| -Accuracy of monitoring variables |
The accuracy of smartwatches in measuring heart rate varies, and none are as accurate as an electrode-containing chest monitor, which approaches the accuracy of an ECG [1]. The accuracy of wrist-based devices can also be affected by factors such as body temperature, hemoglobin levels, skin status, and blood pressure [1,5]. |
Acquiring better wrist-based devices or combining them with bellyband HR measuring devices would help to lower the bias that smartwatches are subject to. |
| -Disturbances related to wearing smartwatches |
Monitoring both heart rate and quality of sleep implies wearing the smartwatch 24/7, even in situations where the participant may be not used to it, such as wearing the device while sleeping. Almost half the participants complained about the watches being uncomfortable for sleeping or doing their everyday tasks during the first week of the study. One participant also reported an allergy, developing a skin rash on the wrist where the device was worn. |
Strategies were adopted to allow participants that reported discomfort to remove the device during the day or at night in between groups of activities. Since the allergy was reported in the interval between the walking and control sessions, the device was removed until the allergy disappeared. No further allergy episodes were reported. |
| -Not activating the device while performing the activities |
Although a training session was held prior to the start of the study where it was explained to participants how to use and charge their devices, some of them experienced difficulties using them. Although we tried to make sure that every device was registering the training session, on very few occasions a participant's device was not activated. |
It is advisable to remind participants to turn on their devices and always ensure that all the smartwatches are activated before starting the activity. |
| -Device malfunctioning |
The devices malfunctioned several times, although we do not know if this was a device error or due a participant tampering with the watch, so the HR of some patients stopped being recording on several occasions. Although we always had each patient's smartwatch register to hand and we were able to resolve errors as soon as they were detected, a couple of incidents did remain undetected, leading to a loss of data about HR and sleep quality (dependent on the HR monitoring function being activated). |
We strongly recommend reviewing the smartwatches' recording history every day and resolve problems detected due to malfunctioning as soon as possible. |
| -Removal of the devices |
Cases of the participant removing the smartwatch without informing the research team occurred. Despite most of the cases being rapidly detected and the participants redressing the problem, in one case the participant did not follow the research team's repeatedly given instructions and wore the device only during the training sessions. Therefore, the data obtained from this participant is scarce. |
We strongly recommend revising smartwatch's’ recording history every day and assure that all the devices are recording all the parameters. |
