Knowing how to gauge your exercise intensity can come in handy when you want to set or revise your fitness goals.

For instance, people who want to ditch their sedentary lifestyles may not want to instantly go into high gear, while others who have been exercising regularly may want to ramp up their fitness routines to get their hearts pumping harder.

The most precise way to determine exercise intensity is to measure one's oxygen consumption. But this is a laboratory-based test and is unsuitable for daily assessments, said Dr Ho Boon Hor of Changi Sports Medicine Centre at Changi General Hospital.

Are there other ways to tell if you are doing light, moderate or high intensity exercise? Dr Ho offers some guidelines.

Gauge by how you feel

Exercise intensity is a subjective measure. What feels to you like a hard run can feel like a breeze to another person. Look for the following signs to help you gauge how intense a particular workout feels.

MODERATE INTENSITY

•An increased breathing rate. However, you are not out of breath.

•Light sweating after about 10 minutes of exercise.

•You can talk in sentences, but you cannot sing.

HIGH INTENSITY

•Deep and fast breathing.

•Profuse sweating after a few minutes of activity.

•You can speak only a few words at a time in one breath.

Gauge by your heart rate

To use this method, you must first figure out your maximum heart rate, which is the upper limit of what your cardiovascular system can handle during physical activity.

The basic way is to subtract your age from 220. For instance, if you are 45, the maximum number of times your heart should beat per minute while exercising is 175.

If your heart rate is at 50 per cent to 70 per cent of your maximum rate, the exercise you are doing is of moderate intensity. High intensity exercise will cause your heart to pump at 70 per cent to 85 per cent of the maximum rate.

Those who do not use a heart rate monitor can check their heart rate manually by following these steps:

•During exercise, stop momentarily and take your pulse for 10 seconds.

•Do this by placing your index and third fingers over the carotid artery of the neck, beside your windpipe. Or, place two fingers between the bone and tendon over your radial artery at the wrist, which is at the thumb side of your wrist.

•Count the number of pulses in the 10-second frame. Multiply it by six to get your heart rate.

Those who have been exercising regularly can safely scale up their routine by doing the same type of exercise, but at a higher intensity, using the above tips as a guide, said Dr Ho.

If you are breathless, in pain or unable to work out for as long as you normally do, your exercise intensity is probably higher than what your fitness level allows, he said, adding: "Return to your previous intensity level and build the intensity more gradually."

Poon Chian Hui