Peak Intervals: Norwegian 4x4

Peak Intervals guides two endurance workouts with Apple Watch or a Bluetooth heart rate monitor: the Norwegian 4x4 to train your VO₂ max, and steady Zone 2 sessions to build your aerobic base. It shows how each session went.

Guided workouts need Apple Watch or a Bluetooth heart rate monitor, 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 Apple Watch, 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 OR A HEART RATE MONITOR
• With Apple Watch, the workout runs on your wrist with haptic cues, and your iPhone follows live, also on the Lock Screen and in the Dynamic Island.
• With a Bluetooth heart rate monitor paired in iOS Settings, the workout records on your iPhone: live zones on screen, voice cues in your headphones, the Lock Screen and the Dynamic Island. Haptics are Apple Watch only.

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.

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