Norwegian 4x4 Protocol2.5 - App Store

Norwegian 4x4 HIIT Timer - Interval Training & VO2 Max

BOOST VO2 MAX WITH NORWEGIAN 4X4 PROTOCOL WORKOUTS

Train smarter with the Norwegian 4x4 protocol, one of the most studied HIIT methods for improving cardiovascular performance and endurance. A precise, distraction-free timer guides every interval so you can focus on the effort.

KEY FEATURES:

- Norwegian 4x4 Timer - Precision 4min work / 3min rest cycles
- Heart Rate Training - Track 90-95% max HR zones
- VO2 Max Improvement - Scientifically proven results
- HIIT Interval Timer - Multiple workout protocols
- Progress Tracking - Monitor your fitness transformation
- Universal Training - Running, cycling, rowing, any cardio, you name it
- Offline Ready - No internet required during workouts
- Haptics Feedback and Vibrations
- Countdown before the start
- Customizable Warmup session length
- Customizable Cooldown session length

WHAT IS NORWEGIAN 4 BY 4 TRAINING?

The Norwegian 4x4 protocol is a revolutionary HIIT method featuring:

- 4 intervals of 4 minutes at 90-95% max heart rate
- 3 minutes active recovery between intervals
- Proven results: Increase VO2 max by up to 10% in 8 weeks
- Elite approved: Used by professional athletes worldwide

WHY CHOOSE NORWEGIAN 4X4 INTERVAL TRAINING?

- PROVEN RESULTS: Sports science research shows significant cardiovascular improvements
- BEGINNER FRIENDLY: Complete guide for Norwegian 4x4 workout beginners
- CUSTOMIZABLE: Adapt the Norwegian 4 x 4 protocol to your fitness level
- COMPREHENSIVE: Includes warm-up, cool-down, and recovery protocols
- VALIDATED: Mention in Tim Ferriss' Blog

PERFECT FOR:

- Athletes seeking performance gains with Norwegian 4x4 workouts
- Fitness enthusiasts wanting efficient HIIT interval training
- Anyone improving cardiovascular health through proven protocols
- Runners, cyclists, rowers using Norwegian 4x4 interval training

HOW OFTEN NORWEGIAN 4X4?

- Our app includes guidance on optimal training frequency and recovery for maximum VO2 max gains.

START YOUR NORWEGIAN 4X4 TRANSFORMATION

Join thousands who have revolutionised their fitness with the Norwegian 4x4 protocol training. Download the ultimate Norwegian 4x4 workout app now!

Download today and start training with the Norwegian 4x4.

Version History Visual improvements and fixes based on your feedback. Same focused simplicity for your Norwegian 4x4 sessions. Cooldown 4x4 session wrapper added on users feedback (optional, as warm-up). 2.5 Jun 10 Visual improvement and fixes based on feedback from users. Same amazing simplicity and focus on your Norwegian 4x4 HIIT workout. 2.4 Mar 19 Visual improvement and fixes based on feedback from users. Some amazing simplicity and focus on your HIIT workout. 2.3 Feb 24 Improvements of the background locked-screen mode (thanks, Chris, for the feedback). Same simplicity. 2.2 12/20/2025 Improvements of the background mode (thanks Chris for a feedback). Same simplicity. 2.1 12/05/2025 Improved background timer. Same simplicity and classical Norwegian 4x4 Protocol spot-agistic timers. Apply for running, HIIT, rowing, jumping, or any other sport of your choice and follow visual and audio cues. 2.0 11/09/2025 Improved Warm-up screen with customizable timers in Settings, improved HR readings from Apple Health. Added countdown for exercise start, haptic feedback/vibrations and a dynamic/app widget for a lock screen.

Same simplicity and classical Norwegian 4x4 Protocol spot-agistic timers. Apply for running, HIIT, rowing, jumping, or any other sport of your choice and follow visual and audio cues. 1.37 10/23/2025 Thanks to C.A., Maria, Alvaro, March and Matt for the feedback and waiting!

