On iOS, without an Apple Watch, how to collect totalEnergyBurned for a workout?

When saving a workout to the iOS health store, without any Apple Watch, how should an app calculate totalEnergyBurned?

The Apple uses a hard coded value for totalEnergyBurned, but says a real-world app would calculate this values from sensor data.

HKQuantity *energyBurned = [HKQuantity quantityWithUnit:[HKUnit kilocalorieUnit] doubleValue:425.0];

HKQuantity *distance = [HKQuantity quantityWithUnit:[HKUnit mileUnit] doubleValue:3.2];

HKWorkout *run = [HKWorkout workoutWithActivityType:HKWorkoutActivityTypeRunning
                                          startDate:start
                                            endDate:end
                                           duration:0
                                  totalEnergyBurned:energyBurned
                                      totalDistance:distance
                                           metadata:nil];

[self.healthStore saveObject:run withCompletion:^(BOOL success, NSError *error) {
}];

Thank you

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