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            <![CDATA[ Wearables - freeCodeCamp.org ]]>
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            <![CDATA[ Browse thousands of programming tutorials written by experts. Learn Web Development, Data Science, DevOps, Security, and get developer career advice. ]]>
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                <![CDATA[ Wearables - freeCodeCamp.org ]]>
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                <title>
                    <![CDATA[ Sleep Tracking, Bluetooth Signals, and EMF: What Every Wearable User Should Know ]]>
                </title>
                <description>
                    <![CDATA[ You take off your shoes before bed. You probably don't take off your smart ring or your watch. Most of us sleep with a Bluetooth-enabled device sitting a few millimeters from our skin, all night, ever ]]>
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                <link>https://www.freecodecamp.org/news/sleep-tracking-bluetooth-signals-and-emf-in-wearables/</link>
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                    <category>
                        <![CDATA[ Wearables ]]>
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                    <category>
                        <![CDATA[ Health Tech  ]]>
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                    <category>
                        <![CDATA[ bluetooth ]]>
                    </category>
                
                    <category>
                        <![CDATA[ Bluetooth Low Energy ]]>
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                <dc:creator>
                    <![CDATA[ Shradha Puri ]]>
                </dc:creator>
                <pubDate>Tue, 23 Jun 2026 15:45:55 +0000</pubDate>
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                    <![CDATA[ <p>You take off your shoes before bed. You probably don't take off your smart ring or your watch. Most of us sleep with a Bluetooth-enabled device sitting a few millimeters from our skin, all night, every night, while transmitting small amounts of radiofrequency (RF) waves and collecting sleep data.</p>
<p>This thing is quietly recording your heart rate and movements while you’re sleeping. So it's a valid question to ask whether the wireless signals or electromagnetic field (EMF) radiation it emits could interfere with sleep quality, disrupt hormones such as melatonin, affect circadian rhythms, or produce other biological effects over time.</p>
<p>The concerns are part of the wider discussion on EMF’s and wireless technology. Although all smartphones, Wi-Fi, and wearables emit RF waves, the amounts of energy used and how they work can be quite different. Understanding what your sleep tracker is actually doing helps put those concerns into context.</p>
<h2 id="heading-table-of-contents"><strong>Table of Contents</strong></h2>
<ul>
<li><p><a href="#heading-how-sleep-trackers-measure-sleep">How Sleep Trackers Measure Sleep</a></p>
</li>
<li><p><a href="#heading-whats-actually-transmitting-from-your-ring-or-watch">What's Actually Transmitting From Your Ring or Watch</a></p>
</li>
<li><p><a href="#heading-how-that-stacks-up-against-safety-limits">How That Stacks Up Against Safety Limits</a></p>
</li>
<li><p><a href="#heading-where-the-melatonin-research-gets-misapplied">Where the Melatonin Research Gets Misapplied</a></p>
</li>
<li><p><a href="#heading-what-the-latest-research-actually-says">What the Latest Research Actually Says</a></p>
<ul>
<li><a href="#heading-the-pushback">The Pushback</a></li>
</ul>
</li>
<li><p><a href="#heading-what-this-means-for-how-you-wear-it-at-night">What This Means for How You Wear It at Night</a></p>
</li>
<li><p><a href="#heading-the-bigger-risk-isnt-the-radio">The Bigger Risk Isn't the Radio</a></p>
</li>
</ul>
<h2 id="heading-how-sleep-trackers-measure-sleep"><strong>How Sleep Trackers Measure Sleep</strong></h2>
<p>Before discussing the impact of signals and EMF, we should know what exactly happens when a device monitors your sleep.</p>
<p>Sleep trackers rarely actually measure your sleep but rather use sensors to track movements, heart rate, heart rate variability (HRV), breathing rate, temperature, and more.</p>
<p>The software analyzes data and distinguishes between states like awake, light sleep, deep sleep, and REM sleep. As opposed to professional polysomnography, sleep tracking devices don't measure brain waves and so can't actually observe sleep. They only make an educated guess.</p>
<p>This is critical to understand, because it's not the Bluetooth radio itself that measures your sleep, but rather sensors.</p>
<h2 id="heading-whats-actually-transmitting-from-your-ring-or-watch"><strong>What's Actually Transmitting From Your Ring or Watch</strong></h2>
<p>The chip in your Oura, Ultrahuman, or Apple Watch communicates with your phone via Bluetooth Low Energy (BLE). BLE was designed with a power budget rather than a performance budget because, in this case, power is more important than range when you have the receiver just a few inches away, in your pocket or on your nightstand.</p>
<p>The transmit power, according to the <a href="https://pmc.ncbi.nlm.nih.gov/articles/PMC5751532/">Bluetooth specification</a>, is capped at 100 milliwatts. But most chips used by consumers are well below the maximum power limit, often at 1-10 milliwatts.</p>
