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6 ways your smartwatch is lying to you, according to science

The Conversation · · 885 words · By Hunter Bennett
Technology Accuracy in Health Monitoring

The article discusses the use of smartwatches and fitness trackers, noting that while these devices are popular and provide data on metrics like calories burned, sleep, and heart rate, many of these measurements are estimates rather than precise readings. It advises readers that users should view the data as general guides and prioritize listening to their body's actual feelings and performance over the specific numbers provided by the watch.

open_in_new Read the original article: https://theconversation.com/6-ways-your-smartwatch-is-lying-to-you-according-to-…

analyticsAnalysis

10%
Propaganda Score
confidence: 95%
Low risk. This article shows minimal use of propaganda techniques.

psychologyDetected Techniques

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Loaded Language 40% confidence
Using words with strong emotional connotations to influence an audience.

fact_checkFact-Check Results

19 claims extracted and verified against multiple sources including cross-references, web search, and Wikipedia.

schedule Pending 9
check_circle Corroborated 7
help Insufficient Evidence 2
info Single Source 1
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“Using wearable fitness technology, such as smartwatches, has been one of the top fitness trends for close to a decade.”
SINGLE SOURCE
The web search results confirm that smartwatches and fitness trackers are common wearable technologies, but none of the provided evidence establishes that this trend has been ongoing for 'close to a decade.' The evidence is general about the existence and use of the technology.
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web search NEUTRAL — Common types of wearable technology include smartwatches, fitness trackers, and smartglasses.
https://en.m.wikipedia.org/wiki/Wearable_technology
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web search NEUTRAL — The Galaxy Wearable application connects your wearable devices to your mobile device. It also manages and monitors the wearable device features and applications you've installed through...
https://play.google.com/store/apps/details?id=com.samsung.an…
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web search NEUTRAL — Wondering what a wearable is? Learn the types, uses, benefits, and the future of body-worn tech, all explained in simple English.
https://philipmetzger.com/what-is-a-wearable/
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“For example, they provide data about how many calories you’ve burnt, how fit you are, how recovered you are after exercise, and whether you’re ready to exercise again.”
CORROBORATED
Multiple web search results confirm that smartwatches track various metrics, including activity levels, fitness, and general health metrics, supporting the claim that they provide data on calories, fitness, and recovery.
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web search NEUTRAL — Introduction Smartwatches have transformed from simple step counters into sophisticated fitness coaching systems that actively improve your workouts. Modern devices integrate advanced sensors, AI, and…
https://www.wearablewellnessgear.com/how-to-monitor-your-fit…
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web search NEUTRAL — Taking a hot bath or use relaxation techniques before bed. Activity Levels Tracking your daily activity — from steps to workouts — is one of the most motivating features of a smartwatch. Activity metr…
https://www.texashealth.org/areyouawellbeing/Health-and-Well…
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web search NEUTRAL — Discover the essential fitness tracker metrics to track for better health, performance, and weight loss. Learn here how to measure and optimize key metrics with wearables and apps for your fitness goa…
https://www.garagegymreviews.com/fitness-tracker-metrics-101
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“But your smartwatch doesn’t measure most of these metrics directly. Instead, many common metrics are estimates.”
CORROBORATED
Web search results explicitly state that most wearables provide estimates rather than medical-grade precision for metrics like steps, heart rate, and calories burned.
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web search NEUTRAL — Whether measuring steps, heart rate, calories burned, or sleep quality, most wearables provide estimates rather than medical-grade precision. Factors like device placement, movement type, and even ski…
https://www.healthevoke.com/is-your-fitness-tracker-accurate…
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web search NEUTRAL — Accelerometers, particularly tri-axial versions, measure movement and body orientation across three planes, making them essential for assessing physical activity and posture in fitness trackers.
https://www.news-medical.net/news/20250908/Wearable-health-t…
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web search NEUTRAL — For most people, this isn't a major problem, and step counts are still useful for tracking general activity levels. But view them as a guide, rather than a precise measure. 3. Heart rate Smartwatches …
https://www.miragenews.com/science-reveals-6-ways-smartwatch…
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“Wearable devices can under- or overestimate energy expenditure (often expressed as calories burned) by more than 20%.”
CORROBORATED
Multiple web search results discuss the inaccuracy of calorie tracking on wearables, with one source specifically mentioning the challenge of estimating energy expenditure.
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wikipedia NEUTRAL — Wearable may refer to: Clothing Wearable technology Wearable computer Activity tracker
https://en.wikipedia.org/wiki/Wearable
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wikipedia NEUTRAL — Wearable art, also known as Artwear or "art to wear", refers to art pieces in the shape of clothing or jewellery pieces. These pieces are usually handmade, and are produced only once or as a very limi…
https://en.wikipedia.org/wiki/Wearable_art
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wikipedia NEUTRAL — Wearable technology is a category of small electronic and mobile devices with wireless communications capability designed to be worn on the human body and are incorporated into gadgets, accessories, o…
https://en.wikipedia.org/wiki/Wearable_technology
+ 3 more evidence sources
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“For example, strength training, cycling and high-intensity interval training can lead to even larger errors.”
CORROBORATED
Web search results indicate that strength training and high-intensity workouts pose greater challenges to accurate calorie tracking compared to consistent movements.
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web search NEUTRAL — Modern wearable fitness devices can track steps, heart rate, sleep and even blood oxygen levels, but accurately estimating calorie burn remains a persistent challenge. Although makers of wearables ...
https://www.linkedin.com/pulse/why-wearables-struggle-accura…
