MANY FITNESS WEARABLES LIKE FITNESS BANDS AND SPORTS WATCHES COME WITH HEART RATE MONITORS. HOW DOES A HEART RATE MONITOR HELP ME IN MY EXERCISE?
Heart rate is a measure of how fast or slow your heart beats per minute. Normal heart rate is between 60 and 90 beats per minute. During exercise, heart rate will increase according to intensity and oxygen consumption. If you exercise regularly, there is an adaptation in our body, including heart rate.
You can monitor heart rate, not just during exercise but also at rest, to see the effect of exercise on your body. Here are ways to use heart rate in exercise:
RESTING HEART RATE
Resting heart rate (RHR) is the lowest and slowest heart rate at rest. Normally, the best time is to check your RHR is before you get out of bed. The lowest resting heart rate is associated with age. The older the person is, the higher his or her RHR is.
When you exercise regularly, your RHR reduces. This indicates that your fitness has increased. It is good to keep a log of your resting heart rate every morning. It will also help you to determine recovery from previous day’s workout.
If your RHR is higher than usual (may be 5bpm higher, after a workout), it indicates that you have not fully recovered.
EXERCISE INTENSITY
Heart rate increases during exercise, according to intensity. The higher the intensity, the higher the heart rate.
There are two ways to know the intensity of exercise using heart rate. One is the percentage of maximum heart rate and the other, the percentage of heart rate reserve.
One must know his maximum heart rate (usually estimate), resting heart rate and target heart rate zone. The heart rate zone according to intensity of exercise is as follows:
Percentage of maximum heart rate (MaxHR):
Low intensity:
Moderate intensity: 64-76 per cent
Vigorous intensity: >76 per cent
Percentage of heart rate reserve (HRR):
Low intensity:
Moderate intensity: 40-60 per cent
Vigorous intensity: >60 per cent
This method will keep you exercising at the intensity that you require. In some cases, it may help you to exercise at a safe intensity, like low and moderate intensity, in case you are worried to exercise at vigorous intensity or are not sure of your health status.
TRAINING TO IMPROVE PERFORMANCE
Training zone: You can use heart rate to determine your training zone. Aerobic training zone is normally between 50 and 90 per cent of your maximum heart rate. If you want to do a lactate threshold training, exercise at >90 per cent of your maximum heart rate.
Training adaptation: Your body will adapt according to your training, so will your heart rate. Your heart rate will be lower at the same effort or speed after training. You can monitor the effects of training on your heart rate by logging it to monitor your progress.
RECOVERY HEART RATE
Recovery heart rate is the difference of heart rate that is taken immediately after stopping exercise and one or two minutes after stopping exercise.
Normally, the difference is >12bpm after one minute of exercise or >22bpm after two minutes of stopping exercise. If the difference is less than 12bpm and 22 bpm after one minutes and two minutes of exercise respectively, it shows a slow response of the heart than normal.
Your heart rate must get back to normal range (60-90bpm) after a few minutes of exercise, depending on how long your exercise is. If it takes longer or remains high, you must see a doctor.
MEASURE ENERGY EXPENDITURE
Heart rate is also used to measure energy expenditure during exercise — how much calorie you burn. This is usually called heart rate-based calorie expenditure. If you use a device to monitor heart rate, it will usually calculate how much energy you burn.
BETWEEN A CHEST-STRAPPED HEART RATE AND A WRIST-BASED HEART RATE SENSOR, WHICH ONE IS MORE ACCURATE?
Chest-strapped heart rate sensor has long been in the market, while wrist-based heart rate sensor is fairly newly.
Chest-strapped sensor measures heart rate by detecting electrical activity of the heart, while wrist-based sensor uses optical signal to detect changes in blood flow.
Some people choose wrist-based sensors because of comfort and convenience. However, the accuracy may be different. There are a lot of studies done to compare the accuracy of wrist-based and chest-strapped heart rate sensor.
At rest, both are able to accurately measure heart rate. However during exercise, wrist-based sensor’s accuracy varies. It can give up to 10 per cent variation, compared to chest-strapped sensor.
More variation is seen during high intensity exercise. Wrist-based sensor will give artefact, especially when a lot of movements are around the wrist. If the exercise requires accuracy of heart rate monitor, for example, a heart patient during cardiac rehabilitation, a chest-strapped sensor is preferred. For healthy individuals, a wrist-based sensor will suffice.
An avid sportsman who believes in the healing powers of exercise, Assoc. Prof. Dr. Ahmad Taufik Jamil is Universiti Teknologi Mara
‘s public health consultant and exercise physician. Reach him at atjamil@gmail.com