The Ability to Relax Muscles in Chronic Pain Conditions in the General Population: A Cross-Sectional Study (The HUNT...

Muscle tension is considered a central pain mechanism in some chronic pain conditions. In clinical practice, muscle tension can be examined as the ability to relax through tests for flexibility and passive movements. However, empirical evidence for the association with chronic pain is limited. We aimed to investigate and compare the ability to relax muscles in individuals with and without chronic pain and to particularly study individuals with Fibromyalgia syndrome (FMS) and Chronic tension-type headache (CTTH) compared to other chronic pain conditions.

We utilized data from the HUNT Pain Examination Study, which included 551 individuals from the general population of Norway. These participants underwent clinical assessments by experienced physicians and physiotherapists to identify chronic pain conditions, and 399 were diagnosed with chronic pain of at least moderate severity, including 57 with FMS and 23 with CTTH as their primary diagnosis. The Global Physiotherapy Examination, which includes tests for flexibility and passive movements, was used to assess the ability to relax muscles. Associations were investigated using multiple linear regression analyses, first with chronic pain as the independent variable in the total sample and then with FMS and CTTH, respectively, in analyses restricted to those with chronic pain.

Compared with those with minimal or no chronic pain, participants with moderate to severe chronic pain had significantly reduced ability to relax muscles in terms of both flexibility and passive movements. Further reductions in flexibility and passive movement were found in those with FMS and CTTH compared with other chronic pain conditions.

This study demonstrates a reduced ability to relax muscles in individuals with chronic pain, particularly those with FMS or CTTH, suggesting a mechanism through which relaxation techniques could benefit these groups.