Resistance exercise may improve pain, fatigue, and muscular strength in lean women with fibromyalgia (FM), according to a new study. In overweight and obese women, this type of exercise may improve arm strength.
The results were published in the journal BMC Musculoskeletal Disorders, titled “Benefits Of Resistance Exercise in Lean Women With Fibromyalgia: Involvement of IGF-1 and Leptin.”
FM is characterized by chronic pain and fatigue, although the exact mechanisms underlying these symptoms remain elusive. Obesity is also more common among FM patients (prevalence between 40-70%) and associated with increased levels of pain.
Previous studies have shown that FM symptoms may improve after aerobic exercise, which may involve metabolic factors such as insulin-like growth factor 1 (IGF-1; plays a key role in the adaptation to exercise) and leptin.
To investigate metabolic factors in relation to resistance exercise, the study (NCT01226784) enrolled 43 women with FM (ages 20–65) to participate in a program of supervised progressive resistance exercise, two times a week for 15 weeks. Blood samples were collected at the study’s start and end to analyze the levels of free and total IGF-1, IGF-binding protein 3 (IGFBP3), adiponectin (a protein that plays a role in insulin resistance), leptin (a hormone that regulates satiety and body weight), and resistin (a hormone that may be involved in obesity, insulin resistance, and diabetes).
Pain was assessed with a visual analogue scale; fatigue was rated using the multidimensional fatigue inventory (MFI-20), subscale General Fatigue (MFIGF). Knee extension force, elbow flexion force, and handgrip force were evaluated using dynamometers (devices that measure mechanical power and force).
Lean FM women (18 patients) had significantly lower levels of free IGF-1, IGFBP3, and leptin than overweight (17) and obese (8) patients. Also, resistance exercise improved pain, general fatigue, and elbow flexion force in lean women, whereas in overweight and obese FM patients, resistance exercise only improved elbow flexion.
These results indicate that the reduced response to resistance exercise seen in overweight and obese FM patients compared to lean women is associated with differences in the levels of metabolic factors.
“The clearest clinical response to resistance exercise was found in lean patients with FM,” the researchers concluded. “In these individuals, individualized resistance exercise was followed by changes in IGF-1 and leptin, reduced pain, fatigue and improved muscular strength. In overweight and obese women FM markers of metabolic signaling and clinical symptoms were unchanged, but strength was improved in the upper limb. Resistance exercise combined with dietary interventions might benefit patients with FM and overweight.”
Two study limitations that researchers noted were the small number of participants and the relatively short study period. In particular, they proposed that exercise for a longer period may benefit FM patients with obesity.