Listen to Your Heart – Knowing What is Intensity!

Intensity refers to how strenuous you engage in a particular physical activity or exercise. In theory, our heart rate is directly related to exercise intensity, and there are valid and reliable formulas available for measuring our desirable range of heart rate for exercises. You may also need a monitoring device (e.g. heart-rate monitoring watch) to measure your exercise heart rate more accurately. Alternatively, you may use "talk test" which is rather a simple but subjective approach to determine your personal exercise intensity.

Method	Intensity		Considerations
Method	Moderate	Vigorous	Considerations
Talk test	Breathe somewhat harder and faster than usual Being able to talk in short sentences	Breathe much heavier than normal Unable to talk with ease	Simple and easy to do
Age-predicted maximal heart rate	65-75%	> 75%	Easy to apply, but less accurate for younger adults and highly fit persons
Heart rate reserve	40-60%	> 60%	More personalised and accurate, but involve more calculation

Age-predicted Maximal Heart Rate Formula

Target heart rate zone = (220 – age) × Intensity %

Example: A 40-year-old man is doing running practice, and the range of his heart rate upon moderate intensity is calculated as follows:

Target heart rate zone, lower limit = (220 - 40) × 65%
= 117 beats/minute
Target heart rate zone, upper limit = (220 - 40) × 75%
= 135 beats/minute

Therefore, if the man wants to practise running with moderate intensity, his heart rate should maintain a level of 117 to 135 beats per minute. If the heart rate exceeds the upper limit of 135, he should lower his running speed.

Heart Rate Reserve (HRR) Formula

HRR = [(220 – age – resting heart rate) x intensity %] + resting heart rate

Note: Resting heart rate should be measured after the person has sat or lain down for 5-10 minutes.

Example: If the man in the above example has resting heart rate of 60 beat per minute, the heart rate range of his moderate intensity exercise is estimated below:

Lower range, HRR = (220 – 40 – 60) x 40% + 60
= 108 beats/minute
Upper range, HRR = (220 – 40 – 60) x 60% + 60
= 132 beats/minute

Since HRR method considers both age and resting heart rate into calculation, the results can be more personalised for exercise training.