title: Mitochondrial capacity, muscle endurance, and low energy in friedreich ataxia.
abstract: BACKGROUND
  In this study we noninvasively evaluated skeletal muscle mitochondrial capacity, muscle-specific endurance, and energy/fatigue feelings in persons with Friedreich ataxia (FRDA) and able-bodied controls (AB).
  
  
  METHODS
  Forearm mitochondrial capacity was measured in FRDA (n = 16) and AB (n = 10) study participants using the rate of recovery of oxygen consumption after electrical stimulation with near-infrared spectroscopy. Mechanomyography (MMG) assessed muscle endurance after electrical stimulation for 3 minutes at 2 Hz, 4 Hz, and 6 Hz. Validated scales assessed disease severity and energy/fatigue feelings.
  
  
  RESULTS
  Groups did not differ in mitochondrial capacity (FRDA and AB: 1.8 ± 0.3 L/min). The difference in muscle endurance at 6 Hz was lower by 19.2% in the FRDA group (group effect: P < 0.001). Feelings of physical energy were 34% lower in FRDA group. In FDRA muscle, endurance was positively related to mitochondrial capacity (r = 0.59, P = 0.03), and disease severity was negatively related to mitochondrial capacity (r = -0.55, P = 0.04) and muscle endurance (r = -0.60, P = 0.01).
  
  
  CONCLUSIONS
  Non-invasive measures of skeletal muscle mitochondrial capacity and muscle-specific endurance are useful in monitoring FRDA. Muscle Nerve 56: 773-779, 2017.
authors.affiliation: Department of Kinesiology, University of Georgia, 330 River Road, Athens, Georgia, 30605, USA.
authors.forename: Hannah M
authors.initials: HM
authors.lastname: Bossie
authors.affiliation: Department of Kinesiology, University of Georgia, 330 River Road, Athens, Georgia, 30605, USA.
authors.forename: T Bradley
authors.initials: TB
authors.lastname: Willingham
authors.affiliation: Department of Kinesiology, University of Georgia, 330 River Road, Athens, Georgia, 30605, USA.
authors.forename: Robbi A Van
authors.initials: RAV
authors.lastname: Schoick
authors.affiliation: Department of Kinesiology, University of Georgia, 330 River Road, Athens, Georgia, 30605, USA.
authors.forename: Patrick J
authors.initials: PJ
authors.lastname: O'Connor
authors.affiliation: Department of Kinesiology, University of Georgia, 330 River Road, Athens, Georgia, 30605, USA.
authors.forename: Kevin K
authors.initials: KK
authors.lastname: McCully
mesh_terms: D000293:Adolescent; D000328:Adult; D002648:Child; D003430:Cross-Sectional Studies; D004734:Energy Metabolism / Q000502:physiology*; D005260:Female; D005621:Friedreich Ataxia / Q000378:metabolism* / Q000503:physiopathology; D006801:Humans; D008297:Male; D008875:Middle Aged; D008931:Mitochondria, Muscle / Q000378:metabolism*; D018763:Muscle Fatigue / Q000502:physiology*; D018482:Muscle, Skeletal / Q000378:metabolism* / Q000503:physiopathology; D010101:Oxygen Consumption / Q000502:physiology; D010807:Physical Endurance / Q000502:physiology*; D055815:Young Adult
keywords: affect; disease severity; fatigability; fatigue; mechanomyography; near-infrared spectroscopy; non-invasive measurements