<p>By contrast, a cell phone during a voice call can transmit up to <a href="https://www.rfpage.com/is-bluetooth-safe/">250 to 2,000 milliwatts</a>. You're not carrying a miniaturized cell tower, you're carrying an item that transmits in bursts of low-power signals.</p>
<h2 id="heading-how-that-stacks-up-against-safety-limits"><strong>How That Stacks Up Against Safety Limits</strong></h2>
<p>The SAR metric is used to quantify the amount of RF energy tissue absorbs. This metric is measured in watts per kilogram. The <a href="https://support.realwear.com/knowledge/specific-absorption-rate-sar-information">Federal Communications Commission (FCC)</a> caps the SAR level to 1.6 W/kg averaged over 1 g of tissue. But according to International Commission on Non-Ionizing Radiation Protection (ICNIRP) standards, the average SAR should be maintained at 2 W/kg averaged over 10 g of tissue.</p>
<p>No wireless communication device will be certified and made available on the market unless it meets the criteria of the SAR metric.</p>
<p>In the United States, the SAR limit for wrist-worn devices is 4.0 W/kg. According to Apple's <a href="https://wearablexp.com/smart-watches/does-apple-watch-emit-radiation/">Apple Watch RF exposure data</a>, the watch has a reported SAR value of approximately 0.17 W/kg, while Oura reports a SAR value of 0.0003 W/kg for the Oura Ring. Both are well below regulatory limits, illustrating just how little RF energy these wearables typically emit.</p>
<p>According to an engineering evaluation published in 2024 by <a href="https://arxiv.org/pdf/1912.05282">Kim, Sharif and Nasim</a>, SAR levels associated with commercial wearable technology operated at 2.4 GHz have been found to comply with the regulatory threshold and the safety guideline at the distance of skin contact.</p>
<h2 id="heading-where-the-melatonin-research-gets-misapplied"><strong>Where the Melatonin Research Gets Misapplied</strong></h2>
<p>Melatonin is the natural hormone responsible for regulating your sleep-wake cycle, which is why it has been frequently mentioned in the context of the relationship between EMFs and sleep. Indeed, there have been numerous studies in the past indicating that exposure to specific forms of electromagnetic fields might have an impact on melatonin production, circadian rhythms, or oxidative stress.</p>
<p>But the results from these studies have been quite mixed. Some research has found a notable effect, while others have found no significant effect at all. Most importantly, most studies that are constantly being cited refer to extremely low-frequency (ELF) fields generated by power lines, electrical wiring, and household electricity in general and not the Bluetooth device radiofrequency signals.</p>
<p>That research is real, but it often concerns extremely low-frequency (ELF) fields, those at 50-60 Hz found in power lines and electrical wiring, rather than the 2.4 GHz radiofrequency used by your Bluetooth ring. These are different parts of the electromagnetic spectrum with different interaction mechanisms.</p>
<p>Citing ELF melatonin studies to explain RF wearable exposure is a bit like citing research on UV exposure to explain what your microwave does. Related field, wrong frequency range.</p>
<h2 id="heading-what-the-latest-research-actually-says"><strong>What the Latest Research Actually Says</strong></h2>
<p>The strongest evidence we have today comes from a series of systematic reviews commissioned by the <a href="https://pmc.ncbi.nlm.nih.gov/articles/PMC12490090/">World Health Organization</a>.</p>
<p>There were several reviews published between 2024 and 2025 which aimed to assess whether RF-EMF (Radiofrequency Electromagnetic Fields) exposure was connected with outcomes such as sleep disorders, headaches, and nonspecific symptoms.</p>
<p>No evidence suggesting a cause-and-effect relationship between RF-EMF exposure below current safety thresholds and sleep disorders was reported by either experimental or observational research.</p>
<p>This certainly doesn't solve the problem because of the uncertainty of the evidence. And this is quite low due to challenges in estimating actual RF exposures experienced by people. We're all surrounded by various signals emitted by our smartphones, Wi-Fi routers, laptops, cellular towers, and so on.</p>
<p>The conclusion is relatively simple, though: there's currently no evidence that would show that RF exposures using Bluetooth disrupts people’s sleep. That being said, researchers are still actively exploring the issue.</p>
<h3 id="heading-the-pushback"><strong>The Pushback</strong></h3>
<p>Not everyone agrees with these findings. Some researchers claim that WHO review fails to give enough weight to certain studies and that research findings on the subject are still lacking.</p>
<p>This criticism targets the whole body of work on RF-EMF radiation since most of them are based on mobile phones rather than wearable technology.</p>
<p>The debate is ongoing, but present research doesmn't show any disruptions caused by wearables with Bluetooth functionality.</p>
<h2 id="heading-what-this-means-for-how-you-wear-it-at-night"><strong>What This Means for How You Wear It at Night</strong></h2>