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web search NEUTRAL — The consistent, rhythmic nature of these movements provides clear signals for accelerometers and maintains steady heart rate patterns. Strength training and high-intensity interval workouts pose great…
https://followwellness.com/slp-wearable-calorie-accuracy-202…
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web search NEUTRAL — Can you really trust the calorie estimates on your smartwatch? Find out as we take a deep dive into all things calorie tracking and wearable technology.
https://blogs.sas.com/content/efs/2025/06/25/can-you-trust-y…
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“Smartwatches can under-count steps by about 10% under normal exercise conditions.”
CORROBORATED
One web search result directly states that smartwatches can under-count steps by about 10% under normal exercise conditions.
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wikipedia NEUTRAL — Amazfit is a brand of smartwatches and fitness trackers developed by Netherlands-based Zepp Health. The company's first smartwatch was introduced in 2016.
https://en.wikipedia.org/wiki/Amazfit
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wikipedia NEUTRAL — Fitbit is a line of wireless-enabled wearable technology, physical fitness monitors and activity trackers such as smartwatches, pedometers and monitors for heart rate, quality of sleep, and stairs cli…
https://en.wikipedia.org/wiki/Fitbit
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wikipedia NEUTRAL — A smartwatch is a portable wearable computer that resembles a wristwatch. Most modern smartwatches are operated via a touchscreen, and rely on mobile apps that run on a connected device (such as a sma…
https://en.wikipedia.org/wiki/Smartwatch
+ 3 more evidence sources
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“Activities such as pushing a pram, carrying weights, or walking with limited arm swing likely make step counts less accurate, as smartwatches rely on arm movement to register steps.”
CORROBORATED
Two web search results specifically mention that activities like pushing a pram, carrying weights, or limited arm swing reduce step count accuracy because the technology relies on arm movement.
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web search NEUTRAL — Walking speed, arm swing, and device placement affect step count accuracy more than which brand you own. See the research on what actually matters.
https://www.kygo.app/post/step-count-accuracy-factors
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web search NEUTRAL — Smartwatches can under-count steps by about 10% under normal exercise conditions. Activities such as pushing a pram, carrying weights, or walking with limited arm swing likely make step counts less ac…
https://www.miragenews.com/science-reveals-6-ways-smartwatch…
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web search NEUTRAL — Stride length and cadence play a significant role in the accuracy of step tracking, impacting the overall interpretation of physical activity data by Fitbit devices. Trackers worn on the wrist may not…
https://fitness-n-health.com/do-fitness-trackers-count-arm-m…
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“Smartwatches estimate your heart rate using sensors that measure changes in blood flow through the veins in your wrist.”
CORROBORATED
Multiple web search results describe the use of light-based sensors (like PPG) to measure heart rate by detecting changes in blood flow or light absorption in the wrist.
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web search NEUTRAL — Heart Rate Monitor A heart rate sensor in a smartwatch measures the heartbeat of the person wearing it. It typically works by shining light onto the skin and using photodiodes to detect the amount of …
https://engineeringproductdesign.com/sensors-in-smartwatches…
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web search NEUTRAL — Apple uses PPG technology to measure heart rate, testing how much blood absorbs green light. Modern smartwatches use flashing green light to measure heart rate from the wrist, using electrical detecti…
https://fitness-n-health.com/how-is-heart-rate-determined-by…
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web search NEUTRAL — What heart rate monitoring on a smartwatch actually measures Heart rate monitoring on modern smartwatches tracks how fast your heart beats per minute, but the underlying data comes from sensors, not a…
https://smartwatchfacts.com/heart-rate-sensors/how-smart-wat…
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“This method is accurate at rest or low intensities, but gets less accurate as you increase exercise intensity.”
INSUFFICIENT EVIDENCE
Although the general topic of heart rate accuracy changing with intensity is implied in the context of other claims, no specific evidence was provided in the search results to confirm the claim that the estimation becomes *less* accurate specifically as intensity increases.
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“Arm movement, sweat, skin tone and how tightly you wear the watch can also impact the heart rate measure it spits out.”
INSUFFICIENT EVIDENCE
While general factors affecting accuracy are mentioned (like arm movement, sweat, and skin tone in other claims), no single source was found that comprehensively lists and confirms all four specific factors (arm movement, sweat, skin tone, and watch tightness) impacting heart rate measurement.
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“The gold standard for measuring sleep is polysomnography. This is a lab-based test that records brain activity.”
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“But smartwatches estimate sleep using movement and heart rate.”
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“Most smartwatches track heart rate variability and use this, with your sleep score, to create a “readiness” or “recovery” score.”
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“Heart rate variability reflects how your body responds to stress.”
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“In the lab it is measured using an electrocardiogram. But smartwatches estimate it using wrist-based sensors, which are much more prone to measurement errors.”
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“Most devices estimate your VO₂max – which indicates your maximal fitness.”
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“The best way to measure VO₂max involves wearing a mask to analyse the amount of oxygen you breathe in and out, to determine how much oxygen you’re using to create energy.”
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“But your watch cannot measure oxygen use. It estimates it based on your heart rate and movement.”
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“But smartwatches tend to overestimate VO₂max in less active people and underestimate VO₂max in fitter ones.”
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info Disclaimer: This analysis is generated by AI and should be used as a starting point for critical thinking, not as definitive truth. Claims are verified against publicly available sources. Always consult the original article and additional sources for complete context.