Comparison

HRV4Training vs CORE Thermal Sensor

Price, ratings, monetisation and update history for both apps, side by side — with what reviewers say about each.

Head to head
About

HRV4Training

Quantify stress, balance training and lifestyle, and improve performance with scientifically validated heart rate variability insights. This app accurately assesses HRV using your phone's camera or compatible devices, offering actionable interpretations for optimizing your training plan.

Highlights
  • HRV-based stress quantification
  • Training and lifestyle balance
  • Performance improvement insights
  • Camera-based HRV assessment
  • Integration with wearables
  • Training load analysis
  • VO2max and Lactate Threshold estimation
Features
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The first scientifically validated Heart Rate Variability (HRV) app. HRV4Training provides HRV based insights to help you quantify stress, better balance training and lifestyle, and improve performance. HRV4Training does not require a heart rate monitor, since it can accurately assess your HRV using the phone's camera. HRV4Training also works with Apple Watch, the Oura ring and all compatible Bluetooth SMART sensors. HRV4Training is also the first app that goes beyond simple measurements and provides insights on: 1) acute or day to day HRV changes in response to different stressors (alcohol, travel, sick days, training, menstruation, etc.) 2) long term multi-parameter trends to look at the big picture 3) correlations between physiological measurements and annotations 4) training load analysis, fitness, fatigue, readiness to perform and injury risk 5) VO2max estimation for runners linking the app to Strava or TrainingPeaks and using a heart rate monitor during their workouts 6) Training Polarization analysis (or 80/20) 7) Lactate Threshold Estimation for runners linking the app to Strava or TrainingPeaks and using a heart rate monitor during their workouts 8) Weekly and monthly summaries to track progress. All data is processed inside the app in order to provide you with actionable interpretations that can help optimizing your training plan and performance. Supported devices for the camera measurement: iPhones 5, 5S, 6, 6S, 6+, 6S+, SE, 7, 7+, 8, 8+, X, XS, XS Max, XR, 11, 11 Pro, 11 Pro Max, 12 mini, 12, 12 Pro, 12 Pro Max, 13 mini, 13, 13 Pro, 13 Pro Max, 14, 14 Plus, 14 Max, 14 Pro, 15, 15 Max, 15 Pro, 16, 16 Max, 16 Pro Currently unsupported devices for the camera measurement: iPhones 4S, iPads and iPods - These devices require a chest strap. Other features: - HRV-based advice helps you to adapt your trainings based on objective measures of recovery - TAGS: lets you tag your sleep, mental energy, muscle fatigue, stress and all other parameters that can help you understand what is influencing your physical condition and physiological stress - Works with Bluetooth SMART heart rate monitors (a Polar H7 is recommended) or simply your phone's Camera - Integrates with the Health app (writes heart rate, and sleep, read sleep time) - Configurable test (single or orthostatic, choose test duration between 1, 3 or 5 minutes) - Extracts and stores the following features while lying down and/or standing: heart rate, mean of beat-to-beat intervals (AVNN), standard deviation of beat-to-beat intervals (SDNN), square root of the mean squared difference of successive R-Rs (rMSSD), number of pairs of successive R-Rs that differ by more than 50 ms (pNN50), low frequency power (LF, 0.04-0.15 Hz), high frequency power (HF, 0.15-0.40 Hz) - Shows the PPG signal view to ensure signal quality during the test if the camera is used instead of a bluetooth SMART sensor - HRV4T Recovery Points to provide a single, straightforward metric to analyze your physical condition - Population summaries and people like you comparisons to put your data into perspective - Analysis of compliance and consistency - Data export via email or Dropbox - Integrates with TrainingPeaks, Oura, Strava and Coros HRV4Training requires to register an account with your email address, so that your data can be backed up safely and retrieved in case anything happens (app issue, changing phone, etc.). HRV4Training does not provide medical advice. It is intended for informational purposes only. Consult a medical professional before making health or lifestyle decisions. Please find an overview of the relevant scientific literature in our guide, here: https://marcoaltini.substack.com/p/the-ultimate-guide-to-heart-rate

About

CORE Thermal Sensor

This app continuously monitors your core body temperature and thermal strain, providing critical data for heat training and optimal race performance. It helps athletes of all levels improve their training and achieve better results.