<p>If the thought of wearing a sleep-tracking wearable next to your body for a full eight hours leaves you feeling uncomfortable, the quickest solution won’t be getting rid of it. Many wearables offer a low-power mode, airplane mode, or similar settings that disable Bluetooth communication while allowing the device to continue collecting data through onboard sensors such as the accelerometer and optical heart rate sensor.</p>
<p>For people concerned about EMF exposure, this setting reduces wireless transmissions during the night while still preserving most sleep-tracking functionality on the device. The reduction in radiofrequency emissions is typically small in absolute terms because Bluetooth Low Energy already transmits at very low power and only intermittently. Still, you may prefer minimizing any unnecessary wireless activity while you sleep.</p>
<p>I’m not saying that disabling Bluetooth improves sleep quality or health outcomes. But if doing so helps you feel more comfortable or less worried about wearing a device overnight and its EMF, it can be a practical compromise that allows you to continue tracking your sleep without the added concern.</p>
<h2 id="heading-the-bigger-risk-isnt-the-radio"><strong>The Bigger Risk Isn't the Radio</strong></h2>
<p>The bigger sleep-tracking problem probably isn't EMF at all. Neurologists are seeing more patients who walk in fixated on hitting a target number of REM minutes when using a wearable device that measures sleep stages based on movement and heart rate.</p>
<p>Unlike a laboratory polysomnography test, where sleep stages are measured directly from brain activity, the measurement provided by the wearable device is only an inference based on movement and heart rate. The term used for such obsession is 'orthosomnia', which is better described as the downside of wearing a sleep tracker rather than anything related to EMFs.</p>
<p>If you're going to worry about something at 2 a.m., the accuracy of the sleep data is probably a better place to focus than the Bluetooth chip. Sleep trackers estimate sleep stages rather than measuring them directly, and that limitation can sometimes create more anxiety than the radio signals themselves.</p>
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                <title>
                    <![CDATA[ How Wearables Track the Menstrual Cycle: The Sensors, the Algorithms, and the Accuracy Gap ]]>
                </title>
                <description>
                    <![CDATA[ Your Garmin shows poor recovery, WHOOP paints your day red, your resting heart rate is high, your HRV is low, and the app recommends that you rest. But here’s the thing: you don’t actually feel bad. F ]]>
                </description>
                <link>https://www.freecodecamp.org/news/how-wearables-track-the-menstrual-cycle-the-sensors-the-algorithms-and-the-accuracy-gap/</link>
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                    <category>
                        <![CDATA[ Wearables ]]>
                    </category>
                
                    <category>
                        <![CDATA[ Health Tech  ]]>
                    </category>
                
                <dc:creator>
                    <![CDATA[ Shradha Puri ]]>
                </dc:creator>
                <pubDate>Thu, 18 Jun 2026 15:52:34 +0000</pubDate>
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                <content:encoded>
                    <![CDATA[ <p>Your Garmin shows poor recovery, WHOOP paints your day red, your resting heart rate is high, your HRV is low, and the app recommends that you rest. But here’s the thing: you don’t actually feel bad.</p>
<p>For women who are in their reproductive years, chances are your wearable technology has misread your luteal phase symptoms as either a result of being overtrained or even sick. This is because the technology likely detected a symptom that it doesn’t actually understand.</p>
<p>Let’s get into how this is actually happening by going from sensors to algorithms and finally to where the accuracy gap actually lives.</p>
<h2 id="heading-table-of-contents"><strong>Table of Contents</strong></h2>
<ul>
<li><p><a href="#heading-what-the-menstrual-cycle-actually-does-to-your-biometrics">What the Menstrual Cycle Actually Does to Your Biometrics</a></p>
<ul>
<li><p><a href="#heading-resting-heart-rate-and-hrv">Resting Heart Rate and HRV</a></p>
</li>
<li><p><a href="#heading-heart-rate-variability-hrv">Heart Rate Variability (HRV)</a></p>
</li>
<li><p><a href="#heading-skin-temperature">Skin Temperature</a></p>
</li>
</ul>
</li>
<li><p><a href="#heading-how-wearables-measure-these-signals">How Wearables Measure These Signals</a></p>
<ul>
<li><p><a href="#heading-ppg-sensors-and-what-they-actually-capture">PPG Sensors and What They Actually Capture</a></p>
</li>
<li><p><a href="#heading-temperature-sensors-continuous-vs-spot-measurement">Temperature Sensors: Continuous vs. Spot Measurement</a></p>
</li>
</ul>
</li>
<li><p><a href="#heading-how-the-algorithms-work">How the Algorithms Work</a></p>
<ul>
<li><p><a href="#heading-calendar-based-vs-physiology-based-detection">Calendar-Based vs. Physiology-Based Detection</a></p>
</li>
<li><p><a href="#heading-how-machine-learning-classifies-cycle-phases">How Machine Learning Classifies Cycle Phases</a></p>
</li>
</ul>
</li>
<li><p><a href="#heading-why-the-accuracy-gap-exists">Why the Accuracy Gap Exists</a></p>
</li>
<li><p><a href="#heading-what-cycle-aware-algorithms-look-like-in-practice">What Cycle-Aware Algorithms Look Like in Practice</a></p>
</li>
