The effects of combined action observation and motor imagery (AO + MI) practice on motor learning: a systematic review

Behavioural research indicates that motor learning can be enhanced using combined action observation and motor imagery (AO+MI) in healthy adults. Notable inconsistencies remain, however, across AO+MI study designs. Our aim was to systematically search major academic databases to evaluate AO+MI practice effects on motor learning in healthy adults (search completed March 2024). Eligible peer-reviewed studies included randomised and non-randomised controlled trials comparing AO+MI against AO, MI, or controls, written in English. AO+MI was delivered synchronously or asynchronously, with a physical post, retention, or transfer test. Studies involving physical practice during mental practice were excluded. Risk of bias was assessed using the Cochrane tool, and findings were narratively synthesised. Seventeen studies comprised 34 AO+MI groups across 10 tasks. Positive effects for AO+MI (n=422) were observed, compared to AO (n=99), MI (n=98), and controls (n=227), across tasks, modalities and training durations, and when mentally practised and physically executed actions differed. Limitations included inconsistent terminology, ill-defined interventions, and a lack of retention and transfer tests. While AO+MI represents a widely applicable practice augmentation for motor skill development, we recommend designing the right intervention for the right individual. Future research must curb the proliferation of terminology and refine intervention designs to support scientific progress.