Short-term effects of a trunk modification program on patellofemoral joint stress in asymptomatic runners

Objectives: To evaluate short-term effects of a four-week gait retraining program using visual feedback on trunk flexion angle, patellofemoral joint (PFJ) stress, lower extremity biomechanics and motor skill automaticity.

Design: Longitudinal interventional study.

Settings: University research laboratory.

Participants: Twelve asymptomatic recreational runners (seven male and five female).

Main outcome measures: Trunk kinematics as well as lower extremity kinematics and kinetics were assessed prior to training at week 1 (baseline) and week 2, 3, 4 and 8 (retention). PFJ stress was computed using a sagittal plane model. A dual-task procedure was performed to examine automaticity.

Results: At week 8, runners demonstrated 10.1° increase in trunk flexion angle (p < .001) and 17.8% reduction in peak PFJ stress (p < .001) compared to baseline. This is associated with a 16.8% decrease in knee extensor moment and less than 2.5° change in knee flexion angle. Participants also showed 33.3% increase in peak hip extensor moment and small reduction in peak ankle plantar flexor moment. Lastly, runners demonstrated automaticity of the modified skill with a dual-task cost of less than 3%.

Conclusion: The gait retraining program is effective to elicit short term changes in trunk position, PFJ stress, and automaticity of the new motor skill.