- Improved HR readings from Apple Health
- Fixed audio cues when in background mode, as well as different horn sounds to differentiate the type of workout (intensive vs. cooldown)
- Now our app supports a background timer mode: switch to the Spotify or Garmin app, or just lock your phone and only follow audio cues if you prefer - the time is ticking
- Thanks for being with us all this time! The Norwegian 4x4 app has experienced significant growth over the last few weeks and has been featured on Tim Ferriss' Blog

Same simplicity and classical Norwegian 4x4 Protocol spot-agistic timers. Apply for running, HIIT, rowing, jumping, or any other sport of your choice and follow visual and audio cues. 1.35 09/02/2025 Thanks to Maria, Alvaro, March and Matt for the feedback and waiting!

- Fixed audio cues when in background mode, as well as different horn sounds to differentiate the type of workout (intensive vs. cooldown)
- Improved HR readings from Apple Watch (active workout)
- Now our app supports a background timer mode: switch to the Spotify or Garmin app, or just lock your phone and only follow audio cues if you prefer - the time is ticking
- Thanks for being with us all this time! The Norwegian 4x4 app has experienced significant growth over the last few weeks and has been featured on Tim Ferriss' Blog

Same simplicity and classical Norwegian 4x4 Protocol spot-agistic timers. Apply for running, HIIT, rowing, jumping, or any other sport of your choice and follow visual and audio cues. 1.34 08/28/2025 Thanks to Alvaro, March, Maria and Matt for the feedback and waiting!

- Improved HR readings from Apple Watch (active workout)
- Now our app supports a background timer mode: switch to the Spotify or Garmin app, or just lock your phone and only follow audio cues if you prefer - the time is ticking
- Thanks for being with us all this time! The Norwegian 4x4 app has experienced significant growth over the last few weeks and has been featured on Tim Ferriss' Blog
- Also we did some little polishes and interface improvements.

Same simplicity and classical Norwegian 4x4 Protocol spot-agistic timers. Apply for running, HIIT, rowing, jumping, or any other sport of your choice and follow visual and audio cues. 1.33 08/24/2025 Thanks to March, Maria and Matt for the feedback and waiting!

- Now our app supports a background timer mode: switch to the Spotify or Garmin app, or just lock your phone and only follow audio cues if you prefer - the time is ticking.
- Thanks for being with us all this time! The Norwegian 4x4 app has experienced significant growth over the last few weeks and has been featured on Tim Ferriss' Blog.
- Also we did some little polishes and interface improvements.

Same simplicity and classical Norwegian 4x4 Protocol spot-agistic timers. Apply for running, HIIT, rowing, jumping, or any other sport of your choice and follow visual and audio cues. 1.32 08/19/2025 Thanks to Maria and Matt for the feedback and waiting!

- Now our app supports a background timer mode: switch to Spotify or Garmin app or just lock your phone and only follow audio cues if you prefer - the time is ticking.
- Thanks for being with us all this time! The Norwegian 4x4 app has grown dramatically over the last few weeks and has been mentioned in Tim Ferriss Blog.
- Also we did some little polishes and interface improvements. 

Same simplicity and classical Norwegian 4x4 Protocol spot-agistic timers. Apply for running, HIIT, rowing, jumping, or any other sport of your choice and follow visual and audio cues. 1.31 08/07/2025 Thanks for being with us all this time! The Norwegian 4x4 app has grown dramatically over the last few weeks!