Highlights
  • Continuous core body temperature monitoring
  • Real-time Heat Strain Index
  • Heat Zones for training and racing
  • Heat Training Load and Adaptation Score
  • Passive heat training tracking
  • Data trends and historical analysis
  • Connectivity with sports devices
Features
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The CORE Thermal Sensor accurately measures your core body temperature and thermal strain on your body – continuously and non-invasively. Thermal data and insights are critical for facilitating safe and effective heat training and for performing optimally on race day. Designed for athletes at all levels, CORE will help to improve your training and performance in your personal adventures or races. IMPORTANT: The CORE app is designed to work with the CORE device which you can order at www.corebodytemp.com Here's how it works: • Set up your CORE sensor: connect your heart rate monitor and sports devices for optimal sensor use. • Measure your thermal vitals during training: mount the newly designed clip on your heart rate strap and snap in the CORE sensor. Shake the sensor to wake it up, wear it and track your thermal data. • Core body temperature: the interior temperature deep in your body, including organs and other tissues. A critical measure during sports, it can reach up to 40°C (104°F) during vigorous activity in hot environments. Be aware that hotter is not better – cooler is faster. • Heat Strain Index: A combination of your core body temperature and skin temperature representing the thermal strain on your body. The real-time feedback on how hard your body is working to stay cool, delivering a value from 0 (no heat strain) to around 10 (extremely high heat strain). • Heat Zones: Your Heat Strain Index divided into easy-to-use zones. Heat Zone 3 will likely lead to a performance loss, BUT it is the needed stimuli to create adaptations in your body. During heat training, strive for time in heat zone 3. During racing, stay cool and prevent a performance loss by staying in heat zone 1 or 2. • Heat Training Load: a cumulative daily metric of the heat strain on your body. A daily value of 10 out of 10 indicates ideal contribution to heat adaptations. More is not always better! • Heat Adaptation Score: Track your heat adaptations over time with effective heat training. Get a heat champion to perform best in the heat. Long-term heat training will most likely lead to improvements also in cool conditions. • Add your passive heat training: Supplementing your active heat training or general training with passive heat exposure in a sauna or hot bath. You can track your sessions in the app manually, contributing to your heat adaptation score. NOTE: do NOT take your CORE sensor into the sauna or hot environments. What else you can do in the CORE app: • Dig into the details: See a breakdown of your thermal data, and even see trends across days, weeks and months. • Share your CORE metrics with your friends through the social sharing feature, earning more kudos and likes • Connect your connectivity accounts (e.g. Garmin) to directly synchronize your data after the training. • Update your sensor to the latest firmware ensuring having the best sensor functionality. Note: CORE provides products and services designed for general fitness and training purposes. For accurate measurement readings during sports, a connection to a heart rate monitor is necessary. CORE products and services are not medical devices, not intended to treat or diagnose any disease, and should not be used as a substitute for professional medical advice, diagnosis or treatment. All content available through CORE products and services is for general informational purposes only.

Screenshots

HRV4Training4 screens
CORE Thermal Sensor4 screens

Verdict

The call

The clearest difference is review sentiment: HRV4Training at 61% against CORE Thermal Sensor's 16%. HRV4Training also leads on rating (3.6 vs 2.5) and chart position (#40 vs unranked). CORE Thermal Sensor's advantage is price (Free vs $9.99). On update cadence, ads, in-app purchases and device support there is nothing between them.

Scored on Price · Rating · Positive reviews · Number of ratings · Update frequency · Ads · In-app purchases · Monetization · Best chart rank · Devices · Requires iOS

CostPrice · In-app purchases · Ads · Monetization

CORE Thermal Sensor is free to download; HRV4Training costs $9.99 up front. Neither carries in-app purchases, so what you see is what you pay.

ReceptionRating · Positive reviews · Number of ratings

HRV4Training holds the better App Store score, 3.6 against 2.5. That said, the two scores are not equally well evidenced: HRV4Training has 288 ratings behind it against 35, so its average is the more settled of the two. Written reviews point the same way: 61% of HRV4Training's written reviews are positive against 16% of CORE Thermal Sensor's.

UpkeepUpdate frequency

HRV4Training ships an update every 6 weeks, CORE Thermal Sensor every 2 months. The most recent releases landed on October 13, 2026 and October 6, 2026 respectively.

Scorecard6 real differences · 5 level
HRV4Training versus CORE Thermal Sensor: the parameters behind the verdict, then further details
ParameterHRV4TrainingCORE Thermal Sensor
Price$9.99Free — better
Rating3.6 (288 ratings) — better2.5 (35 ratings)
Positive reviews61.2% of reviews — better15.6% of reviews
Number of ratings288 — better35
Update frequencyEvery 6 weeks — betterEvery 2 months
AdsNoNo
In-app purchasesNoNo
MonetizationPaidFree — better
Best chart rank#40 — better—
DevicesiPhone, iPodiPhone, iPad, iPod — better
Requires iOS15.615.1 — better
Further details — not scored
Size35 MB55 MB
Age rating4+4+
DeveloperA.S.M.A. B.V.greenteg AG

Customer experience

HRV4Training

All ratings288 ratings
Positive62.2%
Neutral5.6%
Negative32.3%
Written reviews451 reviews
Positive61.2%
Neutral7.3%
Negative31.5%

CORE Thermal Sensor

All ratings35 ratings
Positive22.9%
Neutral20.0%
Negative57.1%
Written reviews32 reviews
Positive15.6%
Neutral25.0%
Negative59.4%

Bugs and requests

HRV4Training

Reported bugs

3 issues
  • App crashes frequently, especially with iOS updates
  • Syncing issues with Strava, TrainingPeaks, and Apple Health
  • Camera-based measurements often unreliable or inconsistent

Requested features

4 requests
  • Allow multiple measurements per day
  • Improve integration with Apple Watch and other wearables
  • Add more customization options and data visualization
  • Expand support for non-athletic use cases

CORE Thermal Sensor

Not enough reviews yet to summarise bugs or requests.

In-app purchases

None

HRV4Training

No in-app purchases

None

CORE Thermal Sensor

No in-app purchases

Questions

Is HRV4Training free?
HRV4Training costs $9.99, with no in-app purchases.
Is CORE Thermal Sensor free?
CORE Thermal Sensor is free to download, with no in-app purchases.
Which has better reviews, HRV4Training or CORE Thermal Sensor?
HRV4Training is rated higher. HRV4Training averages 3.6 out of 5 from 288 ratings, while CORE Thermal Sensor averages 2.5 from 35 ratings.
Do HRV4Training or CORE Thermal Sensor have ads?
Neither HRV4Training nor CORE Thermal Sensor shows ads.
Which is updated more often, HRV4Training or CORE Thermal Sensor?
HRV4Training ships an update every 6 weeks, and CORE Thermal Sensor every 2 months. Most recently, HRV4Training was updated on October 13, 2026 and CORE Thermal Sensor on October 6, 2026.

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