In new research published in PLoS One, researchers at Johns Hopkins University School of Medicine in Baltimore and the University of Alabama at Birmingham investigated the effects of neuromuscular strain on symptom ratings of patients with chronic fatigue syndrome (CFS).1
CFS symptoms can be triggered by physical and cognitive exertion, and previous findings show that symptoms can also be elicited by applying strain to to the limb and spine muscles.2 Those results are consistent “with the hypothesis that increased mechanical sensitivity may be a contributor to the generation and exacerbation of CFS symptoms,” the authors wrote.
To extend this line of inquiry, the investigators examined responses of 60 patients with CFS and 20 healthy individuals who were randomly assigned to 1 of 2 conditions: a neuromuscular strain group exposed to 15 minutes of a passive supine straight leg raise, or a sham strain group exposed to 15 minutes of a maneuver similar to the true strain maneuver but insufficient to actually cause strain.
Participants first completed a battery of baseline assessments, including the Multidimensional Fatigue Inventory (MFI), the Center for Epidemiologic Studies-Depression Scale (CES-D), and the Beck Anxiety Inventory (BAI), as well as measures of wellness and symptom intensity.
They also underwent a tenderpoint examination and testing for joint hypermobility before being exposed to their assigned condition. Study participants rated symptom intensity at multiple points: at baseline; every 5 minutes throughout the test; 5 minutes following completion; and in a follow-up call 24 hours later.
Compared with the CFS sham group, the CFS strain group had a mean (95% confidence interval, CI) difference in symptom intensity of 0.94 point greater for body pain, and 1.13 point greater for concentration difficulty.
While no change was observed for lightheadedness during the test, the CFS strain group had mean (95% CI) scores of 1.75 point higher than the CFS sham group at the 24-hour follow-up. In addition, the CFS strain group had higher mean (95% CI) differences in composite symptom scores both during the maneuver and 24 hours later: 3.52 and 4.30 at each time point.
Though the exact mechanisms underlying the observed association between neuromuscular strain and CFS symptom exacerbation are unclear, the present findings “support preliminary observations that increased mechanical sensitivity may be a contributor to the provocation of symptoms in this disorder,” wrote the authors. “Our findings have practical implications for the understanding of why exercise and the activities of daily life might be capable of provoking CFS symptoms,” they concluded.
- Rowe PC, Fontaine KR, Lauver M, et al. Neuromuscular strain increases symptom intensity in chronic fatigue syndrome. PLoS One. 2016; 11(7):e0159386.
- Rowe PC, Marden CL, Flaherty MA, et al. Impaired range of motion of limbs and spine in chronic fatigue syndrome. J Pediatrics. 2014; 165: 360–366.