Contribution of Load Expectations to Neuromechanical Adaptations During a Freestyle Lifting Task: A Pilot Study

Objectives: The main goal of this study was to determine to what extent load expectations modulate neuromechanical adaptations in individuals with and without chronic low back pain (cLBP) when lifting and lowering various loads. The second goal was to assess the feasibility of a simple lifting protocol during which expectations about loads were manipulated. Methods: Seventeen participants with cLBP and 18 participants without low back pain were asked to lift and lower boxes of mild to moderate loads. Two kinds of expectations (lighter and heavier) were respectively associated to each experimental block. Self-reported exertion was assessed to control for expectations modulation. Erector spinae and vastus lateralis electromyography (EMG) activity were recorded and kinematics angle calculated. Results: The results showed a main effect of expectations, with loads introduced as heavier being associated to a higher exertion compared with loads introduced as lighter. EMG activity analyses revealed significant interaction involving expectations, movement phase, and loads, as well as significant differences between groups. Kinematic angles did not reveal any significant effect of expectations nor group during the lifting phase. Conclusions: Psychological factors may contribute to neuromechanical adaptations to low back pain. Our preliminary findings show that expectations about loads may result in neuromechanical differences between individuals with cLBP and those without cLBP. This pilot study showed that testing the manipulation of expectations and EMG records was feasible but highlighted the need to go beyond single infrared markers to assess kinematics.