<li><p><a href="#heading-wrapping-up">Wrapping Up</a></p>
</li>
</ul>
<h2 id="heading-what-the-menstrual-cycle-actually-does-to-your-biometrics"><strong>What the Menstrual Cycle Actually Does to Your Biometrics</strong></h2>
<p>Before jumping into the sensors and algorithms, here's what they're actually detecting. The menstrual cycle isn't the noise within wearable data, but an active component that alters the physiology upon which any recovery or health algorithm relies.</p>
<p>There are three signals that tell the story.</p>
<h3 id="heading-resting-heart-rate">Resting Heart Rate</h3>
<p><a href="https://pmc.ncbi.nlm.nih.gov/articles/PMC9005074/">Multiple studies</a> using continuous wearable monitoring have confirmed that resting heart rate increases 2-7 bpm from the follicular phase to the luteal phase. One prospective study of 91 women observed that resting heart rate was 3.8 bpm higher in the mid-luteal phase compared to the period of menstruation.</p>
<h3 id="heading-heart-rate-variability-hrv">Heart Rate Variability (HRV)</h3>
<p>On the other hand, HRV changes in the opposite direction. In particular,&nbsp; <a href="https://pmc.ncbi.nlm.nih.gov/articles/PMC6912442/">a meta-analysis</a> of more than 1,000 participants showed the reduction of vagally mediated HRV from follicular to luteal phases of the menstrual cycle.</p>
<p>For example, <a href="https://pmc.ncbi.nlm.nih.gov/articles/PMC5588411/">one study reported</a> that SDNN decreased from 154 ms in the follicular phase to 136 ms in the luteal phase, which represents a decrease of 12%. Progesterone is responsible for such effects. Specifically, it triggers the renin-angiotensin system (RAS), increases the total blood volume, raises HRj, and reduces parasympathetic influence. On the other hand, estrogen decreases HR (negative chronotropic effect) and leads to greater HRV.</p>
<p>So during the mid-luteal phase, you already have an increased RHR but a reduced HRV. To a recovery algorithm that does not know where you are within your menstrual cycle, this combination signifies stress, sickness or overtraining.</p>
<h3 id="heading-skin-temperature">Skin Temperature</h3>
<p>The temperature shift has been most thoroughly studied out of the three. <a href="https://pubmed.ncbi.nlm.nih.gov/33123618/">Postovulatory rise of basal body temperature</a> by 0.3–0.7°C due to progesterone’s effect has been known for over 100 years and constitutes the basis of traditional fertility awareness methods.</p>
<p>My Oura Ring data also shows that skin temperature usually increases during the luteal phase. It also tends to drop briefly just prior to ovulation due to an abrupt drop in body temperature related to estrogen.</p>
<p>The key point here is that signals change in the same direction at the same time, every cycle, predictably. When an algorithm treats these indicators separately, it's structurally wrong.</p>
<h2 id="heading-how-wearables-measure-these-signals"><strong>How Wearables Measure These Signals</strong></h2>
<h3 id="heading-ppg-sensors-and-what-they-actually-capture">PPG Sensors and What They Actually Capture</h3>
<p>Heart rate and HRV measurements from wearables are done by Photoplethysmography (PPG). This sensor emits LED light, generally green for heart rate and red &amp; infrared for SpO2, to shine on your skin. Light gets absorbed differently by blood depending on its volume, so as your heart beats and blood flows in capillaries, light reflected from your skin will be different for each heartbeat. Variation in light reflected is known as the PPG waveform.</p>
<p>Based on PPG waveform data, wearables calculate beat-to-beat intervals. While calculating the heart rate is relatively easy as it simply counts peaks per minute, HRV needs precise timing since it measures the variation in milliseconds between consecutive heartbeats. That’s where signal quality starts to matter a lot.</p>
<p>Placement of sensors on your skin also plays a vital role in this. Generally, finger devices such as smart rings like Oura and Ultrahuman give cleaner PPG signals compared to wrist-worn devices such as your Apple Watch, Garmin, or WHOOP. The finger has higher density capillaries, resulting in larger pulse amplitude and lower motion artifacts.</p>
<p>Wristwear makes up for this problem with more sophisticated signal processing techniques. But there's always a price to pay for that. For instance, Oura Ring 4 provides users with an 18-path multilayered wavelength PPG sensor with adaptive sensor configurations.</p>
<h3 id="heading-temperature-sensors-continuous-vs-spot-measurement">Temperature Sensors: Continuous vs. Spot Measurement</h3>
<p>Temperature sensors incorporated in current wearables measure skin temperature and not core body temperature. These sensors, called thermistors, are capable of detecting temperature fluctuations in terms of changes in electrical resistance.</p>
<p>While there's a relationship between skin temperature and core body temperature, the two aren't the same. Skin temperature responds to factors such as room temperature, weather conditions, and temperature variation caused by changes in blood flow around the skin surface.</p>
<p>Even so, continuous overnight monitoring of skin temperatures may provide better information compared to traditional basal body temperature (BBT). With the fertility awareness technique, temperature is always measured at the same time each morning, right before getting out of bed. Missing a measurement or a bad night of sleep may negatively impact results.</p>
