TABLE 2.

Primary outcome results: summary of usability protocol with supervisors’ observations and participants’ feedback.

Criteria	Positive aspects	Negative aspects
Functionality and interaction with the system	– Simple set up – Easy usable game composition	– Very specific movements/steps needed for step-based cognitive games (specific and strict step detecting algorithm) – Technical malfunctions of HDMI dongles
IMUs	– Comfortable to wear – Easy to attach (slap band) to wrists/ankles – Slap bands are easy to clean (e.g., from sweat) – Feasible navigation with the right hand IMU (“hand mouse”) – Battery can be easily charged	– Instable IMU connection (via Bluetooth) – Activation of the “hand mouse” in inappropriate situations (e.g., during dancing) – Suboptimal navigation for left-hander – Technical malfunctions of IMUs
Design	– Appealing game design – Pleasant and diverse music – Cute and funny cartoon-based instructor	– Virtual instructor could be more motivating (gestures as “thumps up”, comments etc.)
Training principles	– Real-time feedback while exercising (auditory and visual, positive and negative) – Performance score as feedback after exercising is motivating – High variability of exercises and levels	– Auditory feedback (sounds for “right” and “wrong”) could be louder in relation to background music – Feedback not always traceable – Partly inaccurate evaluation of movements
Exercises	– Clear structure of exercise levels – Entertaining quiz questions between strength exercises – Challenging strength and balance exercises (especially higher levels) – Exciting and challenging step-based cognitive games – Duration of the exercise is displayed – Helpful cues (arrows) to prepare the next movement	– Dance steps sometimes not perfectly instructed (difficult to reproduce) – Turns in dancing are difficult as no view on TV while turning – Instructions in English (difficult to understand for German-speaking participants) – Only frontal view of exercises (side view missing)
Emotions	– Motivation and fun (despite of technical malfunctions) – Curiosity about what is coming in the next levels – Happiness when seeing progress or achieving more performance points	– Frustration and displeasure because of technical issues and inaccurate evaluation of movements – Impatience with navigation

IMU, inertial measurement unit.