Biomechanical characteristics of lumbar manipulation performed by expert, resident, and student physical therapists

Lumbar manipulation is a commonly used treatment for low back pain, but little research evidence exists regarding practitioner biomechanics during manipulation. Most existing evidence describes rate of force production through the hands into instrumented manikins and it is unclear how the practitioner moves their body and legs to generate this force. To identify and characterize important kinetic and kinematic factors in practitioners of varying experience performing lumbar manipulation in order to identify which factors distinguish experts from less experienced practitioners. This was a cohort observational laboratory study. 43 male physical therapists (PT) and PT students (4 experts, 11 residents, 13 third year, and 15 first year students) performed 4 manipulations each on asymptomatic patient models. Angular and linear kinematics of the pelvis were measured using motion capture, and ground reaction forces were measured with force plates under the practitioner's feet. Peak pelvic angular velocity was greater and in the opposite direction in experts compared to other groups in the frontal plane (p = 0.020) and transverse plane (p = 0.000). Experts had greater downward pelvic linear velocity than third year students and first year students (p = 0.000). Experts also demonstrated faster rate of vertical ground reaction force unloading during the manipulation (p = 0.002). Expert performance of manipulation was characterized by increased speed of linear and angular pelvic motion, and increased modulation of vertical ground reaction force. These results help to inform educators and practitioners that teach and use this complex manual skill. •Operator mechanics of lumbar manipulation (SLM) are not well understood.•Experts rotate their pelvis in the opposite direction during SLM.•Experts perform SLM with greater downward pelvic velocity.•Pelvic velocity can be predicted though years of experience, among other factors.