Isometric Exercise and Endogenous Pain Inhibition

The purpose of this study is to identify the acute effects of isometric exercise on the inhibition of pain in individuals with fibromyalgia.

Fibromyalgia syndrome (FMS) is a chronic pain condition that is characterized by widespread pain which affects 5-8% of the general population. Past research has shown that people with FMS demonstrate enhanced pain facilitation and reduced pain inhibition in the central nervous system. Incorporating a biopsychosocial model of pain may help develop strategies to prevent the functional decline and alleviate the suffering that occurs in this population. Exercise is a mainstay of pain rehabilitation with multiple health benefits, one of which is decreasing pain; a phenomenon known as exercise induced hypoalgesia (EIH). Emerging evidence has shown that exercise decreases pain facilitation in healthy adults and in some individuals with FMS. However, it's unclear whether exercise improves pain inhibition in individuals with FMS. The purpose of this study is to investigate endogenous pain inhibition, measured by conditioned pain modulation (CPM), following isometric exercise of the quadriceps muscle in individuals with FMS. In addition, factors that might affect this response such as physical activity, body composition, and psychosocial issues will be examined. Understanding how exercise impacts pain and the contributing factors will help guide the prescription of exercise to optimize pain rehabilitation.

The two groups will participate in two sessions receiving intervention or no intervention in a randomized manner.

Participants will perform a submaximal voluntary contraction of the quadriceps muscle to task failure.

Participants will be asked to hold a submaximal voluntary contraction of the quadriceps muscle as long as they can (task failure).

the change in pressure pain threshold (kPa) during or after the immersion of the foot in a cold water bath (approximately 6 degrees) compared with baseline (before foot submersion) constitutes the measure of conditioned pain modulation in this study.

a biothesiometer will be used to measure sense of vibration (threshold) local and distal from the exercising muscle.

in both sessions, pain intensity will be evaluated during ice water bath immersion (i.e. before and after exercise or quiet rest) and during exercise using an 11-point NPRS with 0 being no pain and 10 worst pain possible.

Inclusion Criteria: Men and women aged 18-75 diagnosed with fibromyalgia or healthy controls will be included in the study. Exclusion Criteria: cardiovascular disease, cancer, pregnancy, arthritis, diabetes, claustrophobia, Reynaud's disease, osteoporosis, neuropathy.