*5.3. Perceived Accuracy*

As part of the routine post-run surveys, we inquired about the perceived levels of accuracy of the collected data. Concretely, we asked the subjects: "After viewing your run data, were any of the measurements inaccurate to the best of your assessment? (Choose all that apply from Speed, Cadence, Heart Rate, Energy Expenditure, Distance)". The responses to this question are presented in Figure 8b. As follow-up to this question, the subjects were also asked to provide additional information when they thought any measurements were inaccurate.

Energy expenditure was not perceived as inaccurate by the runners. A possible explanation to this is that it is difficult for people to gauge their own energy expenditure during physical activity. For distance, one subject reported: "if you're counting total miles traveled, then it should be closer to 5, but if you're just counting miles run, that's maybe accurate." The measured distance (from GPS data) during this particular run was 3.72 miles, which reflects the total miles traveled. After carefully reviewing the data, it seems that the run monitoring was not started until the runner was in the middle of the run. We concluded this because the runner always took the same route, except in this run where the monitoring started from a middle point in that route (which accounts for the difference in mileage). In the following sections, we discuss in more detail the perceived accuracy for the heart rate and cadence measurements.
