Know your true fitness.
Train to
improve it.

VO2 max is the maximum amount of oxygen your body can use during intense exercise, usually expressed in mL/kg/min. It reflects cardiorespiratory fitness, a strong predictor of long-term health and mortality. Improving it builds capacity for exercise and everyday life.

VO2 Maximizer guides you through five performance-based field tests:

• Beep test: progressive 20-metre shuttles.
• Yo-Yo test: intermittent shuttles with recovery.
• Cooper test: cover as much distance as possible in 12 minutes.
• Balke test: cover as much distance as possible in 15 minutes.
• 2.4 km test: complete the distance as quickly as possible.

Field tests estimate VO2 max using performance and a test-specific equation. Pacing, terrain, weather and test setup affect the result. A laboratory test with respiratory-gas analysis measures oxygen consumption directly. Use the same field test and similar conditions to track your progress.

Allow roughly 8 minutes for a Beep or Yo-Yo test and 13 minutes for a 2.4 km run as planning estimates, plus time to warm up. Shuttle tests end when you can no longer keep up; the 2.4 km duration depends on your running pace.

Build a repeatable routine with a balance of training and recovery:

• Use HIIT sessions to challenge your aerobic capacity.
• Add easier Zone 2 sessions to build endurance.
• Allow recovery between demanding sessions.
• Retest under similar conditions to follow your progress.

The interval patterns differ:

• Norwegian 4×4: four 4-minute work intervals, with 3-minute active recoveries between them.
• Tabata: 20 seconds of work and 10 seconds of rest, typically repeated eight times.
• 30/30: alternating 30-second work and recovery periods.

Yes. Follow live heart-rate guidance on iPhone with Apple Watch or a compatible Bluetooth heart-rate strap. Audio cues help you follow the session through your headphones.

No. VO2 Maximizer is available on iPhone, with a companion Apple Watch experience for wrist-based heart rate and workout cues. A compatible Bluetooth strap is another option for heart-rate training.

Fitness age puts your VO2 max in an age-related context. The 12-week projection shows an estimated training trajectory, helping you connect your starting point with your plan.

Choose a target from your own past performances, world records or other people on the leaderboard. Ghost Race shows your position relative to that performance as you run.

Live Activities keep supported sessions visible on your Lock Screen. Depending on the session, you can see remaining time, distance, pace, heart rate or interval progress.

Yes. Use a built-in preset or create your own work and recovery blocks.

Yes. The app is free to download with in-app purchases. The App Store shows current prices and available offers for your region.