Mechanistic Explanations of Manual Therapy Do Not Influence Outcomes in Healthy Individuals: A Randomized Controlled...

Manual therapy is widely applied for musculoskeletal dysfunction and pain, yet the mechanisms underlying its effects remain incompletely understood. Local biomechanical and central neurophysiological processes are considered relevant, while contextual factors such as patient expectations and therapist beliefs may further influence treatment outcomes. This study investigated whether suggestions regarding the mechanisms of manual therapy modulate treatment effects on range of motion (ROM) and pressure pain threshold (PPT), both locally and at a remote site.

Ninety-three healthy participants were randomized, in a university campus laboratory, to one of three groups, each receiving a distinct mechanistic suggestion (biomechanical, neurophysiological, or none) prior to a standardized lumbar manual therapy intervention. The outcomes comprised lumbar ROM, PPT, and movement-related pain, assessed before and after the intervention at the treated site and at a remote site, and analyzed using a general linear model (GLM).

All groups showed significant improvements in ROM over time (p = 0.01, η²_p = 0.07) and between assessment areas (p = 0.006, η²_p = 0.08). However, no main effect of group was detected (p = 0.40), and no significant two-way or three-way interactions emerged (all p > 0.05). Similarly, no between-group differences were observed for PPT or movement-related pain.

Suggestions regarding the mechanisms of manual therapy did not influence treatment outcomes in healthy individuals. Cognitive modulation through mechanistic suggestions failed to alter ROM, PPT, or movement-related pain.