4 Reasons Why Your Fitness Wearable Won’t Get You Stronger

I’m an elite powerlifter. I’ve also worked in the health and fitness wearable space. Yet I don’t wear a fitness wearable when I work out. Here’s why.

Look down at your wrist…are you wearing a fitness wearable? I may know a thing or two about that technology. During my career, I ran the clinical studies for the first FDA approval for Verily’s (Google’s former life sciences division) health monitoring watch.

Yet despite this scientific experience and an alter ego as a professional powerlifter, I don’t use a fitness wearable … and not because I am trying to avoid a watch tan.

Look at professional strength athletes. How many of them are wearing a Whoop, Apple, Fitbit, Oura ring or Polar when they work out? In my decade as an elite strength athlete (powerlifting, Olympic weightlifting, and bodybuilding) I can count on one hand how many I have seen. These fitness device companies have added features that are impressive like heart rate, heart rate variability, sleep tracking, workout trackers, and calories burned. Yet how many of these metrics improve your athletic performance?

In my personal experience, these watches and rings feel more like expensive toys than tools for the gym.

Fitness wearables don’t integrate smoothly into many strength workouts. These watches can’t be worn during lifting activities that require wrist wraps, such as Olympic lifting and most powerlifting movements; fitness tracking rings can interfere with gripping barbells or dumbbells. So for a wearable device to be worth the disruption to my lifting routine, it needs to provide personalized and specific recommendations that guarantee improved performance.

Let’s explore 4 metrics these fitness devices measure and why these rings and watches may not be helpful to you.

1. Heart Rate

Every fitness wearable, at minimum, is expected to track heart rate continuously and in real time. An athlete (or anyone, really) can use this information to understand how intense the workout is or when to start the next set. However, the accuracy of heart rate measurement relies heavily on the device making full contact with the skin. In cases where the device does not fit properly and moves around or something like hair or sweat gets in the way of skin contact, accurate measurements become difficult or impossible.

While heart rate can be a useful indicator of overall intensity, heart rate alone does not always directly correlate to workout intensity for weight training. For many lifters, heart rate may not be as accurate as other commonly used metrics, such as Rate of Perceived Exertion (RPE) that measures a person’s physical sensations because RPE takes into account the individual’s effort level. Heart rate can also be affected by many other factors such as stress, fatigue, and hydration — meaning that your heart rate can be elevated for reasons other than your workout.

2. Heart Rate Variability

Heart Rate Variability (HRV) is another popular metric used to market fitness wearables. This is the measure of the time variation between heartbeats, which indicates recovery and stress levels. A higher score indicates a relaxed state while a low HRV score could indicate that an athlete is under heavy stress, physical or mental, which could affect their performance and recovery time. This information could lead them to adjust their training schedule, incorporate more recovery and rest days, or modify their training intensity to avoid overtraining or injury.

HRV measurements are derived using heart rate data, so this measurement is limited by the accuracy of the heart rate sensor. Also, a low HRV reading cannot distinguish if somebody is just under stress or in a state where they need to recover. Someone could be in the middle of a workout with plenty of energy yet still get a lower than usual HRV reading. Conversely, you could still be really sore from yesterday’s workout and have a high HRV because you slept well last night.

3. Sleep

Most fitness wearables also offer sleep tracking features, combining the use of accelerometers to track movement and the heart rate sensor to monitor heart rate. However, its accuracy can be heavily influenced by factors such as sleep position and restlessness. As a result, the feature assumes that if your heart rate is low and you are lying relatively still, you are asleep. So if you’re a peaceful insomniac like me who lies still staring at the ceiling awake for hours wondering why you can’t fall asleep, your sleep results will be inaccurately generous by several hours.

While the numbers generated by a sleep tracker may gamify the concept of sleep, most people intuitively recognize if they have not slept well. In such cases, a tracker is often unnecessary to convey the obvious.

4. Calories burned

Sure, fitness trackers can now tell you how many calories you burned — but they’re probably wrong. Several studies have shown that smartwatches and fitness trackers can be anywhere between 40% to 80% off one’s actual calorie expenditure. These devices estimate calories burned based on generic formulas using heart rate, reported body weight, and activity level. The accuracy of the formula, however, can fluctuate from person to person based on movement type, actual body weight, and body composition.

Since activity level is calculated solely based on the movement of the hand movement wearing the device, activities involving heavy wrist movement, such as dusting furniture or weightlifting, can lead to inaccurate measurements. In fact, once while wearing an activity tracking watch, the watch mistook my aggressive gesturing as exercise. The same thing happened while eating! So if you’re a very expressive person (or a glutton), be prepared for some false positives.

More importantly, this measurement does not give a complete picture of calories burned; a significant amount of calories burned from an intense workout are burned in the hours and days after the workout in the form of respiration, muscle repair, and replenishment, and body temperature elevation.

So if you’re looking to lose weight, you may want to take your fitness tracker’s calorie burn estimates with a grain of salt.

If you are into fitness, you want higher quality action steps from your fitness wearables, not numbers for the sake of numbers. I think we would all prefer our fitness wearable to tell us exactly what to do to lose fat and get stronger than tell us how many calories from fat we burned. But since wearable fitness trackers can’t yet offer this, what we’re left with is a lot of data that is fun to track but is not that useful.

As a high performing strength athlete, I think I can speak for those of us who are always striving for more when it comes to our lifts. What do we want? We would love a device that tells us the max weight we should lift today based on the quality of our warmup. But I don’t see that happening anytime soon.

Until then? I’m keeping my wallet shut (and my arm and fingers fitness accessory-free).