The authors explain how SCEDs can provide rigorous evidence about intervention effectiveness using repeated measurements from one or a small number of participants. By allowing individuals to act as their own controls, SCEDs are particularly useful for rare conditions, highly individualised interventions, and clinical settings where large-scale trials are impractical. The paper outlines different SCED methodologies, key design considerations, outcome measurement strategies, and approaches to data analysis. Overall, it presents SCEDs as a valuable methodological tool that bridges clinical practice and research while supporting evidence-based rehabilitation.