A Descriptive Hierarchical Approach to Analyse Activities Through Causal Mechanistic View

Abstract

Activities of Daily Living (ADLs) are essential routines that support individuals’ independence and well-being. For people with upper limb impairments, limitations in hand and arm function can make performing ADLs challenging. Therefore, interventions such as prostheses or rehabilitation therapies must be designed to restore or support these functions, with ADLs serving as meaningful outcome measures to assess their effectiveness. This study presents a user-centered framework for aligning the residual abilities of upper limb prosthesis users with the motion demands of ADLs. Activities were decomposed into tasks and elemental tasks to be executed sequentially to establish a two-way relationship between required movements and user capabilities. The goal was to identify which abilities are essential for specific tasks and how these maps to successful activity execution. An experimental study was conducted with ten healthy participants performing 36 variants of drinking and pouring activities to develop and validate the framework. These activities were ana- lyzed in real and structured home-like environments using an in-house Digital Human Model and a motion capture system. The object interactions with participants’ upper body movements are tracked to determine joint motion ranges, task constraints, and required exertion. Data collected helped analyze the relationship between object conditions, motion demands, and user abilities. Results highlight the complexity of predicting activity success, as users often compensate for limited abilities in varied ways. The tasks are described in terms of force and range of motion that improved the feasibility of prediction; binary success/failure outcomes were limited by indi- viduals’ diverse movement strategies and additional degrees of freedom. Nonetheless, identifying compensatory strategies helped clarify how individuals adapt to meet task demands. The findings reinforce the importance of integrating ADL motion requirements into the de- sign of upper limb interventions. By systematically mapping abilities to activity components, this research enables more targeted and personalized rehabilitation strategies, ultimately reducing abandonment rates and enhancing user autonomy. The object-centric, task-based approach offers a robust framework for evaluating intervention performance and guiding future design efforts in interventions and rehabilitation.