You’ve been instructed to walk on the treadmill for 30 minutes every day. You saunter along listening to music, wondering what to have for lunch. After all, it is minimum 30 minutes/day to maintain health, isn’t it? No problem, you can do it.
The media screams that a lower intensity workout burns more fat. What could be better? You stroll around the park barely working up a sweat. This seems pretty straightforward and easy. Why didn’t you think of it before?
While it is true that a longer duration, lower intensity workout derives the energy required for that particular exercise primarily from your fat stores, it is the total amount of energy expended versus energy consumed at the end of the day/week/month that really matters and determines your weight.
So let us assume that you walk at 3km/hour and burn about 150–200 calories in 60 minutes. Most of those calories may have been derived from your fat stores as you are working out at a lower intensity; however, it is long-term calorie deficit that is crucial in weight loss and more importantly, weight management. If, for instance you had worked at a much higher intensity during that one hour, burning about 300–500 calories, in the long haul, the chances are you will be able to maintain a calorie deficit which is essential for weight loss. The accumulation of calories burnt over an extended period of time is more important than calories expended per individual session.
Another important finding needs to be highlighted here. If you are capable of working at higher intensities, then doing so will cause a continued increased consumption of energy and therefore calories post workout. The higher the intensity of the workout, whether cardio or weight training, the higher the calorie-burn post exercise, sometimes persisting for as long as 6–12 hours. This increase although marginal is valuable for fat loss. This is called EPOC or Excess post-exercise oxygen consumption. EPOC is increased after higher intensity workouts and after strength training.
What is a MET?
The intensity of your workout is defined by MET, the acronym for Metabolic Equivalent. It is the ratio of your working metabolic rate relative to your resting metabolic rate. The energy expended at rest is generally referred to as 1 MET. As you increase physical activity your METs increase. Gardening, for instance, could have you working at a MET of about 4–5. A stroll in the park could be anywhere from 3–5 METs. An activity with a MET of 4 means you are working four times harder than while at rest.
How is your required MET calculated?
The required MET is calculated depending on age and basic lifestyle of the individual (sedentary/ highly active etc). This is relevant only to physiologically normal people. Those with heart problems, post-surgery or physically-challenged are to be treated differently, and this involves a different set of goals, objectives and working principles.
A fitness professional should be able to educate you on your required METs during your workout to attain maximum benefits. Each activity (walking, running, cycling, strength training and so on) will have a different MET. Running for instance has more METs than walking.
When you start watching your METs, initially, achieving your required MET may seem a herculean task. You didn’t anticipate how dreadful this would feel. How are you supposed to keep this up? As your fitness levels increase, it gets easier and more manageable. It gives you a goal to work towards a MET that is easily measurable and reproducible since it is denoted by a simple number on your cardio machine.
What if you can’t calculate your MET?
Another way of assessing the intensity of your workout is by using the rate of perceived exertion or RPE scale. This is a subjective measure of how you feel during your workout. On a scale of 1–10, sitting stationary would be a 1. Moderate activity like moving around the house without breaking into a sweat would be about a 5 on the scale. As you increase intensity of a workout, you get more breathless, and your heart begins to beat faster to accommodate the increased workload. At an intensity of about 7, you will be able to talk but not more than a sentence or so. At 8–9 you will be unable to say more than a word or two while working out. 9–10 is all out activity; it does not allow you to even say a word. Higher intensities cannot be sustained for long. A 100-meter sprint would be an intensity of 9–10.
How do you identify your MET in a gym setting?
Most cardiovascular equipment in gyms have MET settings as an option on the control panel and can be easily viewed while training. You will notice that you can increase/decrease your MET by increasing the speed, incline or workload on the machine. Over time, an experienced exerciser can easily recognise his working MET subjectively (by the way he feels) even while exercising outdoors without the aid of a machine.
You may not be able to sustain your required metabolic equivalent for the entire duration of your workout. The idea is to try and get to it from time to time. In other words, push yourself beyond your comfort zone every few minutes during your workout to reach your required MET. This is called High-intensity Interval Training or HIIT and is highly effective in fat loss as well as producing remarkable improvement in cardiovascular endurance.
- Low intensity: This is about a Level 3–5 on the perceived exertion scale (PES). You could work at this intensity when you’re warming up or if you’re doing a longer workout, like a long bike ride or slow, relaxed walk. This might also be an intensity you work at if you take walks throughout the day.
- Moderate intensity: This is about a Level 5–7 on the PES and where most of your workouts should fall. This would be considered being in a space where you can talk, but only a sentence or so. Try this level about 3–4 times a week.
- High intensity: This is about a Level 8–9 on the PES, and a level you can only work at for very short periods of time. You might work at this intensity when doing high intensity interval training, for instance. This can be done once or twice a week with lots of rest in between.
The human body is enormously capable of improvement — provided, we challenge it. Maintaining one’s workout intensity levels at a humdrum, comfortable level throughout our workout will only create monotony and set the stage for what is referred to as “hitting the wall” in physical fitness terms. You will see no progress. On the other hand, being able to achieve your MET often and being able to maintain it longer will give you a sense of achievement and satisfaction and urge your body to higher limits.
If you happen to fall off the wagon and haven’t seen your training shoes in a while, it is always advisable to start at a lower intensity and work your way up once again. Fitness levels tend to deteriorate with neglect, particularly if you are a beginner and hasn’t built up adequate fitness levels. It is unrealistic and not very prudent to expect to resume where you left off after a long sojourn.
There will be days when all you want to do is stroll, go through a gentle stretch or practise relaxation. That’s reasonable and acceptable.
In fitness, there is always room for improvement. Aiming to improve fitness levels is one of the goals to set. This way, progress can be measured, and you will remain motivated to continue to exercise even if the weight on the scale doesn’t move for some time. I always tell clients not to focus solely on weight, but also pay attention to their fitness levels which will improve provided they challenge the body adequately. Try increasing the distance covered in the same time. Try including inclines on your walk. Try lifting heavier weights.
The author is a lifestyle medicine physician.
MET is the energy you use while at rest
MET is approximately 3.5 ml of oxygen consumed per kg body weight per minute
Your required MET is derived at by taking into consideration your age and lifestyle.
Most cardio equipment in a gym setting will be able to indicate the MET you are working at.
If you cannot calculate your MET, use the Rate of Perceived Exertion to assess the intensity of your workout and aim to increase that intensity from time to time.