# Peak Intervals: Norwegian 4x4 — VO2 Max & Zone 2 Training

> VO2 Max & Zone 2 Training (iPhone/iPad app by Justin Polidori.)

- Source: https://appshunter.io/ios/app/peak-intervals-norwegian-4x4/id6757667069 (this page in markdown: same URL + `.md`)
- Developer: [Justin Polidori](https://appshunter.io/developer/1866410754)
- Category: Health & Fitness
- Price: Free with in-app purchases
- Age rating: 17+
- Requires: iOS 26.0 · 18 MB
- Languages: American English, Danish, French (France), German (Germany), Italian, European Portuguese, Slovak, European Spanish
- Released: 2026-02-05
- Data updated: 2026-10-11

## What is Peak Intervals?

Peak Intervals guides two endurance workouts on Apple Watch: the Norwegian 4x4 to train your VO₂ max, and steady Zone 2 sessions to build your aerobic base. Your iPhone follows along live and shows how each session went.

Guided workouts need Apple Watch and a Peak Intervals Pro subscription, with a 2-week free trial where available. History, Trends and the analysis of your Apple Health workouts are free.

NORWEGIAN 4x4
• Four 4-minute intervals at 90–95% of your max heart rate, with 3-minute recoveries.
• Live guidance keeps you in the zone: haptic cues on your wrist, and voice cues with headphones.
• Afterwards, see whether you reached the zone quickly, stayed in it during every interval, held your pace or power from the first interval to the last, and how fast your heart rate came down in each recovery.

ZONE 2
• Run, ride, row or walk on an incline, indoors or outdoors, with a guided warm-up and cool-down.
• An alert tells you when you drift out of the zone, and a talk test at 15 minutes asks how the effort feels.
• Afterwards, see how much of the session you spent in the zone, whether your heart rate crept up at the same effort (decoupling), and how your power or pace at Zone 2 heart rate compares with your last session of the same activity.

ZONES THAT FIT YOU
• Your max heart rate starts from an age estimate and goes up if a recent workout in Apple Health reached a higher heart rate.
• Zone 2 uses your Apple Health heart rate zones on iOS 27, or your resting and max heart rate.
• Your talk test answers help tune the zone: after three easy sessions the app offers to raise it, and when talking gets hard it offers to lower it. You decide.

TRENDS AND HISTORY
• Compare your last 3 sessions with the 3 before, with a clear verdict such as Improving or Stable.
• See your VO₂ max and resting heart rate from Apple Health next to your training.
• Every session in one place, including workouts from Apple Health.
• Share a session as a story or post, with your own photo in the background.

APPLE WATCH AND iPHONE
Workouts start and record on Apple Watch. Your iPhone follows live, also on the Lock Screen and in the Dynamic Island.

Apple Health
Peak Intervals reads workout and heart rate data from Apple Health (HealthKit) to calculate your metrics and trends. You control what is shared at any time in iOS Settings.

Subscriptions
Peak Intervals offers an auto-renewing subscription with monthly and yearly plans, including a 2-week free trial where available. After the trial, an active subscription is required to start new workouts. Payment is charged to your Apple ID account at confirmation of purchase. Subscriptions renew automatically unless canceled at least 24 hours before the end of the current period. You can manage or cancel your subscription in App Store account settings.

Peak Intervals is not a medical device and does not provide medical advice. High-intensity exercise may not be appropriate for everyone. Consult a physician before beginning a new training program.

Privacy Policy: https://peakintervals.app/privacy
Terms of Use: https://peakintervals.app/terms

## Pricing and in-app purchases

Base price: Free.

**Subscriptions**

| Subscription | Price | Period |
| --- | --- | --- |
| Pro | $9.99 | per month |
| Pro Yearly | $49.99 | per year |


## Is Peak Intervals safe?

Not enough ratings yet to assess Peak Intervals.

## Is Peak Intervals legit?

Peak Intervals: Norwegian 4x4 appears legitimate, with a few gaps. The AppsHunter Legitimacy Score for Peak Intervals is 65 out of 100 points across 7 verification signals from App Store and developer data.


## Version history (last 5 releases)

### 2.1.1 — 2026-10-05

New: Trophies. Tap the trophy button on Home, top right; a dot shows when something is new. The first time, a short intro counts through your workout history and every trophy you already earned pops in.

