On behalf of the medical community, I would like to apologize for the confusion on how much physical activity is needed to be healthy. Every organization, every personal trainer and every doctor hans a different take on how much physical activity is really needed to be healthy.

In 2008, the first federal Physical Activity Guidelines were issued based on evidence that engaging in 150 minutes per week of moderate-intensity physical activity or 75 minutes per week of vigorous-intensity physical activity would result in substantial health benefits. This recommendation implies that the total volume of physical activity, regardless of whether it is performed at moderate or vigorous intensity, is the key for stimulating health benefits.

We are now realizing that the total volume of physical activity (number of steps per day for example) may not be the key factor. The intensity of the activity seems to be correlated with the amount of health benefit that you get from the exercise.

Research is definitely supporting the importance of vigorously intense activity in both saving time and in potentially receiving superior health benefits. In this study, one 4-minute bout of high-intensity interval training, 3 times per week yielded amazing health benefits. The most interesting aspect of this study was the benefit for cardiorespiratory fitness, glucose control, and blood pressure. Further, high-intensity interval training has been shown to benefit many different types of people with many different types of disease.

And we are just talking about 4 minutes of very intense exercise, 3 days per week…

Although I firmly believe that many people can perform high-intensity interval exercise, it may not just be preferred. In this case, at least moderately intense exercise is recommended, but how much?

Forget calories, forget minutes. The superior measure of physical activity is determined by METs (metabolic equivalents). Basically, a MET is a scientific way of measuring how much oxygen your body uses for a given activity. METs also take into account not only the total volume of physical activity that you are performing (total steps walked), but it also takes into account how fast or intense your physical activity is.

Frequently, I will talk with a patient who is frustrated with the lack of weight loss and health benefit, although he or she will walk 10,000 steps per day and exercise for 30 minutes per day for 5 days per week. My first question usually is: “How fast do you walk those steps?”

A few moments of silence typically follows. That’s because the key is intensity.

So, with all three factors (volume, time and intensity) to consider, the minimum amount of physical activity to achieve is understandably confusing. But, fortunately, the answer is in the number of METs that you can achieve per week.

Okay, so how many is needed? Per the American Heart Association:

…clinicians and allied health professionals should be strongly advocating that everyone strive to accumulate at least 500 MET minutes per week in PA of moderate to vigorous intensity.

And I would strongly recommend 3, 4-minute high-intensity interval training workout per week to really be fit…

Now the question is: How do I measure METs?

With the evolution of smartphones with built in GPS trackers, pedometers and accelerometers it is now possible, but options are limited.

In researching this article, I only came across one solitary, single app that calculates METs fairly well. This app is called Fjuul.

This app tracks your activity and awards “Fjuul points.” The faster your activity, the quicker your Fjuul points add up.

On their website, Fjuul does not specifically say that Fjuul points are equivalent to METs, but I suspected that they were. So I emailed them to inquire, and their response:

Yes-indeed, 1 Fjuul point is equal to 1 MET.

I have been using the app for a few days, and the reporting seems accurate. The interface is also simple and attractive. Even better, the app is free! Unfortunately, it is only available for the iPhone.

Short of this app, there are other ways that you can calculate METs. And while activity tracking may be frustrating and time-consuming, you may only need to track METs for a few days until you get into a rhythm of meeting your 500 MET minutes per week goal.

Take Home Point

At baseline you should achieve 500 MET/minutes (500 Fjuul points) per week of moderate to vigorous exercise to meet minimum physical activity recommendations. To really boost your health benefit without sacrificing a lot of time, I recommend performing 3, 4-minute high-intensity interval training exercises per week (which will count towards your 500 MET/minutes).

Make this your unwavering commitment, and your health will  improve drastically.