How and Why Snacktivity Supports Physical Activity Engagement in Adults With Chronic Low Back Pain: A Realist Review

Background Physical activity is a recommended first‑line treatment for the management of chronic low back pain, yet adherence to structured exercise often remains poor due to pain, fear, fatigue, and contextual barriers. Snacktivity™, which promotes brief, frequent bouts of movement embedded in daily routines, has emerged as a potentially feasible alternative. However, it remains unclear how, why, and for whom Snacktivity supports engagement in physical activity for people living with chronic low back pain. Objective To develop and refine programme theories explaining how Snacktivity‑type interventions support physical activity engagement and related outcomes in adults with chronic low back pain. Methods A realist review was conducted following RAMESES standards. Initial programme theories were developed and iteratively refined through synthesis of quantitative, qualitative, and mixed‑methods evidence from Snacktivity and related sedentary‑reduction interventions in low back pain and other adult populations in order to test developed programme theories. Evidence was analysed to identify context–mechanism–outcome configurations. Results A total of four studies met the inclusion criteria for Snacktivity-type studies related to low back pain and were included to develop and test the initial programme theories. This was supported by 38 studies that contributed evidence to programme theory refinement. Five refined programme theories were supported. Snacktivity appears to enable engagement by lowering perceived burden and threat rather than eliminating fear, generating mastery experiences that enhance self‑efficacy, and reducing symptom interference through brief, distributed activity. Education and coaching components supported meaning‑making by reframing movement as legitimate and achievable, while environmental cues and routines promoted habit formation. Psychosocial outcomes (confidence, mood, vitality) and habit formation improved more consistently than performance‑based outcomes, and engagement was sustained even when pain or fatigue persisted. ConclusionsSnacktivity functions as a participation‑enabling intervention rather than a traditional exercise prescription. Its effectiveness in chronic low back pain is explained by psychosocial and contextual mechanisms that support psychological safety, mastery, and habit formation. These findings support a shift from dose‑response exercise models toward interventions that prioritise feasibility, meaning, and sustained participation in daily life.