• Milestones: your 1st, 10th, 25th, 50th and 100th 4x4.
• Ways to train: your first, 10th and 25th 4x4 running, cycling and rowing, plus All-rounder for all three.
• Distance in intervals: a marathon run, the Channel rowed (34 km) and 100 km ridden, added up inside your 4x4 intervals.
• Consistency: 4 and 12 weeks in a row.
• Training quality: Locked in (all four intervals at 90–95% of max heart rate) and Balanced week (a 4x4 and a Zone 2 in one week).
• Zone 2 base: your first Zone 2, then 10, 25 and 50, and the Steady hour.
Turn a medal over to see the date you earned it, and share any trophy as a story or post card. Trophies are personal: no leaderboards. Free for everyone.

• Apple Watch complication: this week's sessions on every face, including the corner one; the rectangular style adds "Last 4x4: 72%". A session you just recorded shows at once, and it rises in the Smart Stack after 2+ days without training.
• Start faster: the Action button and Siri start a 4x4 or Zone 2 ("Start Zone 2 in Peak Intervals"); Double Tap pauses, resumes, starts your first listed workout, or closes the summary; a new Control Center control shows how to start on Apple Watch.
• Apple Watch accessibility: text follows your watch's text size; VoiceOver reads heart rate with zone status and timers and announces phase and zone changes; the zone label adds ↑ ↓ beside the color; Reduce Motion is respected.
• iPhone: Liquid Glass buttons, a tab bar that shrinks on scroll, and a bar above the tabs with phase and heart rate during a Watch workout (iOS 26.1+). Larger text no longer cuts off the 4x4/Zone 2 switch or Home tips.

### 2.0.2 — 2026-10-03

New: Zone 2 on Apple Watch. Build your aerobic base with steady sessions and push your VO₂ max with the Norwegian 4x4, both guided on your wrist.

• Widgets: see your training week and your last 4x4 on the Home Screen and Lock Screen.
• Siri: ask "How's my week in Peak Intervals?" or "Show my last 4x4 in Peak Intervals."

### 2.0.1 — 2026-09-29

Zone 2 is here. Build your aerobic base alongside your 4x4, with Apple Watch guiding you.

ZONE 2
• Run, ride, row or walk on an incline in your Zone 2, indoors or outdoors, with a guided warm-up and cool-down.
• Apple Watch lets you know when you drift out of the zone, and a talk test at 15 minutes checks how the effort feels.
• Your zone comes from your Apple Health heart rate zones on iOS 27, or from your resting and max heart rate. When sessions feel easy, the app suggests raising it.
• After each session: time in zone with a clear verdict, heart rate with power or pace, decoupling, and your power or pace at Zone 2 heart rate compared with your last session of the same activity.
• Heart rate sensor glitches are filtered out of your numbers.
• iPhone follows Zone 2 workouts live, and the Live Activity turns blue.

HOME, TRENDS AND HISTORY
• Switch between 4x4 and Zone 2 on Home, Trends and History.
• Your fitness: VO₂ max and resting heart rate from Apple Health, side by side on Home.
• Zone 2 Trends: decoupling, time in zone, resting heart rate and Zone 2 minutes per week. The 4x4 view now shows your Apple Health cards too.

APPLE WATCH
• A new start screen: pick 4x4 or Zone 2 and change the options right on your wrist.
• A 3-2-1 countdown before every workout.
• End a 4x4 during the warm-up and choose whether to save it.
• Fixes an error message that could appear right after you end a workout.

ALSO NEW
• A redesigned onboarding that builds your heart rate zones from Apple Health, including your max heart rate from your hardest recent workout.
• Share any session as a story or a post, with your own photo in the background.
• Settings now explain how your max heart rate is set.

### 2.0.0 — 2026-09-28

Zone 2 is here. Build your aerobic base alongside your 4x4, with Apple Watch guiding you.

ZONE 2
• Run, ride, row or walk on an incline in your Zone 2, indoors or outdoors, with a guided warm-up and cool-down.
• Apple Watch lets you know when you drift out of the zone, and a talk test at 15 minutes checks how the effort feels.
• Your zone comes from your Apple Health heart rate zones on iOS 27, or from your resting and max heart rate. When sessions feel easy, the app suggests raising it.
• After each session: time in zone with a clear verdict, heart rate with power or pace, decoupling, and your power or pace at Zone 2 heart rate compared with your last session of the same activity.
• Heart rate sensor glitches are filtered out of your numbers.
• iPhone follows Zone 2 workouts live, and the Live Activity turns blue.

