Researchers Use Exercise to Illuminate How You Feel
What if a blood test could reveal the muscle fatigue, pain and exhaustion that you feel? This may seem like a pipe dream, but a husband and wife team at the University of Utah (Alan Light, Ph.D., and Kathleen Light, Ph.D.) just published very encouraging preliminary findings and are now working to refine their biomarker techniques.*
One of the key elements of the Lights’ studies involves looking at what happens when people with chronic fatigue syndrome (CFS) and fibromyalgia exercise. During and after exertion is when CFS and fibromyalgia patients say they feel the worst, which is why the Lights are capturing blood samples up to 48 hours after a standard exercise routine. Healthy people, however, usually find a bout of exercise to be invigorating, and it pours out substances that reduce painful sensations.
The symptoms in up to 70 percent of fibromyalgia and CFS patients overlap, and both conditions are defined by symptoms, which makes their diagnosis and treatment all the more difficult. Patients also face serious credibility issues in the doctor’s office when their symptom severity cannot be documented anywhere in their blood work or other standard tests. Without disease biomarkers, it is hard to be a patient with fibromyalgia or CFS, but there is good reason to believe this gloomy picture is going to change.
Your muscles have a system to sense fatigue, just as they are capable of sensing pain. It is all based on the metabolic or chemical byproducts made in your muscles. The more you work your muscles, the greater the accumulation of metabolic substances that can stick around to activate the pain and fatigue detectors. Healthy people and CFS and fibromyalgia patients have these same detectors in their muscles. Perhaps exercise may cause more to be produced, or they might be more easily activated in CFS and fibromyalgia patients. These are questions that the Lights sorted out in their preliminary study of 19 CFS patients (13 of them meeting the diagnosis for fibromyalgia) and 15 control subjects.
The detection system that initially signals “fatigue” in exercising muscles and later picks up “pain” actually involves four different chemical receptors. In addition, there are sensory receptors used by your peripheral nervous system and various substances released by your immune system, all of which may combine to set off alarms of pain and fatigue in your muscles.
Prior to exercise, the levels of the various sensory receptors and immune substances were similar between the fibromyalgia and CFS patients and healthy controls. This finding alone explains why everything looks so “normal” with your blood work and could also be the reason why other research teams have not been able to find significant abnormalities in your blood. However, after 25 minutes of moderate (not maximal) exercise, differences between the patients and controls were dramatic.
“Thirty minutes after exercise, we were seeing substantial increases in all of these receptors,” says Dr. Alan Light. The healthy controls showed little change throughout the 48-hour test period. Referring to the receptor activations in the CFS patients, Light adds, “At 48 hours, they are barely just starting to go down.”
The Lights identified multiple sensory receptors that increased two to eight times their resting values in the CFS patient group. Many of the immune substances and receptors used by the peripheral nervous system (such as the adrenergic receptors) were also greatly elevated by the exercise routine. In comparison, little to no activity occurred with any of these receptors or substances in the healthy subjects.
Elevation of certain sensory receptors and immune substances were more likely to be correlated with fatigue while others were more likely to be associated with symptoms of pain. The Lights point out that there may be several subgroups of CFS and fibromyalgia, which makes sense because not all patients respond in the same fashion to medications. But “a simple blood test that provides an objective measure for excessive and debilitating fatigue would be diagnostically valuable to physicians and patients with CFS.” Being able to tease out the different subtypes and offer an objective measure of widespread muscular pain for fibromyalgia patients would truly be an asset.
Now that the Lights have published the groundwork on a small group of CFS patients, with 70 percent meeting the criteria for fibromyalgia, they are moving on to refining their tests with the goal of generating biomarkers for these two conditions. The CFIDS Association of America is funding the expansion on CFS patients while the American Fibromyalgia Syndrome Association is funding the expansion on fibromyalgia. The goal is to turn this preliminary work into test markers that validate how severely impacted you are by your symptoms and to give researchers a guidepost for testing the effectiveness of new medications.
* Light AR, et al. J Pain July 31, 2009 [Epub ahead of print].