Hyperthermia in Patients With Chronic Primary Pain - Effects on Thermoregulation, Somatosensory System and Movement Evoked Pain

This study, in a quasi-experimental matched two-group pre-post design, investigates the effect of serial water-filtered whole-body hyperthermia on circadian core body temperature, the somatosensory system (nociception) and the movement evoked pain in healthy and patients with chronic primary pain (e.g., fibromyalgia). The intervention lasts 3 weeks with two treatment sessions per week.

Inclusion Criteria: patients: * Confirmed diagnosis of widespread pain (ICD-11 MG30.01) * Widespread Pain Index (WPI) ≥ 7 and Symptom Severity (SS) scale ≥ 5 or WPI) ≥ 3 and SS ≥ 9, * Pain \>= 3 month and VAS \>= 4,0 * Body - infrared-A-Bulb Distance \< 38cm (overweight participants) * Signed declaration of consent healthy: * No chronic illnesses * No acute infections * No regular medication: To avoid interactions * BMI ≤ 40kg/cm2 * Mental health: No psychiatric diagnoses or psychotropic medication in your medical history Exclusion Criteria: * Participation in other clinical studies * Contraindications for hyperthermia (severe cardiovascular diseases, tumour diseases, acute infections, pregnant and breastfeeding women) * Acute and / or feverish microbial infections * Participants with severe somatic, rheumatic concomitant endocrine or neurological diseases, in particular neurological diseases associated with cognitive disorders, severe liver or kidney and cardiac diseases * participants who are permanently treated with opioids, cannabis, immunosuppressive drugs (e.g. corticoids, immunosuppressants) or alpha/beta-A(nta)gonists due to a disease from the group described above * participants with pain due to a serious psychiatric illness (bipolar disorder, psychosis, personality disorder, severe depression, substance abuse) and serious systemic or neurological disorders * pregnancy or breastfeeding (for women) * Intake of medication within 6 weeks that inhibits the reuptake of the neurotransmitter serotonin or binds to receptors of this neurotransmitter group