Motor adaptations to movement-evoked low back pain

Devecchi, Valter (2024). Motor adaptations to movement-evoked low back pain. University of Birmingham. Ph.D.

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Abstract

Low back pain (LBP) is a main cause of disability worldwide, resulting in a significant socio-economic burden on society. In some people with LBP, the main mechanism of pain is nociceptive, and symptoms are increased by mechanical stimuli. By changing mechanical stresses applied to lumbar structures, movement and physical activity can exacerbate LBP, a phenomenon known as movement-evoked pain (MEP). Given the relationship between LBP and movement for many people, research has focused on how they influence each other with evidence supporting that people with LBP move differently. However, findings are often contradictory due to clinical heterogeneity. For this reason, experimental pain models have been used to better understand the effects of pain in the lumbar region on movement. Despite being clinically relevant, the investigation of MEP and its effect on motor adaptations remains underexplored in both experimental and clinical LBP. Understanding how movement-evoked LBP affects movement is essential as it could help to partially explain the clinical heterogeneity and mechanisms underpinning motor adaptations to pain, ultimately facilitating more personalised interventions for people with LBP. The primary aim of this thesis was to investigate how movement-evoked LBP affects how people move. Additionally, this thesis aimed to determine if such motor adaptations are specific to the direction of the pain provocative movement, and if they represent a purposeful strategy to reduce pain in accordance with contemporary theory on motor adaptation to pain. The first study within this thesis was a systematic review which supported the causal effect of pain experimentally induced in the lumbar region on motor adaptations, specifically revealing a reduction of the range of motion of the lumbar spine, reduced activation of deep trunk muscles, and task-dependent increased or decreased activation of superficial lumbar muscles. The systematic review revealed that the investigation of the effects of MEP was limited, as one study out of twenty-six used an experimental model where pain was modulated by movement. The second study of this thesis investigated the effects of MEP experimentally induced in the lumbar region in association to either lumbar flexion or extension. This revealed that MEP is a main determinant of motor adaptations to experimental pain since a reduction of lumbar movement was only observed in the pain-provoking direction. Also, participants who showed larger reductions of lumbar range of motion also reported lower pain intensity, supporting the notion that motor adaptations to experimental pain represent a purposeful strategy to reduce pain. The third study investigated motor adaptations to movement-evoked LBP in people with clinical LBP. Kinematic differences were specific to what trunk movement was pain provocative, with larger lumbar flexion and smaller knee and hip flexion seen for people reporting higher pain intensity during forward bending. Overall, this thesis showed that clinical and experimental pain in the lumbar region changes movement, and that the pain provocative direction is a main determinant of the observed motor adaptations. These results also confirm that motor adaptations are purposeful strategies to reduce pain. Pain directionality may explain some of that heterogeneity of motor adaptations observed in people with clinical and experimental LBP, and it may offer new insights for the development of personalised and more effective interventions for people with clinical LBP.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):