Little polishes and interface improvements. Same simplicity and classical Norwegian 4x4 Protocol spot-agistic timers. Apply for running, HIIT, rowing, jumping, or any other sport of your choice and follow visual and audio cues. 1.30 08/06/2025 Little fixes and improvements. Same amazing simplicity. 1.29 07/08/2025 Little technical improvements and polishing. Same amazing simplicity. 1.28 04/09/2025 Improve calorie calculation accuracy and a little hint "Swift Left for Settings". Same simplicity. Keep rocking! 1.27 01/21/2025 Long awaited by our loyal users: Heart Rate monitoring/displaying on a main screen (subject of your sensors or watch compatibility and if they send the data to Apple Health). The average value over the last two measurements fetches every 5 seconds will be displayed during the Norwegian 4x4 active interval of workout, cooldown or warm-up exercise. It heart rate won't update if your watch or sensor doesn't send HR data constantly to Apple Health. 1.26 01/07/2025 Long awaited by our loyal users: Heart Rate monitoring/displaying on a main screen (subject of your sensors or watch compatibility and if they send the data to Apple Health). The average value over the last two measurements fetches every 5 seconds will be displayed during the Norwegian 4x4 active interval of workout, cooldown or warm-up exercise. 1.25 12/17/2024 Improvements and fixes in accuracy of workouts calculation with and without custom timers, as well as pushing this data to Apple Health. 1.24 11/01/2024 Improvements and fixes in accuracy of workouts calculation with and without custom timers, as well as pushing this data to Apple Health. 1.23 10/31/2024 Improvements and fixes. Same amazing simplicity and dedication to keep your HR and VO₂ Max levels, making your heart younger.

Why is VO₂ Max Important?

VO₂ max, or maximal oxygen uptake, refers to the maximum amount of oxygen your body can utilize during intense exercise. It’s a critical measure of cardiovascular fitness and endurance, used to assess how well your body can use oxygen to generate energy.

VO₂ max is widely regarded as one of the best indicators of cardiovascular health. The higher your VO₂ max, the better your endurance and the more efficient your body is at using oxygen. It’s a key metric for athletes, and improving it offers numerous benefits:

- Enhanced performance in endurance sports.
- Better cardiovascular health and reduced risk of heart disease.
- Improved overall fitness, making daily activities easier.

Heart Rate Zones and Their Impact

Heart rate zones, typically expressed as percentages of your maximum heart rate (HRmax), are categorized as follows:

- Zone 1: Warm-up Zone (50-60% of HRmax) - This is a light-intensity zone used for warming up and cooling down. It’s great for recovery and increasing blood flow without putting too much strain on the heart.
- Zone 2: Fat Burning Zone (60-70% of HRmax) - Known as the “fat-burning zone,” this moderate-intensity range allows for sustained activity and has been found to improve endurance while using fat as the primary fuel source. It’s also optimal for improving cardiovascular health with lower impact on the joints.
- Zone 3: Aerobic Zone (70-80% of HRmax) - Working in this zone enhances your body’s aerobic capacity and strengthens the heart. Recent studies have highlighted that exercising in this range can improve VO₂ max, the body’s ability to use oxygen efficiently.
- Zone 4: Anaerobic Zone (80-90% of HRmax) - This high-intensity zone is associated with HIIT (high-intensity interval training). Pushing the body into this zone improves speed and power and stimulates the cardiovascular system to adapt. HIIT has been shown to be particularly effective for improving VO₂ max, which is closely tied to longevity.
- Zone 5: Red Line Zone (90-100% of HRmax) - This zone is where the body operates at maximum effort. While it’s not sustainable for long durations, pushing yourself into this range helps improve maximal performance and burns the most calories in the shortest time.

Check out our app and start training with Norwegian 4x4 Protocol to make your heart stronger, healthier and younger. 1.22 10/22/2024 Improvements and fixes. Same amazing simplicity and dedication to keep your HR and VO₂ Max levels, making your heart younger. 1.21 10/14/2024 Improvements and fixes. Same amazing simplicity of the app. 1.20 10/01/2024 Tiny bits of polishing and improvements for larger screens like iPhone 16 Max and Max Pro. Same amazing simplicity of the app. 1.19 09/27/2024 We love receiving your feedback and implementing new useful features! This week we've implemented:

1. An optional warm-up routine was added before the main workout (is off by default, but can be switched on in Settings - swipe right on the main screen).
2. The accuracy of calorie calculation is considered (considering warm-up or without).
3. Table with workout history (click on the upper-calorie counter on the main screen).

Special thanks to Louise, Chad and Marc for the contributions!

Please keep the feedback going! How else we can make it better for you? 1.18 09/11/2024