Last blog we looked at the Borg scale of perceived exertion, today we’ll look at another method of finding effective exercise levels, maximum heart rate. The more physical exertion you do, the greater the demand from the body for oxygen. We use oxygen to create energy, so the more energy we need the more O2 demand, so your heart speeds up passing more blood through the lungs where it is oxygenated.
There is a limit to how high this heart rate can go, with variations according to genetics, fitness levels and age. The older we get the lower our maximum heart rate will be. Closely connected with this is resting heart rate, or the amount of times your heart beats at rest. The average for this is 72 beats per minute, with females being slightly faster. Again, there are variations according to fitness levels, genes and age. The fitter your cardiovascular system is, the more efficient your heart and lungs are at pumping and oxygenating blood, so the lower your resting heart rate will be. The author is proud to let you know that at the last test his was 42 – to be expected really for such an uber-fit personal trainer!
The important thing is that if we know a person’s maximum heart rate, we can then prescribe exercise levels at a percentage of this. For example, to maintain cardiovascular fitness, you should exercise at or above 60% of maximum heart rate for 20 minutes three times a week. To develop aerobic fitness you should exercise at higher levels, 65 to 85% of MHR (maximum heart rate). This is why some people and some aerobic gym machines have heart rate monitors, so you can see if you are exercising at the right level.
The most common formula for working out this maximum heart rate is 220 minus age. However this is only a guide, as maximum heart rates can vary a lot according to the factors mentioned above. If you have smart personal trainer in London then the better formula is
HRmax = 205.8 − (0.685 × age)
although there is still a deviation of +/- 6.4 beats per minute. The Borg scale is still very useful for seeing if you are going at the right level, as is the simple conversation test. If you can speak freely during exercise in full sentences then you need to speed up. If you can only get out single words between huffs and puffs then you may need to ease up a bit. Ideally you should only be able to speak in short brief sentences before having to get some air. This equates roughly to 60% of maximum heart rate. Remember if in any doubt have a word with your GP before starting or increasing exercise.