# Zx: Heart Rate Zones Training — Interval Timer & HIIT Trainer > Heart rate zone interval timer and HIIT trainer with custom and community workouts. (iPhone/iPad app by OverSphere LLC.) - Source: https://appshunter.io/ios/app/zx-heart-rate-zones-training/id1457355997 (this page in markdown: same URL + `.md`) - Developer: [OverSphere LLC](https://appshunter.io/developer/1181584266) - Category: Health & Fitness, Lifestyle - Price: Free with in-app purchases - Rating: 4.30/5 from 70 App Store ratings · 21 written reviews indexed - Age rating: 4+ - Requires: iOS 18.0 · 51 MB - Languages: American English, Dutch, French (France), German (Germany), Italian, Japanese, Korean, Brazilian Portuguese, Chinese (Simplified, China), Latin American Spanish - Released: 2019-12-22 - Data updated: 2026-08-05 - Monetization: subscription - User reviews in markdown: https://appshunter.io/ios/app/zx-heart-rate-zones-training/id1457355997/reviews.md ## What is Zx? Zx is your personal heart rate coach designed to guide you through your interval training. Create your own interval workouts or download workouts created by the community. Official Zx workouts are updated regularly. Zx supports Apple Watch or any compatible stand alone bluetooth heart rate monitor. ◎ Benefits of HIIT: - Weight loss - Improve your body’s ability to burn fat - Increase your anaerobic threshold - Improve your vo2Max - Improve performance in sports - Feel better by releasing beta-endorphins - More fun then steady state training! ◎ Integrates with the Health app to gain deep insight into your training: - View relevant Heart Rate and Workout stats for Day, Week, and Month on the home screen - See which zone your workout heart rate has spent the most time in to help you plan your next workout. ——————-—- App Features ———————— ◎Open Mode (Apple Watch only): - Not up for a guided session? Open session lets you see what Zone you’re in and how long you’ve been in it. ◎ Guided Interval Training - Zx will help you stay in a specific zone for the right amount of time. ◎ Create custom workouts - Studio lets you create custom guided training suited to your personal goals ◎ Download workouts created by other users - See what other users have created, download and remix. Health Disclaimer: Zx cannot treat or diagnose any medical condition. Zx is designed to push you to your maximum heart rate; while there shouldn’t be cause for concern with healthy individuals, always consult with your physician prior to starting any training regimen. Subscription Terms: Your subscription automatically renews every month or year unless auto-renewal is turned off at least 24 hours before the end of the current subscription. 3 day free trial is provided for monthly subscriptions. You will be charged starting at $2.99 per month, depending on the subscription pack. Your account will be charged for a renewed subscription within 24 hours prior to the end of current subscription. You can manage your subscription and switch off the auto-renewal by accessing your iTunes account settings after purchase. You cannot cancel the current subscription during the active subscription period. Any unused part or time-span of a free trial period will be forfeited, as soon as you purchase a subscription. Buy subscribing, you affirm your agreement to our Terms of Use and Privacy Policy. Terms of Use: https://www.oversphere.net/terms-of-use/ Privacy Policy: https://www.oversphere.net/privacy-policy/ ## Key features - Heart rate zone coaching - Custom interval workout creation - Community workout library - Guided interval training - Open mode for real-time zone tracking - Health app integration ## Pricing and in-app purchases Base price: Free. **Subscriptions** | Subscription | Price | Period | | --- | --- | --- | | Premium Monthly | $2.99 | per month | | Premium Yearly | $24.99 | per year | | Premium 6 months | $9.99 | per 6 months | | Premium Monthly | $0.99 | per month | | Premium 6 months | $7.99 | per 6 months | **One-time purchases** | Purchase | Price | Type | | --- | --- | --- | | Premium Lifetime Access | $14.99 | one-time | ## Recent user reviews (10 of 21) All indexed reviews: https://appshunter.io/ios/app/zx-heart-rate-zones-training/id1457355997/reviews.md ### 5/5 — What I wanted *2025-08-03, version 1.7* Does what it says but please let us choose the language (in the app and on the watch). The German translation is confusingly wrong. ### 5/5 — Great workout companion! *2024-09-23, version 1.7* Really helpful for taking a look at hr data ### 5/5 — Fantastic app! *2024-09-13, version 1.6.1* I was looking for an interval timer for my own HIIT training that could also pair with my coros armband to show my heart rate. Paying $14 for this app seemed like a no-brainer when the cheapest watch I could find to show my heart rate was $180. Now I get to see my interval timer and heart rate in the one place. It works perfectly with my coros armband and make sure I stay in the zone during night intensity intervals (while not pushing too hard above my range). Thanks for making such an intuitive and affordable app with great functionality. ### 1/5 — Custom and community workouts not showing on my watch *2024-06-26, version 1.5* I’m not able to use the custom and community workouts after paying for this app because they don’t show up on my watch. 