# 4x4 HIIT — Norwegian 4x4 HIIT Trainer

> Norwegian 4x4 HIIT Trainer (iPhone/iPad app by SIA Valabijs.)

- Source: https://appshunter.io/ios/app/4x4-hiit/id6755360081 (this page in markdown: same URL + `.md`)
- Developer: [SIA Valabijs](https://appshunter.io/developer/1853404704)
- Category: Health & Fitness
- Price: Free
- Age rating: 17+
- Requires: iOS 17.0 · 2 MB
- Languages: American English
- Released: 2025-11-18
- Data updated: 2026-05-17
- User reviews in markdown: https://appshunter.io/ios/app/4x4-hiit/id6755360081/reviews.md

## What is 4x4 HIIT?

Transform your cardiovascular fitness with the Norwegian 4x4 HIIT protocol - the scientifically-backed method used by elite athletes and researchers to dramatically improve VO2 max and heart health.

WHAT IS 4x4?
Four intervals of 4 minutes at high intensity (85-95% max heart rate), separated by 3 minutes of active recovery. That's it.

WHY IT WORKS
Developed by Norwegian exercise scientists, this protocol has been proven in clinical studies to:
- Increase VO2 max faster than traditional cardio
- Improve cardiovascular health
- Boost endurance and athletic performance
- Deliver maximum results in minimum time

SIMPLE TO USE
- Clear visual timer with audio cues
- Tracks your intervals automatically
- Works with any activity: running, cycling, rowing, or body weight exercises
- No complicated setup - just hit start

PERFECT FOR
- Runners looking to improve race times
- Athletes building aerobic capacity
- Anyone wanting efficient, science-backed cardio
- People with limited time for training

The Norwegian 4x4 protocol is one of the most researched and effective HIIT methods available. Stop guessing. Start training with proven science.

Download now and take the first step toward your best cardiovascular fitness.


## Version history (last 3 releases)

### 1.2 — 2026-03-01

We've made some app improvements and bug fixes.

### 1.1 — 2025-11-23

We've made some app improvements and bug fixes.

### 1.0 — 2025-11-18

No release notes.

## Related topics

[4x4 hiit](https://appshunter.io/ios/topics/4x4-hiit)

---

*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 2026-05-17.*