Fitness trackers: advanced tech or just marketing?

A recent review in the European Journal of Applied Physiology examines the science behind wearable fitness trackers like Fitbits and Apple Watches, revealing that while these devices can motivate movement and raise awareness, their accuracy in measuring metrics like calories burned, VO₂ max, and sleep stages is often limited due to proprietary algorithms and a lack of individualization. The review emphasizes the importance of interpreting wearable data with caution and using it as a motivational tool rather than a medical authority.

Read the full article at https://www.paperleap.com/blog/articles/fitness-trackers-advanced-tech-or-clever-marketing-0cccui

Episode Transcript

Speaker 1 (00:00):
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(00:21):
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All the content is also available on paper leap dot com. Okay, ready,
let's start. If you've ever strapped on a fitbed, Apple Watch,
or Garmin, you know the little thrill of seeing your
step count climb, your heart rates spike during a workout,

(00:42):
or your sleep chart revealed the night's secrets. These gadgets
promise to make us fitter, healthier, and more in control
of our bodies. But here's the million dollar question. Do
they really work as advertised or are they just clever
marketing wrapped around shiny wristbands. That's the question tackled by
Ren J. Shi, Indiana University Ian g holder, Alicia A. Samsang,

(01:07):
Brittany A. Paris, and Hunter L. Paris, all from Pepperdine University.
Their review published in the European Journal of Applied Physiology
dives deep into the science of wearable fitness trackers, and
the findings let's just say they're a mix of excitement, caution,
and a reality check. Wearable fitness tech isn't new, but

(01:29):
in the last decade it has exploded. Back in twenty fifteen,
only about one in eight Americans wore an activity tracker.
By twenty nineteen, fitness surveys ranked wearables as the number
one global fitness trend, outranking yoga, weight training, and even
group classes. Today, billions of dollars are spent on devices

(01:51):
that promise to track everything from steps and calories to
oxygen saturation and stress levels. These gadgets are marketed to athletes,
but also to weekend joggers, busy parents, and even people
who simply want to sit less and move more. In theory,
that makes them powerful public health tools. Imagine millions of

(02:12):
people armed with instant feedback nudge toward healthier habits. But
apparently the science behind the numbers isn't always as solid
as the marketing suggests. Modern wearables peck a dizzing array
of sensors, including accelerometers to count steps and measure movement,
optical heart rate, sensors shining light into your skin to

(02:33):
detect blood flow, barometers in GPS to track elevation and distance,
and pulse ox simeters to measure oxygen levels. With clever algorithms,
companies claim to they can estimate calories burned, aerobic fitness,
VOTWO max, sleep stages, stress levels, and training load, how
hard your workouts are. Sounds amazing, right. The problem is

(02:57):
that most of these metrics aren't directly measured. They're estimated
using proprietary formulas that companies don't fully reveal. The researchers
comb through dozens of validation studies comparing wearables to gold
standard lab equipment. The results weren't always what you would
hope for as a user. In fact, wearables were found

(03:18):
to often miss the VOTWO max mark by more than
ten percent. That's a big error if you're training for
performance or if a doctor is trying to assess your
health risk. As far as calories burned, devices are pretty consistent.
They'll give you similar numbers if you repeat in activity,
but often inaccurate compared to lab techniques. One study showed

(03:39):
that the very people most desperate to use wearables for
weight loss those in calorie imbalance are the ones most
likely to see misleading results. In terms of step counts,
device measurements are pretty solid in the lab, but in
real life they can be wildly off. Folding laundry, your
watch may think you walked one hundred steps push a stroller,

(04:01):
it may not count steps at all. For heart rate monitoring,
chess traps remain the most reliable. Risk based sensors are
hit or miss affected by skin tone, sweat movement type,
and even how tightly you wear the band. Finally, in
regard to sleep and stress, only a tiny fraction of
consumer devices have been formally validated against gold standard sleep

(04:23):
studies or clinical stress measures. The big picture, these trackers
often work well enough to give you a general sense
of trends, but they shouldn't be treated like medical devices.
While there are several reasons. First, companies guard their formulas
like trade secrets, making it hard for independent scientists to

(04:44):
evaluate or improve them. Second, many devices apply the same
one size fits all math equations to everyone, ignoring differences
in age, sex, fitness level, and even biomechanics. Finally, lab
tests happen on treadmill and bikes. Real world activity includes dancing,
carrying groceries and chasing kids, movements that confuse sensors. Despite

(05:08):
their flaws, people love wearables. In a twenty nineteen survey,
the top reasons users gay for wearing them were as follows.
Forty seven percent of people use them to manage fitness,
forty five percent to feel in control of health, sixty
percent to track steps, forty two percent to monitor their
heart rate, and forty two percent to control how many

(05:30):
calories they consume. In fact, many users say they'd even
pay extra to have doctors or health coaches interpret their
wearable data. And here's where the sticks rise. If health
professionals start relying on flawed numbers, patients may get misleading advice.
So is it advanced tech or advanced marketing? The author's

(05:53):
verdict is nuanced. On one hand, wearables have revolutionized the
way people engage with their health, motivate movement, provide awareness,
and can sometimes detect meaningful changes over time, like a
sudden rise and resting heart rate that signals illness. On
the other hand, the lack of accuracy, transparency, and validation

(06:14):
means we should treat the numbers with caution. A fitbit
telling you you've burned six hundred calories doesn't mean you
should eat a slice of cake guilt free. The review
definitely calls for better standards. Just as new drugs go
through rigorous trials, wearables could benefit from standardized validation before
bold claims hit the market. Also, there should be more transparency.

(06:38):
Companies should open up their algorithms for scientific testing, and finally,
one size fits all systems should instead make space for individualization.
Devices need to account for personal differences in physiology and activity.
Until then, the best advice is this, Use your wearable
as a motivational coach, not a medical oracle. Look at

(07:01):
long term trends, not single numbers. Treat it like a
compass pointing you in the right direction, not a GPS
with exact turn by turn accuracy. Indeed, wearable fitness trackers
are here to stay. They cannot just toward healthier habits.
Help us notice patterns and keep us accountable. But if
you're relying on them to tell you exactly how many

(07:23):
calories you've burned, how stressed you are, or how well
you slept last night, take those numbers with a grain
of salt. As the authors put it, good science isn't
always good marketing. And good marketing isn't always good science.
That's it for this episode of the paper Leap podcast.

(07:43):
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