scientists have modified the basic formula to allow for gender: 214-(0.8 x age) for men, and 209-(0.9 x age) for women.
If you want to find your true MHR, youll have to do a little work and some measurement with your heart rate monitor.
Sports science laboratories often use a graded treadmill run to establish MHR. The speed of the track is gradually increased until you can no longer keep up, and your heart rate at this point is assumed to be your MHR.
However, a combination of short runs will give you higher readings still, and this would seem to be your best option. Run as fast as you can evenly for three minutes (ideally on a treadmill), rest with two or three minutes gentle running, and then repeat your three-minute maximal run. During the second run you should get a higher MHR value than with any other method, though use your monitor to take readings throughout it, as your heart rate may peak before the end Shorter, faster bursts dont appear to work, as the leg muscles then become exhausted before the cardio-respiratory system.
Recording your MHR
Make sure you’re healthy and well clear of injury and infection.
Ensure that your transmitter belt is attached securely and dampen the electrodes.
Warm up thoroughly for the task.
If your heart rate monitor records data, set the recording interval to five seconds and view the data after your test.
Otherwise, view the receiver every 10 seconds in the last minute of your effort, as the max may not be at the very end.
Factors affecting your MHR
Both the duration and intensity of your warm-up will affect your heart rates in your test. A longer warm-up of moderate intensity will give higher readings than a quick, light jog, because your body temperature and muscle blood flow will be greater.
You need to be fresh to be able to perform at your true max. If you have trained hard on the previous couple of days, you are unlikely to be able to run at sufficient intensity to register your genuine MHR.
Rather than one continuous run to exhaustion, or a graded test, try a couple of hard three-minute bursts after a thorough warm-up.
Research has shown that you are likely to get slightly higher readings if you run on a treadmill rather than outside. A treadmill can also help you keep level pace in your three-minute bursts, and may help to prevent you setting off way too fast and fatiguing early.
Mode of exercise
Its important that you use the mode of activity that youre training for. For example, your MHR from a cycle test is almost certain to be lower than your running MHR, unless youre also a highly trained cyclist.
– excerpted from Runners’ World
The key is to put a load on your heart, and the key to that is obviously to START!.