Intensity relates to the level of effort required by a person to do an activity. Your heart rate can be used as a measuring tool to indicate the “challenge to the cardiovascular system that the exercise represents”. But how do you know if you are working at an intense level?
There are a number of methods we use to determine our intensity during exercise – heart rate monitors, the talk test (which measures breathe frequency from carrying a normal conversation to not being able to speak), PRE (Perceived Exertion Scale) and the 40 year old formula of 220 minus your age!
Perceived Exertion Scale
The PRE scale, which was developed by Borg (see graph below), is a way of interpreting how hard you feel your body working. Signs such as, our heart rate increasing, our breathing becomes more rapid or shallow, we sweat more and we start to feel fatigued. While this method is up to our own interpretation, it does seem to provide a good estimate of how hard we are working and we are able to adjust our intensity. There are variations of this scale (1-10) and (6-20) but are fundamentally based on the same principles.
The age-old formula which is quite simple to use and popular not only during physical activity but also used by doctors to diagnose heart conditions, is now being called ‘flawed’ by scientists. The popular measurement to calculate maximum heart rate of “220 minus your age” is flawed, as they found significant differences between men and women despite the formula used for both. Not a study that can be ignored, given that more than 25,000 stress tests were analysed to find this calculation is out of date. (Note: the sample was men and women between 40 and 89 years of age).
Although everybody’s peak heart rate declines, as you get older, it is more gradual in women. So what the research is telling us all this time “the formula overestimates the peak heart rate younger women can achieve and underestimates the peak heart rate of older women’.
Therefore they have adjusted the new calculation to:
Women: in the range of 40 to 89 years as 200 minus 67% of their age;
Men: the formula is 216 minus 93% of their age
Some other interesting facts the study found:
- Younger men have a lower resting heart rate and higher peak heart rate compared to that of women;
- Researchers suggest hormones and testosterone could be strong reasons behind the differences;
- A re-evaluation was needed given the changes in average body weight, fitness levels and attitudes towards exercise since the 1970’s ;
- For women younger than 40 reliable results were not found, given the studies analysed women in the older age category
Well, it doesn’t seem there is one scientifically proven way to measure your intensity but one thing I do know is that I have a different heart to you, so perhaps there is validity in getting to know what works for you. Develop your own ‘signs’ and use that to compare the next time you get out there and workout.