Moving Together, Aging Better: Wearable-Measured Physical Activity and Social Interaction in Older Adults' Community Dance Sessions

Community dance is the most common structured physical activity taken up by older women in China, and at least eight controlled and cohort studies have recorded its health effects. Exposure in nearly all of this work is measured by questionnaire, however, which cannot separate ninety minutes of continuous stepping from forty minutes of stepping broken up by instruction, standing and conversation. If social interaction is the ingredient that makes communal dance different from walking, what matters is not weekly minutes but the events that occur inside the session. The protocol describes a three-clock measurement design. Hip-worn accelerometry at 60-second epochs, 15-second GPS fixes within a 60-metre session geofence, and 30-second momentary observation of the same sessions by two coders are aligned on one common time base. Session-level observations, estimated at 800 to 1,150 person-sessions, will be linked to seven-day free-living activity in 96 dancers from eight squads and 40 older adults who walk alone. Social interaction is operationalised as interaction density, the share of observed intervals containing either a verbal exchange or a group response to a leader's instruction. The planned analyses cover compositional analysis of sedentary, light and moderate-to-vigorous behaviour; isotemporal substitution of 30 minutes of sedentary time with session moderate-to-vigorous activity; mixed models with participant and squad random intercepts and within-person centring of interaction density; and bootstrap mediation of the association between session activity and loneliness through interaction density. The design aims to establish whether the health advantage of communal dance over solitary walking is carried by the social structure of the session rather than by its activity volume, and to produce a session-level metric that public health programmes can specify, audit and reproduce.