HIIT 4x4

HIIT 4x4

Interval Training Meter

1 ratings
4 reviews
$9.99

Details

  • Released
  • Updated
HIIT 4x4 screenshot #1 for iPhone
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HIIT 4x4 screenshot #3 for iPhone
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About

This app guides you through High Intensity Interval Training (HIIT) workouts using your heart rate as a percentage of your Maximum Heart Rate (MHR). It features a speedometer-style dial to monitor your heart rate zones and provides chimes to keep you in target.

Heart rate zone monitoring
Speedometer-style dial
Warning chimes for out-of-zone heart rate
Workout history storage via Apple Health
Customizable MHR calculation
Structured 4x4 HIIT program
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What's New in HIIT 4x4

1.09

June 26, 2026

ios 27 support

User reviews

Worked until today

This was a great app for a Norwegian 4x4. Its simplicity was a strength. However, with the latest WatchOS, it will no longer start up via the watch touchscreen on my v8 cellular watch. Bummer.

My 3 stars is the average of a 5 and a 0, sort of. Hoping this gets fixed.

After a delay, here’s an update. The app did start working again after a week or so. My initial POV of good simplicity fell away when I realised that it was merely reporting HR data, but not any GPS, pace, cadence, stride, etc.

I tried using the Apple workout app simultaneously, but HIIT would lock up. Because this app used the same audio alert for starting/stopping an interval and being in the target HR or getting too high or low, I completely missed starting an interval. When I cancelled this app, and just used the built in Timer app, I discovered that my Workout app had been stopped as well.

I just deleted this completely. Waste of time.
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Worked until today

This was a great app for a Norwegian 4x4. Its simplicity was a strength. However, with the latest WatchOS, it will no longer start up via the watch touchscreen on my v8 cellular watch. Bummer.

My 3 stars is the average of a 5 and a 0, sort of. Hoping this gets fixed.

No info on Charges

Never really used the app. I can’t find a place where I can cancel the charges on this app if I decide I don’t want to keep using it. I paid $1.99 but it’s not clear if it renews automatically or is it just a one time charge.?. Doesn’t show on subscriptions on iPhone. Frustrating.

Response from developer

The price is a once only purchase, not a subscription. Please apply to Apple for refunds, google "apple app store refunds"

Not worth the money

I spend too much time looking at my watch to see where my heart rate is at. It distracts from the actual work out. This was a waste of 2 bucks. Avoid!

Response from developer

The app emits tones when you are in the right heart range and when time intervals end -- you don't need to look at it.

Developer apps

FAQ

What is the workout structure for HIIT 4x4?

HIIT 4x4 follows a structured 4x4 program. It includes a 10-minute warmup at 60% MHR, followed by 4 minutes of high intensity at 90% MHR and 3 minutes of low intensity at 70% MHR. This high-low interval cycle is repeated four times.

How does HIIT 4x4 measure exercise intensity?

Intensity is measured as a percentage of your Maximum Heart Rate (MHR). The app uses a speedometer-style dial to show if your heart rate is within the target zone for each interval.

Does HIIT 4x4 store workout data?

Yes, HIIT 4x4 stores your workout history by integrating with Apple Health. This allows you to track your progress over time.

What devices is HIIT 4x4 compatible with?

HIIT 4x4 is designed for Apple Watch and is also supported on iPhone and iPod devices.

How is MHR calculated in HIIT 4x4?

The app uses a commonly used formula of 220 minus your age in years to estimate MHR. It also suggests that a more accurate MHR can be found using a heart monitor during intense exercise.

What happens if my heart rate falls out of the target zone?

If your heart rate deviates from the target interval range, HIIT 4x4 will issue warning chimes until your heart rate returns to the desired zone.

What is the age rating for HIIT 4x4?

HIIT 4x4 has an age rating of 12+. This indicates it is suitable for users aged 12 and older.

How often is HIIT 4x4 updated?

The latest version of HIIT 4x4 is 1.08, and it was last updated on September 20, 2024. This suggests regular updates to maintain functionality.