. GymSkill: automated assessment for balance board training
With GymSkill [24,25], we present a smartphone application that addresses the shortcomings described above and
introduces individualized exercise skill assessment fully based on integrated sensors. We describe the iterative design
process, qualitative user feedback and quantitative validation of our assessment algorithm.
3.1. Balance board training
We chose balance board training as a representative discipline for physical exercising support, applicable to a wide range
of young and old users, both for fitness training and rehabilitation [26,27]. With help of a sports medicine specialist, a set of
20 exercises was conceived and fed into the GymSkill application.
3.2. The GymSkill application
GymSkill is implemented as an Android application and consists of an exercise database, sensor data recorder and the skill
assessment presentation (see Fig. 3). During the performance, the smartphone (app running) is placed on top of the balance
board (see Fig. 1) so that it can record all of its movements. The user begins her training by selecting an individual exercise or a
complete training plan (see Fig. 4). Each exercise is explained step by step in text and pictures. During the actual performance,
the phone records accelerometer and magnetometer data as a basis for the assessment which is presented to the user after
completion of each exercise. GymSkill is freely available in Google Play as a research app under the name ‘GymSkill’.