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# HKMetadataKeyVO2MaxValue

The maximum oxygen consumption rate during exercise of increasing intensity.

```
let HKMetadataKeyVO2MaxValue: String
```

## Discussion

The system sets this key on [`lowCardioFitnessEvent`](/documentation/HealthKit/HKCategoryTypeIdentifier/lowCardioFitnessEvent) samples. It contains the value of the VO2 max measurement that triggered the event. The value of this key is an [`HKQuantity`](/documentation/HealthKit/HKQuantity) object with a unit of `ml/kg/min`. For more information on working with complex units, see [`unitMultiplied(by:)`](/documentation/HealthKit/HKUnit/unitMultiplied(by:)), [`unitDivided(by:)`](/documentation/HealthKit/HKUnit/unitDivided(by:)), and [`init(from:)`](/documentation/HealthKit/HKUnit/init(from:)-9qont).

---

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