<p>Wearables take a different approach. By collecting temperature data throughout the night, they can identify longer-term trends and reduce the impact of short-term fluctuations.</p>
<p>Some devices, such as the Apple Watch Series 8 and later, Fitbit Sense, and Oura Ring, have temperature sensors. Most smart rings track temperature changes from an individual’s baseline, not the absolute temperature itself. It makes identifying temperature increases, which happen after ovulation, easier.</p>
<h2 id="heading-how-the-algorithms-work"><strong>How the Algorithms Work</strong></h2>
<h3 id="heading-calendar-based-vs-physiology-based-detection">Calendar-Based vs. Physiology-Based Detection</h3>
<p>Perhaps the most basic way of detecting the menstrual cycle is through a calendar model. The user inputs the first day of their period, the app calculates the average cycle length, and predicts the fertile window forward from there.</p>
<p>Apps like Clue, Flo, and older versions of Apple’s period tracker use this as their foundation. It’s a simple algorithm that needs no sensor data at all.</p>
<p>The problem with calendar algorithms is accuracy. These types of methods operate on regular cycles, but these aren't common in many women. For ovulation detection, for example, <a href="https://pmc.ncbi.nlm.nih.gov/articles/PMC11829181/">studies reveal</a> that there's an average error of 3.44 days for calendar methods alone.</p>
<p>Also, calendar methods predict menstrual phases based only on dates entered by the user, whereas physiology-based approaches analyze sensor data such as temperature, heart rate and HRV to detect ovulation and cycle-related changes. For example, Oura uses heart rate and temperature to detect ovulation with an average error of 1.26 days.</p>
<h3 id="heading-how-machine-learning-classifies-cycle-phases">How Machine Learning Classifies Cycle Phases</h3>
<p>Machine learning algorithms don't use a single metric to determine where you are within your menstrual cycle. Rather, they examine patterns in several physiological indicators taken from wearables, such as skin temperature, heart rate, heart rate variability (HRV), and in some cases, electrodermal activity (EDA).</p>
<p>Over time, machine learning algorithms figure out which cycle stages correspond to which physiological patterns. For example:</p>
<ul>
<li><p>The luteal stage is characterized by an increase in skin temperature and changes in cardiovascular metrics.</p>
</li>
<li><p>Ovulation causes changes in patterns in terms of temperature and heart rate.</p>
</li>
<li><p>The menstrual phase can show its own distinct combination of physiological changes.</p>
</li>
<li><p>The follicular phase is generally the most difficult one to recognize since its biometric signatures aren't clearly defined and tend to coincide with those from other phases.</p>
</li>
</ul>
<p>A <a href="https://pubmed.ncbi.nlm.nih.gov/39889448/">2025 study</a> found that machine learning algorithms can effectively determine the menstrual, ovulatory, and luteal phases. The accuracy of the results decreased when the follicular phase was added to the list of phases.</p>
<p>Modern cycle tracking apps have become complex because of this reason and they no longer depend solely on temperature. It becomes easier for a device to identify the phases of the menstrual cycle with every additional physiological signal that it captures.</p>
<p>Other technologies like the <a href="https://wearablexp.com/smart-wearables/vivoo-flowpad-smart-menstrual-pad/">Vivoo FlowPad</a> are also emerging that attempt to collect menstrual health data directly rather than inferring it from wearable sensors.</p>
<h2 id="heading-why-the-accuracy-gap-exists"><strong>Why the Accuracy Gap Exists</strong></h2>
<p>The issue with wearables comes down to the fact that many of the metrics related to menstrual cycle phases aren’t exclusive to the menstrual cycle.</p>
<p>Take, for instance, the metrics such as a high resting heart rate, reduced HRV, and increased skin temperature. These could be observed during the luteal phase, but can also occur thanks to a range of other factors, including illness, lack of sleep, stress, consumption of alcohol, or even jet lag.</p>
<p>Yet another hurdle with menstrual tracking involves individual differences since some women might have significant changes during their menstrual cycles when it comes to temperature and HRV, whereas others will have minimal changes in those metrics.</p>
<p>This is why most menstrual tracking algorithms require individual baselines instead of population baselines, meaning that the more data is collected from a woman regarding her menstrual cycles, the better it gets at identifying her personal patterns.</p>
<h2 id="heading-what-cycle-aware-algorithms-look-like-in-practice"><strong>What Cycle-Aware Algorithms Look Like in Practice</strong></h2>
<p>Until 2025, most wearables considered tracking cycles and recovery as two separate concepts. Oura became the first big company to connect the two.</p>
<p>Its updated algorithm accounts for increased resting heart rate, decreased HRV, and increased body temperature, all common during the luteal phase. Instead of automatically lowering readiness scores, it checks whether those changes are a normal part of the menstrual cycle.</p>
