Peak Intervals vs Circuit Timer

Peak Intervals helps you train VO₂max using the Norwegian 4x4 interval method and track training quality over time. Run, ride, or row a 4x4 session, stay in your target heart rate zone, then review clear metrics that explain workout quality and progress over time. What you get: • Guided 4x4 workouts with Apple Watch support • Target heart rate zone guidance based on 90–95% of estimated HRmax • Time in Zone (≥90% HR) to measure intensity • Repeatability to see if you hold performance from interval 1 to 4 • Recovery to measure how fast your heart rate drops between intervals • Trends and simple verdicts like Improving, Stable, Under-target, or Fatigued • Workout history with interval breakdowns and session details Apple Health Peak Intervals can read workout and heart rate data from Apple Health (HealthKit) to compute 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

Build custom interval training circuits and run them with precision timing, voice announcements, and haptic feedback. CREATE YOUR PERFECT WORKOUT Design circuits with unlimited intervals, each with its own name, duration, and alarm sound. Set loop counts on individual intervals or the entire circuit. Choose from 24 alarm sounds, enable voice countdown, or both. STAY IN THE ZONE A full-screen player with a progress ring, countdown timer, and interval timeline keeps you focused. The last 3 seconds pulse to keep you ready for what's next. Voice announcements call out interval names so you never have to look at your screen. NEVER MISS A BEAT Live Activities put your timer on the Lock Screen and Dynamic Island. Background notifications keep you on track even when you switch apps. Start circuits hands-free with Siri. APPLE WATCH Run circuits from your wrist with real-time heart rate zones, active calories, and haptic alerts. Your watch keeps going even when the screen dims with Always-On Display support. TRACK YOUR PROGRESS View workout history with streaks, completion stats, and total training time. Save workouts to Apple Health as High Intensity Interval Training sessions. FREE TO START - 1 circuit with full features — alarms, haptics, voice, history CORE UPGRADE - Unlimited circuits - iCloud sync across devices - Apple Health integration PRO UPGRADE - Everything in Core - Apple Watch companion app Terms of Use: https://www.apple.com/legal/internet-services/itunes/dev/stdeula/