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Fjell (say "fyell") is Norwegian for mountain. After a session, the recap graph shows the four work intervals as four peaks.

In one line

Fjell is an iPhone and Apple Watch app for the Norwegian 4x4 interval workout, steered by your heart rate.

In 50 words

In 120 words

Fjell is an iPhone app for the Norwegian 4x4 interval workout: four rounds of 4 min at 90 to 95 % of max heart rate, with 3 min of easy recovery in between. Apple Watch measures your heart rate, and Fjell shows whether you are below, in or above the zone. A halfway check, Fjell's own rule of thumb, shows if you are on pace for the zone. Voice cues play over your music, and a Live Activity shows the workout on the lock screen. After each session, a graph shows your four peaks and time in zone. Recovery shows overnight heart rate variability against your own baseline. No account. Your data stays on your iPhone and in Apple Health.

Key facts

Name: Fjell, said "fyell": Norwegian for mountain
What it is: An iPhone app with an Apple Watch app and a lock-screen Live Activity, for the Norwegian 4x4 interval workout
Category: Health & Fitness
Price: 7 days free for new subscribers, then 2.99 a month or 19.99 a year (in USD, CAD and EUR; local prices elsewhere)
Works with: iPhone. Apple Watch is optional and adds heart rate. See the requirements.
Privacy: No account, no ads, no tracking. Data stays on the iPhone and in Apple Health.
Developer: David van Rooij
Contact: [email protected]