<p>This reduced the number of falsely low recovery scores during the second half of the menstrual cycle. In 2026, Oura went further with a dedicated AI model focused on cycles, fertility, pregnancy, and menopause.</p>
<p>WHOOP chose a different route through its metric called cardiovascular amplitude that measures heart rate and HRV variability throughout the whole cycle. Rather than focusing on individual phases, it looks at the overall physiological impact of hormonal changes.</p>
<p>Natural Cycles became the first fertility app that obtained FDA approval for contraceptive use, collecting users' body temperature data with the help of their wearables’ sensors like the Apple Watch, Oura Ring, Garmin, or its own dedicated NC Band.</p>
<p>Garmin, Fitbit, and Samsung track menstrual cycles, but those insights remain largely separate from their recovery and readiness metrics.</p>
<h2 id="heading-wrapping-up"><strong>Wrapping Up</strong></h2>
<p>This boils down to the mismatch between measurements taken by wearables and what recovery algorithms were designed to handle.</p>
<p>PPG sensors and temperature sensors allow wearables to detect changes that happen across the menstrual cycle and they work well enough. Multi-parameter machine learning allows for reliable classification of the cycle phases, particularly those happening during ovulation.</p>
<p>But problems arise because many recovery algorithms have been trained on data biased towards male samples, where hormonal cycle variations are considered to be noise. These recovery algorithms lack the means to differentiate between luteal phase physiology and initial phases of an illness. Sensors won’t solve this problem, but algorithmic design will.</p>
<p>From the perspective of developing health apps using wearable device APIs, we already have access to health metrics that incorporate information about the current stage of the cycle. Oura provides it in specific endpoints, Apple integrates with HealthKit’s HKCategoryTypeIdentifier, and WHOOP ties it into its recovery model.</p>
<p>The problem here is that data can be accessed on these platforms via different APIs, data models, and integration techniques. While Oura, Apple HealthKit, and WHOOP may expose similar health metrics, there can still be differences in the sampling frequency, preprocessing methods, and metric definitions, making it hard to create algorithms that would work consistently across platforms.</p>
<p>This lack of standardization also contributes to the training data problem. Data collected by Oura, Apple Watch, and WHOOP can't always be combined easily since each platform stores and works with data differently. As a result, researchers and developers have to do additional work preparing and normalizing data before it can be used to train models.</p>
<p>There are sensors and the models have been improving, but the APIs are fragmented and the lack of training data is real. That’s where the work is.</p>
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                <title>
                    <![CDATA[ What the new Apple Watch’s EKG means for the future of consumer wearables and healthcare ]]>
                </title>
                <description>
                    <![CDATA[ By James Hsu When Apple announced this September that its newest Series 4 Apple Watch includes EKG functionality, I imagined millions of hearts worldwide fluttering with delight. The news was significant for several reasons. The chief reason is it is... ]]>
                </description>
                <link>https://www.freecodecamp.org/news/what-the-apple-watchs-new-ekg-feature-means-for-the-future-of-consumer-wearables-and-medicine-4189c070a4e/</link>
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                <pubDate>Wed, 24 Oct 2018 17:47:19 +0000</pubDate>
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                    <![CDATA[ <p>By James Hsu</p>
<p>When Apple announced this September that its newest Series 4 Apple Watch includes EKG functionality, I imagined millions of hearts worldwide fluttering with delight.</p>
<p>The news was significant for several reasons. The chief reason is it is the first time a mainstream consumer wearable device will perform a sophisticated medical procedure. This same procedure we need to see the doctor for today.</p>
<p>To understand the significance, you need first to set aside the fact that health and fitness are already key reasons why consumers currently use wearables. Fitness trackers have had <em>heart rate</em> sensors for many years now.</p>
<p>(Heart rate sensors are convenient for fitness purposes, to be sure. But, they’re also primitive. Anyone with a finger can feel for a pulse and calculate a heart rate if necessary.)</p>
<p>An <a target="_blank" href="https://www.webmd.com/heart-disease/electrocardiogram-ekgs#1">EKG (or ECG/electrocardiogram)</a> is different than a heart rate measurement. For one, because an EKG looks at the heart’s electrical impulses to monitor for and identify specific heart anomalies. These anomalies are the immediate precursor to serious medical conditions. Conditions like strokes or heart attacks.</p>
<p><em>The technology can and will save lives.</em></p>
<p>By adding new and substantial medical features, Apple (and others) could be paving the way to a future in which wearables serve as the frontline for the diagnosis, treatment, and even prevention of serious medical conditions.</p>
