Patients’ expectations are known to influence pain perception and treatment outcomes. These expectations are associated with different brain activity patterns in areas relevant for pain processing; therefore, the anticipation of pain relief or increase are related with actual pain reduction or increase.
Fifteen healthy subjects volunteered for the study. Pain was experimentally induced in the thenar muscles through a saline injection and patients were randomised to “muscle pain” or “nerve pain” groups.
Both groups received information about upper limb anatomy and the ULNT1 test (they were told that each position had a different degree of mechanical load applied to the nerve, and that the greater the load, the greater the pain). The “muscle pain” group was told that saline injections are a common experimental method to induce muscle pain, while the “nerve pain” group was told that saline injections cause pain by stimulating or irritating nerve receptors.