Lin et al. [11] examined stylus-based tapping behavior while walking in order to find out about the effects of walking on performance. Furthermore, they compared two different ways of simulating realistic walking and let their participants walk on a treadmill and on an obstacle course. Their results show that the usage of the obstacle course leads to more realistic results as the user has to perform the navigation and walking task in parallel to the target acquisition task. When analyzing the data, they saw that walking had no effect on the time needed to select a target, but they saw an increase towards overall task completion time, error rates and workload. Furthermore, they showed that participants reduced their walking speed in order to select the targets accurately. In addition, they analyzed the effect of different target size and their results show that error rate and selection time decrease the larger the target is. A key difference to our work, lays in the fact that in their study a stylus and therefore two handed interaction was analyzed. In our study, we considered one-handed interaction in which the user uses their thumb to select a target as this is currently the most commonly used technique with touch screen phones