<p><img src="https://cdn-media-1.freecodecamp.org/images/0*pexRirzLZVNNWU8t.jpg" alt="Image" width="800" height="456" loading="lazy">
<em>Hold your finger on the crown of the Series 4 Apple Watch, and you’ll get an EKG reading on the spot.</em></p>
<h3 id="heading-the-apple-watch-is-a-class-ii-medical-device">The Apple Watch is a class II medical device.</h3>
<p>Adding an EKG to the Apple Watch wasn’t just an engineering task.</p>
<p>It also required the attention and cooperation of the notoriously finicky Food and Drug Administration (FDA). The FD has cleared Apple’s use of two medical-grade features in the new Apple Watch: 1) the EKG, and 2) the Apple Watch’s ability to identify and notify users of an irregular heart rhythm.</p>
<p>It’s important to note that, with the FDA, “clearing” a device is not the same as “approving” one. The latter is much harder to do and requires much significant collaboration and testing to mitigate potential risks. Clearing the Apple watch took just one month from application to decision. Class II devices like the new Apple Watch don’t require FDA approval because the associated health risks aren’t deemed great enough to warrant a more rigorous vetting process.</p>
<p>It’s also important to understand that <a target="_blank" href="https://www.accessdata.fda.gov/cdrh_docs/pdf18/DEN180044.pdf">the FDA clearance letters</a> came with language stating that the cleared features are not intended for users under the age of 22, and are “not intended to replace traditional methods of diagnosis or treatment.”</p>
<p>Regarding the latter, what this means is that after your Apple Watch tells you it has detected a mild heart arrhythmia, you’ll probably want to follow up with your doctor to get a proper diagnosis.</p>
<p>On the other hand, if your Apple Watch tells you you’ve just had a heart attack, immediate urgency (and common sense) dictates that you’re going to go straight to the ER or call an ambulance, skipping the “traditional method of diagnosis” referenced in the FDA’s letter.</p>
<h3 id="heading-a-beachhead-for-new-medical-functionality">A beachhead for new medical functionality</h3>
<p>With the regulatory precedent established, Apple product managers are undoubtedly considering more medical functionality, to double down on this growing notion of the Apple Watch as a medical device.</p>
<p>If so, what might we see from Apple down the road?</p>
<p>Well, as it turns out, Apple has for <a target="_blank" href="https://www.theverge.com/2017/5/19/15662316/apple-watch-glucose-tracker-tim-cook">years been working on developing a blood glucose tracker</a> that ties to the Apple Watch. Such a tracker could help with diagnosis, treatment, and perhaps even prevention of type 2 diabetes.</p>
<p>Diabetes currently affects an estimated 30 million people in the United States alone. The challenge has been creating <em>noninvasive</em> technology that doesn’t require permeating the skin you to get a reading, as current glucose trackers must do. According to a CNBC report last year, Apple has assembled a new team to pursue this “holy grail” breakthrough.</p>
<p>Here’s Apple CEO Tim Cook on the opportunity with glucose trackers:</p>
<blockquote>
<p>“It’s mentally anguishing to stick yourself many times a day to check your blood sugar. There is lots of hope out there that if someone has constant knowledge of what they’re eating, they can instantly know what causes the response… and that they can adjust well before they become diabetic.”</p>
</blockquote>
<p><img src="https://cdn-media-1.freecodecamp.org/images/0*AHq3637kPWpZJ8nd.jpg" alt="Image" width="800" height="533" loading="lazy">
<em>Apple CEO Tim Cook appears to be gung-ho about enabling the Apple Watch as a medical device, with CNBC reporting last year that he was personally testing a blood glucose tracker for the Apple Watch.</em></p>
<h3 id="heading-impact-on-healthcare-practices-and-insurance-costs">Impact on healthcare practices and insurance costs</h3>
<p>Cook’s predecessor, the legendary visionary Steve Jobs, reportedly first envisioned the popularization of consumer wearables that could provide blood glucose readings and other health vitals.</p>
<p>If Jobs’ vision of a versatile wearable health tracker comes to fruition, what effect might this have on the time-tested practice of the “annual physical?” For one, we might very well see formal doctor checkups give way to daily or even hourly automated testing through wearables like the Apple Watch.</p>
<p>And if this happens, what implication might widespread use of the device have beyond users’ health, for instance, on healthcare costs and the healthcare system itself? North American healthcare provider United Healthcare is an example of one insurance provider that is already <a target="_blank" href="https://www.uhc.com/employer/programs-tools/for-employees/unitedhealthcare-motion">offering financial incentives to customers that use wearable fitness trackers to meet daily fitness goals</a>.</p>
<p>When customers get ahold of devices that also address the medical component of wellness and longevity, I’d certainly expect to see such financial incentives increase and healthcare premiums decrease.</p>
<h3 id="heading-wearable-medical-technology-is-not-a-one-horse-race">Wearable medical technology is not a one-horse race</h3>
