Title: A novel experimental model of Task-Relevant Low Back Pain (TRLBP)
Funder: Versus Arthritis

Abstract: The development of experimental pain models to gain insight into how nociception affects movement is crucial if we are to alleviate the burden on those who suffer with arthritis and other musculoskeletal disorders. In most experimental studies, pain is induced by injecting substances that create constant pain for a short duration. This model fails to capture temporal features of pain: for instance, pain intensity cannot be modulated depending on the motor behaviour adopted to perform a task – as happens in chronic musculoskeletal pain conditions. A few studies have attempted to replicate the temporal aspects of pain by delivering electrical painful stimuli during specific phases of a movement. However, habituation to the painful stimulus and the impossibility to investigate neuromuscular activation strategies using electromyography (EMG) due to stimulation artefacts, limits the validity of this model. This project will uniquely exploit recent advances in the use of sinusoidal waveforms to overcome the limitations of traditional electrical painful stimulation models, and will develop an experimental model that reproduces key features of clinical low back pain (LBP), including temporal characteristics of pain. Our protocol will use sinusoidal electrical painful stimulation to: i) induce pain with spatial characteristics similar to conventional square waves; ii) reduce habituation over time compared to conventional square waves and iii) allow EMG signals to be acquired without stimulation artefacts. This will lead to a task-dependent experimental pain model, where the pain intensity is modulated in real-time proportionally to the participant’s muscle activation. Healthy, pain-free participants will be recruited for all studies. In the first study (40 participants), an extensive methodological investigation will define how electrode position and stimulation waveform influence location, depth, and quality of the induced LBP, while ensuring the absence of stimulation artefacts or involuntary muscle contractions. In a second study, a further 40 participants will be exposed to continuous painful stimulation for 30 minutes to test habituation; and quantitative sensory testing will detect whether this protocol can induce sensitization. In a third study, 30 participants will be asked to perform a computer task in a sitting position for 2 hours while exposed to task-relevant painful low back stimulation. The stimulation intensity will be proportional to the activation of their erector spinae muscle. Changes in kinematics and whole-body reaction forces will be monitored to describe individual motor adaptations to the task-relevant painful stimulation. This project falls squarely within the ‘Understanding complexity: developing new experimental pain models’ mandate of the 2019 Pain Roadmap of Versus Arthritis. LBP is specifically mentioned in the award call. This novel experimental model will provide unique information on how people adapt to task-relevant pain. The extensive validation that we propose will be the foundation for future studies investigating sensorimotor adaptation in different musculoskeletal conditions of interest to Versus Arthritis. As the mechanistic information obtained with this model will be used to inform precision rehabilitation of spinal pain and other musculoskeletal conditions, it is expected that this project will contribute to the overall health of people with musculoskeletal disorders in the long term.


Research activity codes: 2.1 BIOLOGICAL AND ENDOGENOUS FACTORS;8.4 RESEARCH DESIGN AND METHODOLOGIES (HEALTH SERVICES)
Health categories: INFLAMMATORY AND IMMUNE SYSTEM;MUSCULOSKELETAL