HOME, TRENDS AND HISTORY
• Switch between 4x4 and Zone 2 on Home, Trends and History.
• Your fitness: VO₂ max and resting heart rate from Apple Health, side by side on Home.
• Zone 2 Trends: decoupling, time in zone, resting heart rate and Zone 2 minutes per week. The 4x4 view now shows your Apple Health cards too.

APPLE WATCH
• A new start screen: pick 4x4 or Zone 2 and change the options right on your wrist.
• A 3-2-1 countdown before every workout.
• End a 4x4 during the warm-up and choose whether to save it.

ALSO NEW
• A redesigned onboarding that builds your heart rate zones from Apple Health, including your max heart rate from your hardest recent workout.
• Share any session as a story or a post, with your own photo in the background.
• Settings now explain how your max heart rate is set.

### 1.2.9 — 2026-09-25

A new design, and ready for iOS 27 and watchOS 27.

NEW DESIGN
• Home, Session Detail, History and Trends now fit on one screen, with the same look on iPhone and Apple Watch.
• Home: your last session at a glance, with time in zone for each interval, one insight at a time, and your week.
• Session Detail: heart rate with the 90–95% band, the zone split of every interval, your strongest and least efficient rep, and each recovery.
• Trends: last 3 sessions vs the 3 before, plus time in zone for every session, now also for All time.
• History: your mix of activities and indoor vs outdoor sessions.

iOS 27 AND watchOS 27
• On watchOS 27, each workout sets the 4x4 heart-rate zones, so Health and Fitness show your time in each band.
• Follow your Apple Watch workout on the Lock Screen and in the Dynamic Island.
• Start a 4x4 with the Action button on Apple Watch Ultra, and open the app from the new watch face complication.

WORKOUTS
• Workouts start and record on Apple Watch. iPhone follows live and shows the saved session.
• Live data on iPhone reconnects if the connection drops mid-workout.

FIXES
• Distance no longer adds iPhone steps on top of Apple Watch data. Past sessions are recalculated.
• Your HRmax and indoor/outdoor settings now reach Apple Watch reliably.
• Warmup data is kept if the Watch app restarts during a workout.
• Voice cues no longer leave your music quieter.
• Trend changes now match the numbers shown, with time in zone in percentage points.
• The Live Activity ends when the workout ends.
• Better Dynamic Type and VoiceOver support, including audio graphs for charts.

## Apps similar to Peak Intervals

| App | Rating | Price | Category |
| --- | --- | --- | --- |
| [Ramp4x4: VO2 Max Trainer](https://appshunter.io/ios/app/ramp4x4-vo2-max-trainer/id6768789400) | 5.0 (1) | Free | Health & Fitness |
| [Norwegian 4x4 Coach](https://appshunter.io/ios/app/norwegian-4x4-coach/id6782398289) | — | Free | Health & Fitness |
| [4x4 HIIT](https://appshunter.io/ios/app/4x4-hiit/id6755360081) | — | Free | Health & Fitness |
| [PeakInterval: HIIT Timer](https://appshunter.io/ios/app/peakinterval-hiit-timer/id6790185600) | — | Free | Health & Fitness |
| [VO2 Flow: Norwegian 4x4 Timer](https://appshunter.io/ios/app/vo2-flow-norwegian-4x4-timer/id6757104585) | — | Free | Health & Fitness |
| [PointFit App](https://appshunter.io/ios/app/pointfit-app/id6740024306) | — | Free | Health & Fitness |

## More apps by Justin Polidori

- [Trainwise IQ](https://appshunter.io/ios/app/trainwise-iq/id6757368895)
- [CutRoll: Reel & Story Maker](https://appshunter.io/ios/app/cutroll-reel-and-story-maker/id6798736720)
- [Shotcurve: GLP-1 Shot Tracker](https://appshunter.io/ios/app/shotcurve-glp-1-shot-tracker/id6801506970)

All apps by Justin Polidori: https://appshunter.io/developer/1866410754

## Related topics

[norwegian 4x4 coach](https://appshunter.io/ios/topics/norwegian-4x4-coach) · [norwegian 4x4 heart rate](https://appshunter.io/ios/topics/norwegian-4x4-heart-rate) · [norwegian 4x4 workout](https://appshunter.io/ios/topics/norwegian-4x4-workout)

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*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 2026-10-11.*