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Monitoring Aerobic Exercise Intensity

By August 6, 2009 October 20th, 2011 No Comments

Whether you are a personal trainer, have one or are simply looking to get fitter then monitoring exercise intensity is necessary both to keep the session safe and also to make it effective. Methods are

  • Heart Rate
  • Perceived Exertion
  • subjective methods
  • exercise pace

Heart rate is the most common and traditionally thought of as the most accurate method of measuring heart rate, however there are some misconceptions with the heart rate method. The main methods for determining heart rate manually is to measure the pulse at the wrist or the neck or to use a heart rate monitor. The latter is preferred as many inaccuracies can arise taking your own or someone else’s heart rate, especially if the heart rate being taken is really high!

Many people know the traditional method for working out the maximum heart rate, which is 220 minus age. So for a 38 year old the theoretical maximum heart rate would be would be 220 beats per minute minus 38 giving us 182.  Maximum heart rate is important to know as we can then work out percentages of this maximum for particular types of training. However what most people don’t know is that this calculation has an error variable of +/- 11 BPM (beats per minute). Personal trainers (or individuals) should be aware of this, and only use this calculation as a guide. The only way to truly gauge maximum heart rate is to train to exhaustion and measure the heart rate, although this can only be done with some people, and it’s obviously not a barrel of laughs! As a guide 60-90% of MHR will be the right level to make someone get fitter, although if you are really unfit then 50% might do it.

A major myth associated with heart rate and aerobic training zones is that a training heart rate within the O2 energy system (so up to 60% of MHR) will burn the most fat. No such relationship between an individual’s heart rate and their metabolism of fat while exercising exists. Some people have been recorded in scientific tests as metabolising fat up to 97% of maximum heart rate, while others stopped metabolising it at just 54%. The point here is that individuals respond differently to exercise, and any attempt to provide standard calculations or zones is problematic. So ignore those pretty graphs on the machines in the gym!

Rating of Percieved Exertion (RPE)

This scale was invented by a Scandinavian scientist called Gunnar Borg (it is also sometimes known as the Borg scale) and is a scale of how hard someone feels they are working during exercise. The response of the person exercising should also be taken into account-the symptoms of exertion should be noted, such as breathing, muscular fatigue and the subjective feeling of effort. The classic Borg scale below rates effort between 6 and 20:

rpe

Subjective Methods:These are the least accurate of the heart rate and workload assessment methods, but in the field they can be very useful. The talk test is a good indicator that a personal training client is working at 60% of MHR or above; if they can speak in whole sentences then the pace is too slow. If they can only speak in short broken sentences then the pace is most likely around 60% of MHR. If they can only give one word answeres than we are looking at 75-90% MHR, if they cannot speak at all then the level is pretty darn high.

Training or exercise Pace: Formulating workouts based on specific exercise speeds can be a very accurate and useful method. A timed run over a set distance measured over a period of training weeks or months is a good basis of testing fitness improvements, some others could be the bleep test, rowing intervals at a certain pace, and so on. Many of these formulaic workouts are easier on gym equiptment, as they give accurate readings, although doing many of our personal training sessions outdoors at Diets Don’t Work there are also lots of other options.

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