# HRV4Training vs Rhythm SYNC.

The clearest difference is review sentiment: HRV4Training at 61% against Rhythm SYNC.'s 13%. HRV4Training also leads on rating (3.6 vs 1.8) and chart position (#9 vs unranked). Rhythm SYNC.'s advantage is price (Free vs $9.99) and iOS requirement (12.0 vs 15.6). On ratings volume, update cadence, ads and in-app purchases there is nothing between them.

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

HRV4Training holds the better App Store score, 3.6 against 1.8. Both are backed by a comparable volume of ratings — 288 and 128 respectively. Written reviews point the same way: 61% of HRV4Training's written reviews are positive against 13% of Rhythm SYNC.'s.

HRV4Training ships an update every 6 weeks, Rhythm SYNC. every 3 months. The most recent releases landed on September 24, 2026 and September 3, 2026 respectively.

## The numbers

| Metric | HRV4Training | Rhythm SYNC. |
| --- | --- | --- |
| Price | $9.99 | **Free** |
| Rating | **[3.6 (288 ratings)](https://appshunter.io/ios/app/hrv4training/id686923970/reviews)** | [1.8 (128 ratings)](https://appshunter.io/ios/app/rhythm-sync/id1226606963/reviews) |
| Number of ratings | **288** | 128 |
| Positive reviews | **61.2% of reviews** | 13.1% of reviews |
| In-app purchases | No | No |
| Ads | No | No |
| Update frequency | **Every 6 weeks** | Every 3 months |
| Monetization | Paid | **Free** |
| Best chart rank | **#9** | — |
| Size | 35 MB | 47 MB |
| Requires iOS | 15.6 | **12.0** |
| Devices | iPhone, iPod | iPhone, iPod |
| Age rating | 4+ | 4+ |
| Developer | [A.S.M.A. B.V.](https://appshunter.io/developer/1066843463) | [Scosche](https://appshunter.io/developer/340018842) |

## What reviewers say

### HRV4Training

[App page](https://appshunter.io/ios/app/hrv4training/id686923970)

**Currently charting:** #9 Top Paid · Health & Fitness (US App Store)

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:** Vision Pro support

**In-app purchases:** none

**What reviewers like**

- 👍 Accurate HRV measurements
- 🚀 Straightforward and easy to use
- 💡 Provides valuable insights for training and recovery
- 👍 Integrates well with other fitness apps
- 👍 Responsive and helpful developer support

**What reviewers complain about**

- 🐛 Inconsistent readings and technical issues
- 🔒 Requires user account and data sharing
- 🔒 Concerns about data privacy
- 🔋 Drains battery when using camera for measurements

**Reported bugs**

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

**Requested features**

- 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


### Rhythm SYNC.

[App page](https://appshunter.io/ios/app/rhythm-sync/id1226606963)

This app connects to heart rate monitors to display real-time data, manage activity modes, and track workout history. It allows for software updates and integrates with HealthKit for saving workout data.

**Highlights:** Connects to Rhythm 24 and Rhythm+ monitors, Manages activity modes and biometrics, Displays heart rate and battery level, Configures data sharing with other apps, Collects and downloads recorded activities, Performs software and firmware updates, HealthKit integration

**In-app purchases:** none

**What reviewers like**

- ✅ Accurate heart rate readings
- 🔋 Long-lasting device battery life
- 🔄 Reliable device hardware
- 📱 Simple and straightforward interface
- 🔗 Works well with third-party apps (Peloton, Garmin, Apple Watch)

**What reviewers complain about**

- 🐛 Frequent Bluetooth connection failures
- 🐛 App crashes and freezes regularly
- ❌ App doesn't recognize connected devices
- ⚠️ HRV mode difficult or impossible to access
- 📊 Extremely limited app functionality

**Reported bugs**

- App fails to detect device despite Bluetooth connection
- Bluetooth connection drops frequently during workouts
- App crashes on startup (splash screen freeze)
- Firmware update fails repeatedly
- HRV readings not displaying or accessible

**Requested features**

- HRV (Heart Rate Variability) mode that actually works
- Comprehensive workout history and logging
- Data export to multiple health apps (MyFitnessPal, TrainingPeaks, etc.)
- Customizable heart rate zones that persist
- Batch download and export of multiple files


## Frequently asked questions

### Is HRV4Training free?

HRV4Training costs $9.99, with no in-app purchases.

### Is Rhythm SYNC. free?

Rhythm SYNC. is free to download, with no in-app purchases.

### Which has better reviews, HRV4Training or Rhythm SYNC.?

HRV4Training is rated higher. HRV4Training averages 3.6 out of 5 from 288 ratings, while Rhythm SYNC. averages 1.8 from 128 ratings.

### Do HRV4Training or Rhythm SYNC. have ads?

Neither HRV4Training nor Rhythm SYNC. shows ads.

### Which is updated more often, HRV4Training or Rhythm SYNC.?

HRV4Training ships an update every 6 weeks, and Rhythm SYNC. every 3 months. Most recently, HRV4Training was updated on September 24, 2026 and Rhythm SYNC. on September 3, 2026.

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*Compared by [AppsHunter](https://appshunter.io/) from daily US App Store data. Review summaries are generated from verbatim App Store reviews.*