How to use your activity monitor data well

Activity monitors and smartwatches from manufacturers like Fitbit or Apple collect a wealth of data on your health: active minutes, number of steps taken, heart rate… How to interpret them? Are they all useful and reliable? Here is the opinion of some experts.

The number of steps and minutes of physical activity
Calories and weight loss
Heart rate
Sleep tracking
What about your privacy?

Despite the efforts of manufacturers of activity monitors or smart watches, such as Fitbit and Apple, to properly present the puzzling amount of information collected and to explain this data in their applications, one can get confused.

What info should you take into account? Can you trust it?

To help you better understand your physical activity monitor and how to use it properly, we’ve reviewed the main categories of data it presents. As you will see, not all of them are useful, but some could be used to improve your health.

“What is good with these devices is that we have a feedback immediate, for example on the number of steps walked in a day, underlines Yvan Campbell, kinesiologist at the Institute of kinesiology of Quebec. It’s a good tool to improve your lifestyle. ”

Whether you are an athlete looking for new performance or a less active person anxious to improve their health, you will find valuable advice in our article.


The number of steps and minutes of physical activity

All activity monitors count the number of steps using an accelerometer and have basic goals to achieve, such as 10,000 steps per day. This emblematic number would have appeared in 1965, the year in which a Japanese manufacturer launched the Manpo-kei pedometer (“10,000 steps counter” in French) on the market.

“The 10,000 steps per day is an interesting concept, but what matters most is the number of minutes of exercise per day,” explains Martin Juneau, cardiologist and director of prevention at the Heart Institute. from Montreal. The more we do, the more health benefits we derive, such as the prevention of cardiovascular disease. But most studies show that after the equivalent of an hour and a half of walking per day, which equates to about 10,000 steps, you have no more significant gain. ”

“This type of objective is a good starting point, but it must be adjusted to the person’s motivation, to their experience in physical conditioning and to their pathologies, if applicable”, emphasizes Yvan for his part. Campbell.

Rather than a certain number of steps, the World Health Organization (WHO) recommends that adults between the ages of 18 and 64 do at least 150 minutes of intensity endurance activity during the week. moderate (such as walking) or at least 75 minutes of sustained intensity endurance activity (such as running), or an equivalent combination of moderate and sustained intensity activity. Recent Fitbit models also count these periods of physical activity under the name “minutes in active zone”.

Calories and weight loss

By taking into account various factors (height, weight, age, sex, movements, etc.), activity monitors also estimate the number of calories burned by your body in a day. “The estimate of calories burned is pretty rough, but it can help motivate yourself,” says Dr.r Juneau.

By the way, all the experts we spoke to agree on this point: if you want to lose weight, you must first focus on your diet, for example by reducing your portions or opting for low-fat meals. calories.

In addition, increasing your level of physical activity will help you reach your goal. According to Mickaël Martin, kinesiologist at the University Institute of Cardiology and Pneumology of Quebec, you have to walk between 14,000 to 16,000 steps per day to lose weight, which corresponds to more than two hours of walking. Of course, if you do a more strenuous activity, such as running, you will be able to expend the same amount of energy in less time.

Also consider incorporating strength training into your physical activity program. “With more muscle mass, you increase your basal metabolism and thus burn more calories,” explains Yvan Campbell.


Heart rate

Multiple activity monitors continuously track your heart rate by measuring blood flow to the wrist, using LED lights.

According to the Montreal Heart Institute, the heart of an adult in normal physical condition beats between 50 and 80 times per minute at rest. In an elite athlete, the heart rate can be as low as 30 beats per minute (BPM) at rest. Indeed, the stronger a heart, the less often it has to beat to circulate blood. So, if you train your cardiovascular system, you might see your resting heart rate decrease over time.

Several activity monitors set personalized heart rate zones based on your age and resting heart rate. For example, Fitbit might determine that between 100 and 125 BPM, you are in the fat loss zone; that between 126 and 159 BPM, you are in cardio zone, and that at more than 159, you are in maximum zone.

To improve your cardiovascular health, training in the cardio zone will obviously be the most useful. If you do high-intensity interval training (for example, running at a comfortable pace with short sprints), you might spend a few minutes in the maximum zone.

As for the fat elimination zone, it is not very relevant, according to Mickaël Martin. “It comes from an old scientific literature that at low intensity you burn more fat and at high intensity you burn more sugar. This is still true, but in order to burn enough calories at a low intensity to lose weight, you will have to exercise for hours and hours. ” In short, to lose weight, it is better to train in a cardio zone.

According to all the experts consulted, if you want to train seriously according to your heart rate, it is better to opt for a chest strap, a device that measures the heartbeat in the chest rather than the wrist, a popular method. more precise.


Vo2Max is the maximum flow of oxygen that your body can consume during exercise. For example, for a 45-year-old woman, a VO2Max of less than 21 milliliters per minute per kilogram (ml / min / kg) will be rated very low, while it will be considered excellent if it exceeds 38 ml / min / kg. According to the Dr Martin Juneau, the VO2Max is one of the best indicators of your health.

Normally, we determine the VO2Max on a treadmill, with a mask that measures gas exchange during exercise. Rather, activity monitors estimate it based on your weight, age, gender, and resting heart rate. According to the Dr Juneau, the original version2Max displayed by monitors is therefore very approximate. Note that the VO2Max may be presented by another name, such as “Cardio Fitness Level” in the Fitbit app.

If you increase your level of physical activity, you might see the VO2Max indicated by your monitor will increase a little. But your expectations must be realistic. According to Dr Juneau, training helps increase VO2Max of about 10 to 20%.


Sleep tracking

Most activity monitors track sleep using measurements like body movement and heart rate. They estimate the duration of sleep, the time spent awake during the night as well as the length of the different phases of sleep.

According to Julie Carrier, sleep researcher at the Hôpital du Sacré-Cœur-de-Montreal and at the Research Center of the University Institute of Geriatrics of Montreal, very few scientific studies have been carried out to validate sleep monitoring carried out by activity monitors. It is therefore impossible to say whether the generated data is reliable or not.

Also, according to the researcher, knowing how long you spend in deep or REM sleep is of no use. “Scientifically, I can’t tell you, depending on your age, that you should spend so much time in this or that phase of sleep. All we know is that an adult should sleep between seven and nine hours a night. ” Her advice: give yourself plenty of time to sleep, and your body will take care of the rest. Do you have insomnia? See our article on the subject.

Note that some activity monitors now measure oxygen saturation in the blood. Normally, this varies little (from 95 to 100%), unless you are sick or have sleep apnea. “It’s an interesting avenue for detecting sleep apnea,” recognizes Julie Carrier. But there are other symptoms to watch out for, such as daytime sleepiness, snoring and respiratory arrest at night. ”

What about your privacy?

Activity monitors collect a lot of data that manufacturers can use. For example, Apple and Fitbit are collaborating with researchers to conduct scientific studies on different health issues.

According to the manufacturers, the information collected by activity monitors is anonymized and aggregated, meaning that there should be nothing to link health data to a particular person.

According to Stéphane Hamel, consultant specializing in cybermetry, the confidentiality policies of activity monitor manufacturers are drafted in such a way as to allow this kind of use of data. “The problem is, by using these products, people are sharing information without knowing it, without scrutiny and without control,” he says.

Indeed, manufacturers of activity monitors offer few privacy settings. If you have any concerns in this regard, it is probably best not to use this type of device.

If necessary, do not hesitate to consult a kinesiologist, who can teach you how to train according to your perception of the effort, which does not require an activity monitor.


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