😕 ### 4/5 — Good simple interface-some iwatch sync issues *2024-03-01* Love the clear interface on the app. Can’t seem to sync studio and community workouts to my iwatch however. **Developer response:** Hello Bents76! Thanks for using Zx! We are aware of sync issues users are having and it not being as fast as it used to be. It may take awhile but workouts should eventually sync to your Watch. We are working on that and hopefully we can get a fix out soon. If you have any other issues or feature requests, please don't hesitate to reach out to support@oversphere.net. Best, Jillian OverSphere Support ### 4/5 — Swimming doesn't work *2023-12-13, version 1.5* App is promising. While running and cycling work fine, logging a swimming workout fails. It says "Please allow Zx to 'Write Workout Data' in Health and try again. By the way your support website is just a placeholder site. Might want to update that. In addition to the above bug, to be useful during swimming, the alerts would have to be different patterns for above and below zone, and they'd have to be constant. For example, short quick vibrations if below zone and long slow vibrates if above zone. The same kind of constant and differentiated alerts would be useful in other situations (e.g. watch under your sleeve or glove) but especially in swimming when it's not practical to look at the watch face during a lap. ### 1/5 — Eh *2023-10-20, version 1.5* I got this app thinking it would give me realtime workout info on what zone I am in and for how many minutes. It’s just like all the other apps. you can only see what zone you are in at that exact moment. It’s not realtime info (the kind you can use to guide your workout ### 1/5 — Rip off *2023-07-20, version 1.5* I was looking for something to exactly what this app should do, if it worked! But the studio (self-created) workouts don’t work! They don’t sync with your phone and when you open it on your watch it just spins.. waiting for you to start the workout (that does not appear) on your watch. Biggest waste of $15. I tried to contact support but my email was bounced back and the link from the App Store leads to a page that says coming soon. I’m going to try to request a refund because this is so pointless. A shame because I would have gladly paid the $15 for something that worked as expected. ### 2/5 — Support did not respond *2023-06-07, version 1.5* I contacted support about the zone categories double the amount of time I worked out in each zone. I sent a screen shot showing that I worked out 6 minutes in the intensity zone according to my custom heart rate and it recorded over 12 minutes. I requested help and the answer was “crickets”…I’ve been totally ghosted. I would have rated the app a 4 star, otherwise. ### 5/5 — Apps doesn’t work right *2022-10-30, version 1.4.12* It worked at first but no longer sync with Apple Watch ## Frequently asked questions about Zx ### What does Zx: Heart Rate Zones Training do? This app serves as a personal heart rate coach for interval training. It helps you create or download workouts, guiding you to stay within specific heart rate zones during your HIIT sessions. It also integrates with health apps to provide detailed insights into your training performance. ### What are the key features of this app? Key features include guided interval training that helps you maintain target heart rate zones, the ability to create custom workouts, and access to a library of workouts created by the community. It also offers an 'Open Mode' for real-time zone tracking and integrates with the Health app for comprehensive data analysis. ### How much does Zx: Heart Rate Zones Training cost? The app operates on a subscription model with a 3-day free trial for monthly subscriptions. Subscriptions start at $2.99 per month and automatically renew unless turned off at least 24 hours before the current subscription ends. Pricing may vary based on the subscription pack chosen. ### What devices is this app compatible with? The app supports Apple Watch for its 'Open Mode' and can be used with any compatible standalone Bluetooth heart rate monitor. It also integrates with the Health app on iOS devices to provide deeper insights into your training data. ### Who would benefit from using this app? This app is ideal for fitness enthusiasts who engage in interval training or HIIT workouts and want to optimize their performance by training within specific heart rate zones. It's also beneficial for those looking to improve weight loss, fat burning, anaerobic threshold, and overall sports performance. ## Version history (last 5 releases) ### 1.8.1 — 2026-07-18 - Fixed a Studio issue preventing small intervals from being added to custom workouts. ### 1.8 — 2026-01-10 - Updated localization for German, French, Spanish, and Japanese - Added "Report Translation Issue" to Settings ### 1.7 — 2024-09-19 - GOOOOOOOOOOOAAAALLLL! Add and track time spent in your target zone with this new feature. - Fixed an issue where created and downloaded workouts would take a long time to sync to the Watch app. - various bug fixes ### 1.6.1 — 2024-08-09 - GOOOOOOOOOOOAAAALLLL! Add and track time spent in your target zone with this new feature. - Fixed an issue where created and downloaded workouts would take a long time to sync to the Watch app. - various bug fixes ### 1.6 — 2024-08-08 - GOOOOOOOOOOOAAAALLLL! Add and track time spent in your target zone with this new feature. - Fixed an issue where created and downloaded workouts would take a long time to sync to the Watch app. - various bug fixes ## Apps similar to Zx | App | Rating | Price | Category | | --- | --- | --- | --- | | [Zone 2: Heart Rate Training](https://appshunter.io/ios/app/zone-2-heart-rate-training/id6444690892) | 4.7 (237) | Free | Health & Fitness | | [Interval Timer - Tabata Timer](https://appshunter.io/ios/app/interval-timer-tabata-timer/id406473568) | 4.5 (18,999) | Free | Health & Fitness | | [Intervals Pro: HIIT Timer](https://appshunter.io/ios/app/intervals-pro-hiit-timer/id957586938) | 4.8 (13,511) | Free | Health & Fitness | | [Workout Timer Custom Intervals](https://appshunter.io/ios/app/workout-timer-custom-intervals/id1669997130) | 4.5 (137) | Free | Health & Fitness | | [Interval Timer □ HIIT Timer](https://appshunter.io/ios/app/interval-timer-hiit-timer/id1124297113) | 4.8 (85,576) | Free | Health & Fitness | | [C25K® 5K Running Coach & Map](https://appshunter.io/ios/app/c25k-5k-running-coach-and-map/id485971733) | 4.8 (170,348) | Free | Health & Fitness | ## More apps by OverSphere LLC - [mileMate: Mileage Tracker](https://appshunter.io/ios/app/milemate-mileage-tracker/id1408695012) All apps by OverSphere LLC: https://appshunter.io/developer/1181584266 ## Related topics [max effort](https://appshunter.io/ios/topics/max-effort) · [heart zones training](https://appshunter.io/ios/topics/heart-zones-training) --- *Data collected daily from the US App Store and indexed by [AppsHunter](https://appshunter.io/). User reviews are verbatim App Store reviews. Ratings, prices and chart positions refresh continuously; this snapshot is from 2026-08-05.*