3.3.1. Screening and Recruitment

Members of the University of California Berkeley community were sought for participation in this study. Potential participants were screened according to two criteria. First, participation was only allowed to those who are current long-distance runners. This requirement was placed in an effort to not subject the study participants to the risks of running, if they do not regularly run (e.g., injury). By limiting participation in the study to those who regularly run long distances, we are taking measures to minimize the risks of participation in the study. For screening purposes, we use the definition of "long-distance runner" that is used by the International Association of Athletics Federations (IAAF), which states the following:

A long-distance runner is someone who every week (i) runs for at least 5 km (or 3 miles) in distance; or (ii) runs at least one session that is 1 h or longer in duration.

The second screening criterion limited participation to subjects who owned an Android smartphone running Android 4.3 (Jelly Bean MR2) or newer. This requirement allowed us to better assess acceptability and usability qualities of the proposed system, by requesting that participants use their own smartphones for the purposes of the study. In turn, any feasibility or usability issues arising from using an unfamiliar smartphone, if it were to be provided by the study, are thus eliminated.

After the screening of each candidate subject, the researcher administering the process obtained her or his consent for participation in the study. After the consent process, the researcher conducted the initial set up procedure for the subject. This procedure entailed providing the subject with a Jarv Run heart rate chest strap monitor [41]. Afterwards, the RunningCoach app was installed on the subject's smartphone and paired with the heart rate monitor. Subsequently, the subjects were instructed on the proper way of using the system by providing instructions specific to pre-, during, and post-running use (e.g., how to wear the heart rate chest strap, where to secure the phone during the run, etc.). Finally, the researcher demonstrated the use of the RunningCoach app and its features to the subject. The subjects were encouraged to ask any questions related to the system or the protocol.

In total, six subjects were recruited for the study. The study spanned from February 2017 to July 2017. The subject demographics and physical parameters are summarized in Table 1.


**Table 1.** The demographics of the recruited subjects.
