The Accuracy of Smart Watches
The market for smart watches and activity trackers has exploded in recent years. Products like the apple watch, fit bit, Garmin, and others have risen to stardom in the fitness community.
They really come off as miraculous devices. Some of the data they claim to be able to tell you include heart rate, electrocardiogram, steps, sleep duration, sleep quality, active calories burned, resting calories burned, and plenty more.
However, they do tend to be rather expensive. Depending on what you buy, they can range anywhere from $100-$900. Even if you go with the cheapest one, you should be confident that they can deliver what they promise.
In this article, we’ll talk about if they work and how accurate they are, if they are worth it based on what the research says, and some more of my personal thoughts on them.
So, how accurate are they?
This is actually a topic that has received a lot of attention in the research. If they are accurate, then they can have a lot of helpful implications in not just fitness endeavors, but for health purposes as well. So, how do they hold up?
A study from Xie et al. [1] Looked at just this. Some areas of the watches were very accurate and others were off by a lot more than you think. For heart rate, step count, and distance (in terms of a run, swim, bike, etc.) the watches were very accurate or off by just a little bit.
However, the watches were VERY inaccurate in measuring how many calories were burned. Other studies show that the apple watch specifically tends to be anywhere from 30-90% inaccurate [2]. This means if it tells you that you burned 500 calories in a workout, you likely actually only burned 50-350 calories in that workout.
The fact that they are this inaccurate in calorie expenditure can be a big problem. As you may know, in order to lose weight, you must burn more calories in a day than you eat (i.e. calorie deficit). Many people don’t believe this and end up falling victim to fad diets, demonizing food groups, and snake-oil nutrition courses. Often times, the reason people don’t believe in “calories in versus calories out” is because they think they are putting themselves into a calorie deficit but never actually do.
You see, many people tend to greatly overestimate how many calories they burn and greatly underestimate how many calories they are eating. Lichtman et al. [3] studied what the difference is between how many calories people think they are eating versus how many calories they are actually eating. On average, the subjects actually ate 47% more calories than they thought they were eating. Many who reported eating 1200 calories a day were actually eating 2000 calories in that day.
If you take someone who thinks they are eating half of what they actually are, and then make them think they are burning more calories than they actually are, then they are doomed. If you are in the market for a watch like this, whether it’s apple, Fitbit, Garmin, or whoever else, I think this is a major consideration to have in mind.
Are they worth it?
To fully answer this question would likely need some personal context. However, I think it really boils down to what you want out of the watch. Gadgets like the apple watch have a plethora of features that are not fitness related, so for the purpose of this article we will only talk in terms of fitness.
Based on what the research says on their accuracy in how many calories you burn, I would just throw that feature out the window. Unfortunately, there is no consumer device available yet that can accurately measure how many calories you are burning in a day. For tips on how to get an idea of this, check out the linked article below.
Related: Macronutrient Basics: Understanding Carbs, Fats, and Protein
As said before, these types of watches tend to be accurate in regard to heart rate, step count, and distance. This means that they are likely helpful to some, but not others.
Let’s say you are someone who primarily only does resistance training (weight training, etc.) and has overall good health. In this case, they are likely not worth it due to the price point associated with them. Think about it this way, you’d be paying $200-$400 for a watch that will not give you any data that is conducive to your training. If you bought it for the social features that an apple watch has, that’s a different story. However, the watch would not make sense otherwise for this type of individual.
So, who is it worth-it for? Two types of people primarily. I would argue that these types of watches are worth it for endurance athletes and those who are trying to monitor or improve their cardiovascular health.
Let’s say you want to improve your running. Having a good idea of how far you are running, how long it is taking you to run that distance, and your heart rate throughout that run, are all invaluable data to monitor over time. If you want to improve your mile time, then being able to see how it changes over time can be a huge help.
Further, one of the main adaptations from improving your cardio is your heart rate decreasing, both at rest and during your training. So, if over time you notice your resting heart rate dropped from 80 beats per minute to 60 beats per minute, then you know your endurance is improving.
Related: How Cardio Affects Your Body
If you are trying to monitor or improve your cardiovascular health, knowing your heart rate and step count can be very helpful as well. Having a daily step count between 8,000-10,000 steps per day has been shown to be helpful in fighting off heart disease, and having the watch to make sure you hit those numbers can help keep you on track.
Further, decreasing your resting heart rate is another sign of improved heart health. Having a close eye on this data point can give you a glimpse into how you are doing day-to-day.
My personal opinion and what I use
I’ve been training my endurance most of my life through soccer and triathlons, and currently do 50/50 split of running and weights for my own training. As a result, I have felt that one of these watches is worth the purchase to me.
The watch I personally use is the Vivoactive 4 from Garmin.
The main data that I track are distance, time, average pace, best pace, average speed, best speed, average heart rate, and max heart rate. Understanding these data points really gives a clear view into my performance in each run and how my performance changes over time.
For measuring stress, I am not too sure what metric they use to measure it. However, the number value it gives always seems to rise when I get sick (cold, covid, etc.), so it seems to be able to pick up the trends of my stress levels at least.
The Garmin Vivoactive 4 is the only smart watch like this that I have ever used, and is therefore the only one I can personally vouch for. However, as an endurance athlete, I have nothing but good things to say about it. If you train your endurance in any capacity whether it is running, swimming, biking, etc., I would recommend this watch.
References
Evaluating the Validity of Current Mainstream Wearable Devices in Fitness Tracking Under Various Physical Activities: Comparative Study
PubMed ID: 29650506
Accuracy of Apple Watch Measurements for Heart Rate and Energy Expenditure in Patients With Cardiovascular Disease: Cross-Sectional Study
PubMed ID: 30888332
Discrepancy between self-reported and actual caloric intake and exercise in obese subjects
PubMed ID: 1454084
