Does mental practice work? It does.
Those working in the field of imagery know well the meta-analysis authored by Driskell, Copper & Moran and published in 1994. Recently, Toth and colleages, and again together with Adain Moran, published their update after more than two decades of additional work in 2020 on imagery and its effects on performance.
Looking at the effects of imagery on various sports- and action-related outcomes, we just published a pre-print version of this piece of work (see here):
We performed a meta-analysis to extend the current understanding of the effectiveness of imagery in sports on any sport specific outcome and the relevance of third variables potentially moderating the effect. The overall effect of imagery interventions was medium in magnitude with d= 0.431 (95% CI [0.298, 0.563]). Imagery interventions significantly enhanced motor performance, motivational outcomes, and affective outcomes. Imagery combined with physical practice was more effective than physical practice alone, indicating differential effects of imagery and physical practice. Theeffectiveness of imagery was positively associated with the intensity of the imagery training.