Increased trapezius pain sensitivity is not associated with increased tissue hardness

Area of Science:

• Musculoskeletal pain research
• Biomedical engineering
• Clinical assessment techniques

Background:

• Fatiguing exercise impacts muscle pain sensitivity and hardness, relevant to neck and shoulder pain.
• Objective assessment of muscle pain sensitivity is crucial due to the poor reliability of manual methods.
• Understanding muscle characteristics is key for managing work-related musculoskeletal disorders.

Purpose of the Study:

• To compare tender points identified by manual palpation with pressure algometry and hardness assessments.
• To investigate the effects of exercise on muscle pain sensitivity and hardness in the upper trapezius.
• To evaluate the coexistence and distribution of pain sensitivity and muscle hardness.

Main Methods:

• Assessed pressure pain thresholds and muscle hardness using computer-controlled pressure algometry.
• Manually palpated for tender points in 14 sites of the upper trapezius muscle in 12 healthy subjects.
• Measurements were taken at baseline, immediately after, and 20 minutes post-exercise (static or dynamic).

Main Results:

• A heterogeneous distribution of pressure pain sensitivity and muscle hardness was observed in the upper trapezius.
• Sites with low pressure pain thresholds (high sensitivity) were typically the least hard.
• Manually detected tender points did not always align with the most sensitive sites identified by algometry (29% discrepancy).

Conclusions:

• Clinical findings of heterogeneity in upper trapezius pain sensitivity and hardness are confirmed.
• Objective techniques for identifying tender points are important, but manual palpation is currently the best clinical practice.
• Short-duration, exhaustive exercise did not alter muscle sensitivity or hardness in asymptomatic muscles.