Development and iterative optimization of an independently usable assistance system to assess, maintain and improve the nutritional and mobility status of older adults: an iterative usability study

Promoting a balanced diet and regular physical activity is crucial for maintaining independence in old age. Technical assistance systems can help identify nutritional and mobility deficits and initiate appropriate interventions. We are developing a technical assistance system consisting of a measurement and training station and a tablet-based app (AS-Tra). AS-Tra is specifically designed for independent use by participants aged ≥ 70 years to assess and improve their nutritional and mobility status. This study aimed to identify optimization potentials of the AS-Tra system together with members of the target group through iterative test cycles until good usability is achieved. The system is developed as a complex intervention in accordance with the Medical Research Council (MRC) framework and assessed in three iterative cycles for its usability. In each cycle, participants carried out structured predefined tasks. To capture their cognitive process, they were asked to ‘think aloud’. These thoughts were recorded with the necessary support for completing each task. Usability was measured using the System Usability Scale (SUS). Improvements based on the results were made. In the third cycle, independent use was simulated by leaving the participants alone in the lab, receiving tasks via audio instructions and observing them via webcams and eye-tracking glasses. A total of 34 participants (78.60 ± 5.59 years, 70.93% female) were included in the three iterative cycles (C1–C3). The SUS score improved from 70.63 to 84.55 between C1 and C2 and decreased slightly to 78.18 at C3. Overall 63.11% of the tasks (n = 385) were completed without support. In 14.92% (n = 91) of all tasks, the task could be completed by repeating or rephrasing instructions, 20.33% (n = 124) with direct reference to the solution, and 1.15% (n = 7) of all tasks could not be completed independently. The results of the cycles made it possible to develop an independently usable system for assessing the nutritional and mobility situations of older people with good usability. Additionally, the relevance of support functions and the importance of research under real conditions became clear. German Clinical Trials Register (DRKS), DRKS00031719, registered May 2023, https://drks.de/search/de/trial/DRKS00031719.