HOW TO MEASURE CARDIORESPIRATORY FITNESS
1. I PARTICIPATE IN RUNNING AND CYCLING EVENTS REGULARLY. DOES THIS ACCOUNT FOR IMPROVEMENT IN MY HEALTH STATUS?
If you exercise regularly, your cardiorespiratory fitness will improve. Running and cycling are among the best workouts to improve cardiorespiratory fitness.
Cardiorespiratory fitness is a measure of the maximum amount of oxygen taken and utilised by our body during exercise (VO2Max). The unit is ml per kg of body weight per minute.
It is not about your body shape. It is about how fast you can run or cycle and maintain that for a long period of time. In the general population, cardiorespiratory fitness declines with age at 1.6 per cent per year. Many studies have shown that cardiorespiratory fitness is an independent predictor for mortality of any causes, stronger than obesity, smoking and other risk factors.
It is a strong predictor of mortality due to heart diseases, cancer and other causes. Even if you do not suffer from weight issues, you still get a lot of benefits from exercise. This is known as the obesity paradox. An obese person whose fitness level is high has a lower risk of mortality than an unfit, lean person. The more fitness you gain, the less chances or risk you have of dying of any cause.
Another unit of fitness is metabolic equivalent (METs). One METs is the amount of energy used during sitting comfortably. One METs is equal to 3.5ml of oxygen per kg body weight per minute (3.5ml/kg/min). Studies have shown that a small increase in cardiorespiratory fitness (e.g. 1-2 METs) is associated with 10-30 per cent reduction of risk of adverse cardiovascular event.
The higher your cardiorespiratory fitness, the better health outcome you will have. A person with cardiorespiratory fitness of more than 5 METs will have more than 50 per cent risk reduction of all-cause of mortality. A cardiorespiratory fitness of more than 8 METs is associated with increased survival. Increasing cardiorespiratory fitness is important to maintain your health.
Exercising regularly will increase your cardiorespiratory fitness. Training to increase your running and cycling performance will also increase your cardiorespiratory fitness. However, you should avoid other risk factors such smoking and an unhealthy diet to reap more health outcomes.
2. HOW DO I MEASURE MY CARDIORESPIRATORY FITNESS?
Your cardiorespiratory fitness improves when your running or cycling performance increases and you are able to sustain them for a longer period of time. The gold standard to measure cardiorespiratory fitness is by direct measurement of oxygen into our body.
This is a maximal exercise testing called cardiopulmonary exercise testing (CPX). It is usually done in a special laboratory and is not easily available. Submaximal exercise test is usually done as a field test. This test includes 2.4km run/walk test and Cooper 12-minutes walk/run test.
The objective of the 2.4km test is to cover the distance in a shorter period of time and the Cooper 12-minutes test is to cover longer distance within the time.
Estimation of VO2Max is done using formulas. The result can be converted to METs value by dividing it with 3.5.
There are many non-exercise prediction equations to assess cardiorespiratory fitness. The equation use variables such as body mass index, age, gender, physical activity level, resting heart rate, percentage of body fat and smoking status.
You may check the formulas in the American Heart Association scientific statement, published in November 2016. This is the easiest way to estimate cardiorespiratory fitness.
Another practical method is by running on a treadmill as fast as you can. Enter the running data in the form available at www.exrx.net/Calculators/WalkRunMETs.html to estimate your METs value.
You may use the METs value to estimate your cardiorespiratory fitness as well as your running performance. You may also use your Garmin sports watch to measure your cardiorespiratory fitness. Garmin watches estimate VO2Max value in ml/kg/min.
3. HOW DO I IMPROVE CARDIORESPIRATORY FITNESS?
Cardiorespiratory fitness is not a surrogate measure of physical activity level. A study where self-reported physical activity and cardiorespiratory fitness are measured, cardiorespiratory fitness is shown as a stronger predictor for cardiovascular risk than physical activity level.
Cardiorespiratory fitness is influenced by genetics and physical activity level. Some people may have a low level of physical activity but their cardiorespiratory fitness is high. However, generally, the more physical activity one does, the higher the cardiorespiratory fitness.
Endurance exercises performed frequently and regularly over weeks and months will increase cardiorespiratory fitness. Exercise that involves major muscle groups (legs, arms and trunk) that is continuous and rhythmic in nature (brisk walking, cycling, running, jogging, swimming, rowing) is recommended to increase cardiorespiratory fitness.
Perform these exercises at moderate to high intensity, at a frequency of more than five days per week (moderate intensity) or more than three days a week (high intensity). The duration of exercise is 30-60 min/day (moderate intensity) or 20-60min/day (high intensity). The minimum duration is 10 minutes per session. Gradual progression of exercise volume is important by adjusting duration, frequency and intensity of exercise, until you reach the desired exercise volume per week.
Cardiorespiratory fitness appears to respond to increased intensity than increase in frequency and duration. Measure your baseline cardiorespiratory fitness. The higher the baseline cardiorespiratory fitness, the higher intensity exercise is needed. This is the value needed to increase your cardiorespiratory fitness:
a. Baseline CRF:
b. Baseline CRF: 10-14 METs. Intensity of exercise: 65-85 per cent of HRR.
c. Baseline CRF: >14 METs. Intensity of exercise: >85 per cent of HRR.
HEAL WITH EXERCISE
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 jamil@gmail.com