*5.6. Limitations of the Study*

The presented study has several limitations. First, the number of subjects in the study (sample size) is small. While all recruited subjects are considered long-distance runners per definition, their training regimens in total distances traveled per run were quite diverse. Some subjects were in general not users of smartphone apps for running, therefore their expectations and responses may have been different than of the subjects who are users of such applications on a more regular basis. Since the goal of this study was to assess the feasibility and the usability of the developed telemonitoring framework, less emphasis was given on the rigid study protocol that would perhaps result in larger number of collected runs during the three months. The study instead aimed to investigate how often the runners would use RunningCoach app during their runs and what type of information can be extracted from the collected data. A sample of the results was presented in this paper. To evaluate in more detail the running performance of individual runners and their changes over time, given the feedback on the cadence, the subjects in future studies will be required to perform certain number of runs per week. Such data collection across larger pool of subjects would provide the data needed to achieve the long-term goal of this research, i.e., to tune the training models to individual runner's physique and to evaluate the efficacy and potential benefits of such training for prevention of injuries.

Furthermore, feedback from the users indicated that the large form factor of the smartphone may not be as convenient for long-distance runners due to the mounting inconvenience and additional weight. The use of a smartphone for casual monitoring of daily activities may be preferred over wearable devices as people tend to carry their smartphone throughout the day. On the other hand, to measure the athletic performance, wearable sensors may be more convenient. As the Berkeley Telemonitoring framework is compatible with any Android device, the future iterations of this system may include the use of a smart watch or other wearable technology.
