title: Submaximal exercise testing with near-infrared spectroscopy in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome patients compared to healthy controls: a case-control study.
abstract: BACKGROUND
  Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) is a debilitating illness. Symptoms include profound fatigue and distinctive post-exertional malaise (PEM). We asked whether a submaximal exercise test would prove useful for identifying different patterns of tissue oxygen utilization in individuals with ME/CFS versus healthy subjects. Such a test has potential to aid with ME/CFS diagnosis, or to characterize patients' illness.
  
  
  METHODS
  A case-control study of 16 patients with ME/CFS compared to 16 healthy controls completing a 3-min handgrip protocol was performed. Response was measured using near-infrared spectroscopy, resulting in measurements of oxygenated (O2Hb) and deoxygenated hemoglobin (HHb) over wrist extensors and flexors. Changes in O2Hb (delta (d)O2Hb) and HHb (dHHb) absorbance between the first and last contraction were calculated, as were the force-time product of all contractions, measured as tension-time index (TTI), and ratings of perceived exertion (RPE).
  
  
  RESULTS
  Individuals with ME/CFS demonstrated smaller dO2Hb and dHHb than controls. However, after adjusting for TTI and change in total hemoglobin (delta (d)tHb), differences in dO2Hb and dHHb were reduced, with large overlapping variances. RPE was significantly higher for cases than controls, particularly at rest.
  
  
  CONCLUSIONS
  Relative to controls, participants with ME/CFS demonstrated higher RPE, lower TTI, and reduced dO2Hb and dHHb during repetitive handgrip exercise, although considerable variance was observed. With further study, submaximal exercise testing may prove useful for stratifying patients with a lower propensity for inducing PEM, and have the ability to establish baseline intensities for exercise prescription.
authors.affiliation: School of Population and Public Health, British Columbia Centre for Disease Control, University of British Columbia, 655 West 12th Avenue, Vancouver, BC, V5Z 4R4, Canada. ruth.miller@bccdc.ca.
authors.forename: Ruth R
authors.initials: RR
authors.lastname: Miller
authors.affiliation: Department of Physical Therapy, University of Toronto, 160-500 University Avenue, Toronto, ON, M5G 1V7, Canada. darlene.reid@utoronto.ca.
authors.forename: W Darlene
authors.initials: WD
authors.lastname: Reid
authors.affiliation: Adult Metabolic Disease Clinic, Vancouver General Hospital, Level 4, 2775 Laurel Street, Vancouver, BC, V5Z 1M9, Canada. amattman@providencehealth.bc.ca.
authors.forename: Andre
authors.initials: A
authors.lastname: Mattman
authors.affiliation: Muscle Biophysics Laboratory, Department of Physical Therapy, University of British Columbia, 828 West 10th Avenue, Vancouver, BC, V5Z 3P1, Canada. cristiyama@gmail.com.
authors.forename: Cristiane
authors.initials: C
authors.lastname: Yamabayashi
authors.affiliation: Department of Medicine, Vancouver General Hospital, University of British Columbia, Vancouver, BC, V5Z 3J5, Canada. flagellin@gmail.com.
authors.forename: Theodore
authors.initials: T
authors.lastname: Steiner
authors.affiliation: Centre for Health Evaluation and Outcome Sciences, 588-1081 Burrard Street, Vancouver, BC, V6Z 1Y6, Canada. sparker@cheos.ubc.ca.
authors.forename: Shoshana
authors.initials: S
authors.lastname: Parker
authors.affiliation: British Columbia Centre for Disease Control, 655 West 12th Avenue, Vancouver, BC, V5Z 4R4, Canada. jennifer.gardy@bccdc.ca.
authors.forename: Jennifer
authors.initials: J
authors.lastname: Gardy
authors.affiliation: British Columbia Centre for Disease Control, 655 West 12th Avenue, Vancouver, BC, V5Z 4R4, Canada. Patrick.tang@bccdc.ca.
authors.forename: Patrick
authors.initials: P
authors.lastname: Tang
authors.affiliation: School of Population and Public Health, British Columbia Centre for Disease Control, University of British Columbia, 655 West 12th Avenue, Vancouver, BC, V5Z 4R4, Canada. david.patrick@ubc.ca.|British Columbia Centre for Disease Control, 655 West 12th Avenue, Vancouver, BC, V5Z 4R4, Canada. david.patrick@ubc.ca.
authors.forename: David M
authors.initials: DM
authors.lastname: Patrick
mesh_terms: D000368:Aged; D016022:Case-Control Studies; D015331:Cohort Studies; D004679:Encephalomyelitis / Q000150:complications / Q000628:therapy*; D005080:Exercise Test; D005221:Fatigue; D015673:Fatigue Syndrome, Chronic / Q000150:complications / Q000628:therapy*; D005260:Female; D018737:Hand Strength; D006454:Hemoglobins / Q000737:chemistry; D006801:Humans; D008875:Middle Aged; D010100:Oxygen / Q000737:chemistry; D019265:Spectroscopy, Near-Infrared
chemical_list: D006454:Hemoglobins; D010100:Oxygen