· · · Repository hosted by TU Delft Library

Prolonged sitting time is a potential health risk, not only for people with an inactive lifestyle, but also for those who do meet the recommended amount of physical activity. In this paper, we evaluate SitCoach, a mobile application to nudge people from their seats. SitCoach monitors physical activity and sedentary behavior to provide timely feedback by means of suggesting sitting breaks. A pilot experiment with a group of 8 users learned that the general awareness of the importance of sitting breaks is low. Combined with the belief that the ability to take sitting breaks is highly dependent on externalfactors, a strategy of proposing break reminders may not be the most successful for this target group. Future work should focus on creating awareness of the problem and providing insights into personal sitting behavior.

The advancement of current technology allows developing lightweightunobtrusive devices, which detect human physical activity. However, there has always been a major issue, hindering the regular usage ofthese gadgets - many people find it difficult to fit them in theirdaily routine. In this thesis, we develop an application, which allows us to measure the influence of online social networks on people involved in physical activity programs. On the grounds of our literature research, we identify different motivational triggers that can be employed for the design of a social network application in the context of physical activity programs. Based on these findings, we design and implement the ActiveTeam application, using Facebook as underlying social network service. In the course of the document we propose several methods to evaluate the behaviour of ActiveTeam users. These methods areintended to help us analyze and improve the application once it ismade available to a large number of users.

Accurate identification of physical activity types has been achieved in laboratory conditions using single-site accelerometers and classification algorithms. This methodology is then applied to free-living subjects to determine activity behaviour. This study aimed at analysing the reproducibility of the accuracy of laboratory-trained classification algorithms in free-living subjects during daily life. A support vector machine (SVM), a feed-forward neural network (NN) and a decision tree (DT) were trained with data collected by a waist-mounted accelerometer during a laboratory trial. The reproducibility of the classification performance was tested on data collected in daily life using a multiple-site accelerometer (IDEEA) augmented with an activity diary for 20 healthy subjects (age: 30 ± 9; BMI: 23.0 ± 2.6 kg/m2). Leave-one-subject-out cross-validation of the training data showed accuracies of 95.1 ± 4.3%, 91.4 ± 6.7% and 92.2 ± 6.6% for the SVM, NN and DT, respectively. All algorithms showed a significantly decreased accuracy in daily life as compared to the reference truth represented by the IDEEA and diary classifications (75.6 ± 10.4%, 74.8 ± 9.7%, and 72.2 ± 10.3%; p<0.05). In conclusion, cross-validation of training data overestimates the accuracy of the classification algorithms in daily life.

Prolonged sitting is a potential health risk, not only for people with an inactive lifestyle, but also for those who do meet the recommended amount of physical activity. In this paper, we present two waysto promote the reduction of sedentary behavior. First, we report onan experiment in which office workers (n = 40) received timely persuasive messages on their smartphones, advising them to take an active break whenever 30 minutes of almost uninterrupted computer activity was recorded. The messages resulted in a significant decrease in computer activity and a peak in physical activity, indicating that participants complied to the given advice and took short breaks upon receiving a message. Second, we developed SitCoach, a mobile application to nudge office workers from their seats. SitCoach monitors physical activity and sedentary behavior to provide timely feedback by means of suggested sitting breaks. The results of a user test showedthat the general awareness of the importance of sitting breaks is low. In addition, the ability to take sitting breaks was considered to be highly dependent on external factors. This suggests that raising awareness and increasing self-efficacy are important prerequisitesfor a successful intervention to reduce sedentary behavior.