Four Movement Screen Structure (4MS): A Theoretical Framework for Understanding Postural Control Structures Underlying Activities of Daily Living and an Exploratory Cross-Sectional Study

BackgroundActivities of Daily Living (ADL) assessments are essential outcome measures in rehabilitation and long-term care, but primarily focus on task completion and provide limited insight into the postural control structures underlying movement failure. This paper proposes the Four Movement Screen Structure (4MS), a theoretical framework that reconceptualizes human movement control through four postural control phases: supine, sitting, standing, and single-leg standing. The framework proposes that functional decline may present with non-continuity, asymmetry, and compensatory preservation, rather than a simple reversal of motor development. MethodsAn exploratory, hypothesis-generating cross-sectional study was conducted with 297 certified care recipients (mean age 80.5 years) across multiple day-service facilities in Japan. Each participant was assessed using both the Barthel Index (BI) and the 4MS evaluation. Descriptive statistics, Pearson correlations, chi-square tests, and Fishers exact tests were used to explore the structural properties of the framework. ResultsThe mean BI total was 89.0 (SD = 13.8); the mean 4MS total score was 7.75 (SD = 2.02). A moderate positive correlation was found between BI total and 4MS total score (r = 0.471, p < 0.001, 95% CI [0.378, 0.555]). Of the five defined decline types, four were observed: mixed (57.6%), supine-dominant (21.2%), standing-dominant (5.7%), and single-leg-dominant (15.5%); sitting-dominant was not observed. The supine phase was the primary intervention target in 74.4% of cases--a finding we term the "supine paradox." In a subsample of 274 participants, 90.0% of those in the low supine score group (0-1.0, n = 170) performed rising from supine independently, suggesting that this paradox reflects qualitative deficits in foundational motor control masked by compensatory strategies. ConclusionsThese exploratory findings are broadly consistent with the non-reversal hypothesis and suggest that 4MS may capture structural dimensions of postural control not fully represented by conventional ADL assessment. As a hypothesis-generating study, these findings should be interpreted as generating testable hypotheses for future longitudinal and interventional research. Keywords: Postural control; Activities of daily living; Motor development; Functional decline; Barthel Index; Long-term care; Supine paradox; Non-reversal hypothesis; Geriatric assessment; Exploratory study