Motor-evoked pain on a background of widespread muscle strain: a novel model simulating everyday activities.

OBJECTIVES

Musculoskeletal pain is among the most prevalent types of pain. However, experimental models that induce acute musculoskeletal pain by everyday activities - on top of sustained daily muscular strain - in a controlled and moderate manner are still lacking. Such models are essential for investigating underlying mechanisms of musculoskeletal pain and evaluating treatment approaches. The present study proposes a novel experimental model to address this gap.

METHODS

A total of 43 pain-free participants completed two motor (lifting objects) and two sensory (hot water immersion, noxious pressure) pain challenges. Participants were randomly assigned to either an experimental group, who wore a suit that induced widespread muscle strain through limb weights and joint restrictions, or a control group without the suit. Both groups performed the additional pain challenges. Numerical pain ratings, pain-related facial expressions (Facial Action Coding System, FACS), heart rate (HR) and its variability (HRV), as well as electrodermal activity (EDA), were recorded.

RESULTS

Wearing the experimental suit to induce muscle strain led to increased pain ratings during motor challenges when further muscle power was required (weightlifting). Additionally, pain-specific facial responses and autonomic markers (heart rate and tonic EDA) were significantly elevated in the experimental group during motor tasks. No significant group differences were observed during the sensory pain challenges.

CONCLUSION

This study introduces a novel and effective experimental model for inducing acute musculoskeletal pain by applying light weightlifting on top of sustained muscular strain, with both stressors designed to reflect everyday motor activities. This approach offers a promising tool for future research into pain-relieving interventions and the mechanisms of musculoskeletal pain, including studies involving affected patient populations.