title: Exercise efficiency relates with mitochondrial content and function in older adults.
abstract: Chronic aerobic exercise has been shown to increase exercise efficiency, thus allowing less energy expenditure for a similar amount of work. The extent to which skeletal muscle mitochondria play a role in this is not fully understood, particularly in an elderly population. The purpose of this study was to determine the relationship of exercise efficiency with mitochondrial content and function. We hypothesized that the greater the mitochondrial content and/or function, the greater would be the efficiencies. Thirty-eight sedentary (S, n = 23, 10F/13M) or athletic (A, n = 15, 6F/9M) older adults (66.8 ± 0.8 years) participated in this cross sectional study. V˙O2peak was measured with a cycle ergometer graded exercise protocol (GXT). Gross efficiency (GE, %) and net efficiency (NE, %) were estimated during a 1-h submaximal test (55% V˙O2peak). Delta efficiency (DE, %) was calculated from the GXT. Mitochondrial function was measured as ATPmax (mmol/L/s) during a PCr recovery protocol with (31)P-MR spectroscopy. Muscle biopsies were acquired for determination of mitochondrial volume density (MitoVd, %). Efficiencies were 17% (GE), 14% (NE), and 16% (DE) higher in A than S. MitoVD was 29% higher in A and ATPmax was 24% higher in A than in S. All efficiencies positively correlated with both ATPmax and MitoVd. Chronically trained older individuals had greater mitochondrial content and function, as well as greater exercise efficiencies. GE, NE, and DE were related to both mitochondrial content and function. This suggests a possible role of mitochondria in improving exercise efficiency in elderly athletic populations and allowing conservation of energy at moderate workloads.
authors.affiliation: Department of Physiology, School of Biology and Medicine, University of Lausanne, Lausanne, Switzerland.
authors.forename: Nicholas T
authors.initials: NT
authors.lastname: Broskey
authors.affiliation: Department of Clinical Research & Institute of Interventional, Diagnostic and Pediatric Radiology, University of Bern, Bern, Switzerland.
authors.forename: Andreas
authors.initials: A
authors.lastname: Boss
authors.affiliation: Department of Physiology, School of Biology and Medicine, University of Lausanne, Lausanne, Switzerland.
authors.forename: Elie-Jacques
authors.initials: EJ
authors.lastname: Fares
authors.affiliation: Department of Physiology, School of Biology and Medicine, University of Lausanne, Lausanne, Switzerland.
authors.forename: Chiara
authors.initials: C
authors.lastname: Greggio
authors.affiliation: Sports Medicine Unit, University Hospital, Lausanne, Switzerland.
authors.forename: Gerald
authors.initials: G
authors.lastname: Gremion
authors.affiliation: Service of Cardiology, University Hospital, Lausanne, Switzerland.
authors.forename: Leo
authors.initials: L
authors.lastname: Schlüter
authors.affiliation: Center for Bone Disease, Bone & Joint Department, University Hospital, Lausanne, Switzerland.
authors.forename: Didier
authors.initials: D
authors.lastname: Hans
authors.affiliation: Department of Clinical Research & Institute of Interventional, Diagnostic and Pediatric Radiology, University of Bern, Bern, Switzerland.
authors.forename: Roland
authors.initials: R
authors.lastname: Kreis
authors.affiliation: Department of Clinical Research & Institute of Interventional, Diagnostic and Pediatric Radiology, University of Bern, Bern, Switzerland.
authors.forename: Chris
authors.initials: C
authors.lastname: Boesch
authors.affiliation: Department of Physiology, School of Biology and Medicine, University of Lausanne, Lausanne, Switzerland Sports Medicine Unit, University Hospital, Lausanne, Switzerland Francesca.amati@unil.ch.
authors.forename: Francesca
authors.initials: F
authors.lastname: Amati
keywords: Chronic exercise; delta efficiency; gross efficiency; net efficiency