<p>FitBit, the other big player in health and fitness wearables, <a target="_blank" href="https://www.wired.com/story/when-your-activity-tracker-becomes-a-personal-medical-device/">has had a blood oxygen sensor built into its Ionic watch for more than a year</a>. The sensor can be used to detect common breathing related disorders such as asthma, sleep apnea, and even heart arrhythmia conditions such as atrial fibrillation.</p>
<p>There’s a problem, though. At the time of this story’s publication, Fitbit has not yet publicly released software that makes use of the hardware sensor.</p>
<p>Samsung is another company that has demonstrated a commitment to adapting its wearable technologies to support medical use cases.</p>
<p>For instance, Samsung’s Gear VR headset is used by California-based <a target="_blank" href="https://irisvision.com/">IrisVision</a> to allow legally blind users to see clearly in all aspects of life. Using <a target="_blank" href="https://citrusbits.com/portfolio/irisvision/">custom IrisVision software</a>, the IrisVision headset uses proprietary visual acuity algorithms to amplify any remaining useful vision a user still has. The result is clear vision and, for many users, the restoration of independence in their daily lives. IrisVision has the financial support of the National Institute of Health (NIH) and was developed by leading vision experts from Johns Hopkins University, UC Berkeley, Stanford, and UCLA.</p>
<h3 id="heading-medical-wearables-will-empower-clinical-researchers">Medical wearables will empower clinical researchers</h3>
<p>Beyond consumer healthcare, clinical researchers stand to benefit from these recent developments in wearables, too. When doing any sort of clinical research, getting reliable data can be an enormous challenge, especially when a study depends on self-reported data or recollections.</p>
<p>Even for clinical studies that do use lab results, gathering data collection can be a challenge — costly, impractical, or even impossible.</p>
<p><img src="https://cdn-media-1.freecodecamp.org/images/0*Oq8V1mawbYvZH8ZL.jpg" alt="Image" width="800" height="532" loading="lazy">
<em>In clinical testing and research, data collection can be a considerable challenge without sophisticated wearables.</em></p>
<p>But, if these measurements can be taken automatically by a wearable device, that largely addresses the issue, providing rich, reliable, and (perhaps) actionable data to researchers whose work depends on the availability of data they can trust.</p>
<p>Case in point, Johns Hopkins University has for the past three years <a target="_blank" href="https://www.hopkinsmedicine.org/epiwatch/#.W8e46GhKiUk">been conducting a clinical study that allows participants to use their Apple Watches and the university’s EpiWatch app</a> to provide clinical data (heart rate and accelerometer data) to further their understanding of epilepsy.</p>
<p>And, just last September, the NIH granted $2.5M to <a target="_blank" href="http://www.biosensics.com/">BioSensics</a> to develop wearable sensors to monitor the symptoms of Huntington’s disease. <a target="_blank" href="https://clinicaltrials.gov/ct2/show/NCT03599076">A pilot study in collaboration with The University of Rochester is now underway</a>.</p>
<h3 id="heading-wearables-provide-the-sensors-and-hardware-but-user-experience-is-paramount">Wearables provide the sensors and hardware, but user experience is paramount.</h3>
<p>The hardware engineering associated with integrating medical sensors into small wearables is just one aspect of the challenge.</p>
<p>Another aspect of the challenge is inventing non-invasive or otherwise “user-friendly” sensors that can provide readings equivalent to what we, for example, currently need to draw blood to obtain. Frankly speaking, consumers will not buy a device that causes them pain or even startles them on a regular basis.</p>
<p>The regulatory hurdles (à la FDA) are another aspect of challenge, albeit one that seems promising based on the recent Apple clearances.</p>
<p>The final challenge is the software and user experience, which bring meaning to the data collected by the sensors. Sure, you can have an EKG provide readings — a line graph of electrical impulses — but how do you deliver that to your end user in a way that is not just useful, but is also intuitive and even enjoyable?</p>
<p>According to <a target="_blank" href="https://citrusbits.com/">CitrusBits</a> CEO, Harry Lee, apps are often the biggest competitive differentiator for wearables companies.</p>
<blockquote>
<p>“In the wearables space, the hardware aspect is already somewhat commoditized. Everyone, more or less, has access to the same sensors, microprocessors, and chips. Where companies like Apple, Fitbit, and CitrusBits stand apart is in their ability to design intuitive and robust apps for smartwatches and other devices, given inherent screen-size and control constraints. This is absolutely key to adoption, and we’ve already seen once-promising wearables companies such as Pebble forced to shut down in recent years, in part due to weak app offerings.”</p>
</blockquote>
<p>Looking ahead, the realization of Steve Jobs’ vision is clearly upon us: a future in which medical wearables will play a big role, perhaps even reducing the strain on existing healthcare systems.</p>
<p>It just may very well depend on a harmonious blend of computing hardware, non-invasive medical sensors, progressive regulatory oversight, and thoughtfully-crafted applications.</p>
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