title: Age-related differences in skeletal muscle microvascular response to exercise as detected by contrast-enhanced ultrasound (CEUS).
abstract: BACKGROUND
  Aging involves reductions in exercise total limb blood flow and exercise capacity. We hypothesized that this may involve early age-related impairments of skeletal muscle microvascular responsiveness as previously reported for insulin but not for exercise stimuli in humans.
  
  
  METHODS
  Using an isometric exercise model, we studied the effect of age on contrast-enhanced ultrasound (CEUS) parameters, i.e. microvascular blood volume (MBV), flow velocity (MFV) and blood flow (MBF) calculated from replenishment of Sonovue contrast-agent microbubbles after their destruction. CEUS was applied to the vastus lateralis (VLat) and intermedius (VInt) muscle in 15 middle-aged (MA, 43.6±1.5 years) and 11 young (YG, 24.1±0.6 years) healthy males before, during, and after 2 min of isometric knee extension at 15% of peak torque (PT). In addition, total leg blood flow as recorded by femoral artery Doppler-flow. Moreover, fiber-type-specific and overall capillarisation as well as fiber composition were additionally assessed in Vlat biopsies obtained from CEUS site. MA and YG had similar quadriceps muscle MRT-volume or PT and maximal oxygen uptake as well as a normal cardiovascular risk factors and intima-media-thickness.
  
  
  RESULTS
  During isometric exercise MA compared to YG reached significantly lower levels in MFV (0.123±0.016 vs. 0.208±0.036 a.u.) and MBF (0.007±0.001 vs. 0.012±0.002 a.u.). In the VInt the (post-occlusive hyperemia) post-exercise peaks in MBV and MBF were significantly lower in MA vs. YG. Capillary density, capillary fiber contacts and femoral artery Doppler were similar between MA and YG.
  
  
  CONCLUSIONS
  In the absence of significant age-related reductions in capillarisation, total leg blood flow or muscle mass, healthy middle-aged males reveal impaired skeletal muscle microcirculatory responses to isometric exercise. Whether this limits isometric muscle performance remains to be assessed.
authors.affiliation: Department of Medical Cell Biology, Institute of Anatomy and Cell Biology, University of Marburg, Marburg, Germany.
authors.forename: Wulf
authors.initials: W
authors.lastname: Hildebrandt
authors.affiliation: Department of Medical Cell Biology, Institute of Anatomy and Cell Biology, University of Marburg, Marburg, Germany.
authors.forename: Hans
authors.initials: H
authors.lastname: Schwarzbach
authors.affiliation: Department of Medical Cell Biology, Institute of Anatomy and Cell Biology, University of Marburg, Marburg, Germany.
authors.forename: Anita
authors.initials: A
authors.lastname: Pardun
authors.affiliation: Department of Medical Cell Biology, Institute of Anatomy and Cell Biology, University of Marburg, Marburg, Germany.
authors.forename: Lena
authors.initials: L
authors.lastname: Hannemann
authors.affiliation: Department of Medical Cell Biology, Institute of Anatomy and Cell Biology, University of Marburg, Marburg, Germany.
authors.forename: Björn
authors.initials: B
authors.lastname: Bogs
authors.affiliation: Department of Diagnostic and Interventional Radiology, University Hospital of Giessen and Marburg (UKGM) University, Baldingerstraße, Marburg, Germany.
authors.forename: Alexander M
authors.initials: AM
authors.lastname: König
authors.affiliation: Department of Diagnostic and Interventional Radiology, University Hospital of Giessen and Marburg (UKGM) University, Baldingerstraße, Marburg, Germany.
authors.forename: Andreas H
authors.initials: AH
authors.lastname: Mahnken
authors.affiliation: Department of Sleep Medicine, Division of Pneumology, Internal Medicine, University Hospital of Giessen and Marburg (UKGM) Baldingerstraße, Marburg, Germany.
authors.forename: Olaf
authors.initials: O
authors.lastname: Hildebrandt
authors.affiliation: Department of Sleep Medicine, Division of Pneumology, Internal Medicine, University Hospital of Giessen and Marburg (UKGM) Baldingerstraße, Marburg, Germany.
authors.forename: Ulrich
authors.initials: U
authors.lastname: Koehler
authors.affiliation: Department of Medical Cell Biology, Institute of Anatomy and Cell Biology, University of Marburg, Marburg, Germany.
authors.forename: Ralf
authors.initials: R
authors.lastname: Kinscherf
mesh_terms: D000328:Adult; D000367:Age Factors; D015415:Biomarkers; D001706:Biopsy; D003287:Contrast Media; D003430:Cross-Sectional Studies; D015444:Exercise; D006801:Humans; D007089:Image Enhancement; D008279:Magnetic Resonance Imaging; D008297:Male; D008833:Microcirculation; D008875:Middle Aged; D009119:Muscle Contraction; D018482:Muscle, Skeletal / Q000098:blood supply* / Q000000981:diagnostic imaging / Q000502:physiology*; D012039:Regional Blood Flow; D012307:Risk Factors; D014463:Ultrasonography / Q000379:methods; D055815:Young Adult
chemical_list: D015415:Biomarkers; D003287:Contrast Media