# Zx: Heart Rate Zones Training

> Interval Timer & HIIT Trainer

Canonical page: [https://chrome-stats.com/d/id1457355997](https://chrome-stats.com/d/id1457355997)

## Overview

- **ID:** `id1457355997`
- **Platform:** Apple
- **Type:** Apple app
- **Status:** Available
- **Publisher:** OverSphere LLC
- **Category:** Health & Fitness
- **Rating:** 4.30 / 5 (70 ratings)
- **Version:** 1.8.1
- **Last updated:** 2026-07-18
- **First published:** 2019-12-22
- **Size:** 51 MB
- **Data as of:** 2026-09-25
- **Store listing:** [Apple App Store](https://apps.apple.com/us/app/zx-heart-rate-zones-training/id1457355997)
- **Website:** [https://www.oversphere.net](https://www.oversphere.net/)
- **Privacy policy:** [https://www.oversphere.net/privacy-policy](https://www.oversphere.net/privacy-policy)

## Description

Zx is your personal heart-rate coach for interval training. Create custom interval workouts or download community workouts; official Zx workouts are updated regularly. Zx supports Apple Watch or any compatible Bluetooth heart rate monitor, and it integrates with the Health app to surface your heart-rate zones and training stats.

Key features include Guided Interval Training, Open Mode on Apple Watch, custom workout creation, and a library of community workouts to download and remix. Track daily, weekly, and monthly stats and plan future sessions to improve fat burn, VO2 max, and overall performance.

## Rankings

- #158,937 — Overall
- #81 — effort

## Review summary

Overall sentiment is mixed. Some users praise the app’s concept, interval timing, and customization options, and even report health benefits. However, multiple reviewers consistently cite Apple Watch syncing problems (workouts not appearing, spinning, or failing to sync), issues with self-created workouts, and general stability glitches. Support quality and documentation are also cited as poor by several users. In short, the app has promising features, but recurring syncing, reliability, and support problems dominate the user experience.

### Cons

- Persistent Apple Watch synchronization issues: workouts not appearing on the watch, watch not syncing with the iPhone app, and occasional spinning.
- App stability problems: crashes or shutdowns during editing and general glitches.
- Poor support and outdated or placeholder documentation/website; slow or unhelpful responses.
- Custom/self-created workouts frequently fail to sync or appear on the watch.

## Similar extensions and apps

- [Simple Zones](https://chrome-stats.com/d/id1533922808) — 4.00 / 5
- [Zones for Training](https://chrome-stats.com/d/id1139688415) — 4.80 / 5
- [Cardio Zones.](https://chrome-stats.com/d/id1103232564) — 4.30 / 5
- [HeartOxy](https://chrome-stats.com/d/id6757838240)
- [Heart Zones Workout](https://chrome-stats.com/d/id1578321963) — 4.50 / 5
- [HR Zone Monitor](https://chrome-stats.com/d/id6759027810)
- [Heart Rate Zones Trainer](https://chrome-stats.com/d/id6772269496)
- [Intervals - the training timer](https://chrome-stats.com/d/id6736897379) — 4.00 / 5
- [Ares - Workout Interval Timer](https://chrome-stats.com/d/id6743498963) — 5.00 / 5
- [HR Zones Weekly](https://chrome-stats.com/d/id6766235464)
- [RunnersHeart](https://chrome-stats.com/d/id6758222219)
- [ZoneCoach - Hear Your Zone](https://chrome-stats.com/d/id6762046530)

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Source: [Chrome-Stats](https://chrome-stats.com/d/id1457355997)