Estimation of Distance (non-smart treadmills)
If you're on a treadmill that doesn't have bluetooth functionality, we'll automatically estimate the distance that your treadmill is at, based on the time of the workout and the set speed of the workout. For example, if the Runna app sets your run at 10kph and you run for 1 hour, we'll assume you'll have travelled 10km.
In reality, the treadmill belt will take a while to accelerate and in practice you might have only travelled 9.9km in this time. However since the belt speed is unique to each and every treadmill and we don't want to show that you've missed your pace targets because the belt took a while to speed up, we set your distance to 10km and thus average speed to 10kph.
Adjustment of Time (smart treadmills)
To take into account the acceleration and deceleration of the treadmill belt - which can vary significantly depending on the treadmill you are using - we process the data from our smart treadmill activities throughout the workout to ensure that you are still hitting your pace targets within the Runna app.
As mentioned above, without these adjustments, your average pace would include the time taken for the treadmill to get up to speed - which can result in your average lap pace differing from the target for that lap. This is especially prominent on short, faster laps, where average pace values can be around 15 seconds/km off the target pace set on the treadmill. To combat this, our calculations assume that you have reached your target speed as soon as the step begins. This negates the effect of treadmill acceleration/deceleration.
Your expended effort should balance out over the course of a workout. This is because although it takes time to get up to a faster speed, it also takes time to return to the original speed.
For a more visual representation of what is happening behind the scenes, see the following graph. Importantly, the final value of your average lap time after processing matches the speed set on the treadmill. Without processing, there is a clear deviation in average lap pace over the lap.