Muscle fatigue in early fibromyalgia

Area of Science:

• Exercise Physiology
• Neurology
• Rheumatology

Background:

• Fibromyalgia (FM) is a chronic condition characterized by widespread pain and fatigue.
• Understanding muscle fatigue mechanisms in FM is crucial for effective management.
• Previous research suggests altered physiological responses in FM patients during exercise.

Purpose of the Study:

• To compare muscle fatigue processes in fibromyalgia patients with healthy individuals during prolonged exercise.
• To investigate the physiological responses, including muscle force, electrophysiology, and biochemical markers, during fatiguing exercise in FM.

Main Methods:

• Nine female fibromyalgia patients performed repetitive isometric quadriceps contractions until exhaustion.
• Measurements included maximal voluntary contraction (MVC) force, electrically stimulated tetanic forces, electromyography (EMG), plasma catecholamines, blood lactate, plasma potassium (K+), heart rate, and VO2.
• Exercise involved 6-second contractions at 30% MVC with 4-second rest intervals.

Main Results:

• Muscle fatigue in FM patients showed a parallel decline in MVC and stimulated forces, suggesting no central fatigue.
• Muscle relaxation rate increased, and EMG amplitude during contractions rose, consistent with healthy individuals.
• Plasma catecholamines remained unchanged, while blood lactate and plasma K+ showed a modest increase; pain was reported.

Conclusions:

• Fibromyalgia patients demonstrate physiological muscle fatigue responses comparable to healthy individuals.
• A key difference observed was the absence of an increase in plasma catecholamine concentrations during exercise in FM patients.
• These findings contribute to understanding the specific physiological adaptations to exercise in fibromyalgia.