title: Skeletal Muscle Mitochondrial Function and Fatigability in Older Adults.
abstract: BACKGROUND
  Fatigability increases while the capacity for mitochondrial energy production tends to decrease significantly with age. Thus, diminished mitochondrial function may contribute to higher levels of fatigability in older adults.
  
  
  METHODS
  The relationship between fatigability and skeletal muscle mitochondrial function was examined in 30 participants aged 78.5 ± 5.0 years (47% female, 93% white), with a body mass index of 25.9 ± 2.7 kg/m(2) and usual gait-speed of 1.2 ± 0.2 m/s. Fatigability was defined using rating of perceived exertion (6-20 point Borg scale) after a 5-minute treadmill walk at 0.72 m/s. Phosphocreatine recovery in the quadriceps was measured using (31)P magnetic resonance spectroscopy and images of the quadriceps were captured to calculate quadriceps volume. ATPmax (mM ATP/s) and oxidative capacity of the quadriceps (ATPmax·Quadriceps volume) were calculated. Peak aerobic capacity (VO2peak) was measured using a modified Balke protocol.
  
  
  RESULTS
  ATPmax·Quadriceps volume was associated with VO2peak and was 162.61mM ATP·mL/s lower (p = .03) in those with high (rating of perceived exertion ≥10) versus low (rating of perceived exertion ≤9) fatigability. Participants with high fatigability required a significantly higher proportion of VO2peak to walk at 0.72 m/s compared with those with low fatigability (58.7 ± 19.4% vs 44.9 ± 13.2%, p < .05). After adjustment for age and sex, higher ATPmax was associated with lower odds of having high fatigability (odds ratio: 0.34, 95% CI: 0.11-1.01, p = .05).
  
  
  CONCLUSIONS
  Lower capacity for oxidative phosphorylation in the quadriceps, perhaps by contributing to lower VO2peak, is associated with higher fatigability in older adults.
authors.affiliation: Department of Epidemiology, Center for Aging and Population Health, Graduate School of Public Health, University of Pittsburgh, Pennsylvania.
authors.forename: Adam J
authors.initials: AJ
authors.lastname: Santanasto
authors.affiliation: Department of Epidemiology, Center for Aging and Population Health, Graduate School of Public Health, University of Pittsburgh, Pennsylvania. glynnn@edc.pitt.edu.
authors.forename: Nancy W
authors.initials: NW
authors.lastname: Glynn
authors.affiliation: Translational Center for Metabolic Imaging, University of Washington, Seattle.
authors.forename: Sharon A
authors.initials: SA
authors.lastname: Jubrias
authors.affiliation: Translational Center for Metabolic Imaging, University of Washington, Seattle.
authors.forename: Kevin E
authors.initials: KE
authors.lastname: Conley
authors.affiliation: Department of Epidemiology, Center for Aging and Population Health, Graduate School of Public Health, University of Pittsburgh, Pennsylvania.
authors.forename: Robert M
authors.initials: RM
authors.lastname: Boudreau
authors.affiliation: Division of Endocrinology and Metabolism, School of Medicine, University of Pittsburgh, Pennsylvania.
authors.forename: Francesca
authors.initials: F
authors.lastname: Amati
authors.affiliation: Department of Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, Canada.
authors.forename: Dawn C
authors.initials: DC
authors.lastname: Mackey
authors.affiliation: Translational Gerontology Branch, National Institute on Aging, Baltimore, Maryland.
authors.forename: Eleanor M
authors.initials: EM
authors.lastname: Simonsick
authors.affiliation: Department of Epidemiology, Center for Aging and Population Health, Graduate School of Public Health, University of Pittsburgh, Pennsylvania.
authors.forename: Elsa S
authors.initials: ES
authors.lastname: Strotmeyer
authors.affiliation: Division of Endocrinology and Metabolism, School of Medicine, University of Pittsburgh, Pennsylvania. Department of Health and Physical Activity, School of Education, University of Pittsburgh, Pennsylvania. Present address: Florida Hospital-Sanford|Burnham Translational Research Institute for Metabolism and Diabetes, Orlando.
authors.forename: Paul M
authors.initials: PM
authors.lastname: Coen
authors.affiliation: Division of Endocrinology and Metabolism, School of Medicine, University of Pittsburgh, Pennsylvania. Present address: Florida Hospital-Sanford|Burnham Translational Research Institute for Metabolism and Diabetes, Orlando.
authors.forename: Bret H
authors.initials: BH
authors.lastname: Goodpaster
authors.affiliation: Department of Epidemiology, Center for Aging and Population Health, Graduate School of Public Health, University of Pittsburgh, Pennsylvania.
authors.forename: Anne B
authors.initials: AB
authors.lastname: Newman
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D015331:Cohort Studies; D004734:Energy Metabolism / Q000502:physiology*; D005080:Exercise Test; D017079:Exercise Tolerance / Q000502:physiology; D005221:Fatigue / Q000209:etiology / Q000378:metabolism* / Q000503:physiopathology*; D005260:Female; D006801:Humans; D008297:Male; D008931:Mitochondria, Muscle / Q000502:physiology*; D052097:Quadriceps Muscle / Q000378:metabolism* / Q000503:physiopathology*; D016138:Walking
chemical_list: D000255:Adenosine Triphosphate
keywords: Aerobic capacity; Fatigability; Mitochondrial function; Skeletal muscle.