Background Family physical activity (PA) promotion holds promise, but there is little high quality research evaluating its potential and impact. Following successful feasibility assessment and adaption, this pilot study assessed the acceptability of FRESH, a child-led family-based PA intervention delivered online, and explored preliminary effectiveness.

Methods In a three-armed pilot randomised controlled trial (prospectively registered: ISRCTN12789422), 41 families (with 7–11-year-old index child) were allocated to a standard care control (CON), ‘pedometer’ (PED), or ‘family’ (FAM) group of the Self-Determination Theory-guided FRESH intervention. All family members in PED and FAM received pedometers and generic walking information; FAM additionally received access to the FRESH website, enabling participants to select step challenges, log steps, and track progress as they virtually globetrotted. All family members were eligible to participate; follow-up occurred 8-weeks and 52-weeks post-baseline. During home visits, research assistants assessed physical (e.g., fitness), psychosocial (e.g., social support), and behavioural (e.g., device-measured family PA) measures. Process evaluation questionnaires assessed acceptability of the intervention and accompanying evaluation. Semi-structured focus groups were conducted and website engagement explored.

Results Of 41 families recruited (149 participants; 4.0±1.0 (mean±SD) people/family), 40 (98%) and 36 (88%) were retained at 8-week and 52-weeks follow-up, respectively. Compared to CON and PED, a greater percentage of FAM children self-reported doing more family PA (CON: 35%, PED: 45%, FAM: 83%) and found FRESH fun (CON: 93%, PED: 81%, FAM: 94%). Higher mean (±SD) scores were reported by parents in FAM for improved PA awareness (3.6±0.6 vs. 3.2±0.7) and increased family PA (3.0±0.8 vs. 2.5±0.8) compared to PED. Approximately 82% of FAM children wanted to keep using the FRESH website and 93% found it easy to use. Focus groups revealed FAM families enjoyed choosing weekly step challenges and were capable of identifying ways of meeting daily steps goals. In children, there were no notable between-group differences found for change in minutes in moderate-to-vigorous PA (MVPA) at 8 or 52 weeks. In contrast, change in MVPA minutes differed between adults in the FAM group and those in PED or CON groups (FAM vs CON: 9.4 [95%CI: 0.4, 18.4]; FAM vs PED: 15.3 [95%CI: 6.0, 24.5]; PED vs CON: -5.8 [95%CI: -15.1, 3.3]), however this was not maintained at 52-weeks.

Conclusion Preliminary process evaluation findings related to the FRESH intervention and evaluation were promising, particularly amongst FAM participants. Preliminary effectiveness indicates potential changes in adults, but not in children, warranting further investigation.