title: Lack of age-related increase in carotid artery wall viscosity in cardiorespiratory fit men.
abstract: OBJECTIVE
  Age-related arterial stiffening and reduction of arterial elasticity are attenuated in individuals with high levels of cardiorespiratory fitness. Viscosity is another mechanical characteristic of the arterial wall; however, the effects of age and cardiorespiratory fitness have not been determined. We examined the associations among age, cardiorespiratory fitness and carotid arterial wall viscosity.
  
  
  METHODS
  A total of 111 healthy men, aged 25-39 years (young) and 40-64 years (middle-aged), were divided into either cardiorespiratory fit or unfit groups on the basis of peak oxygen uptake. The common carotid artery was measured noninvasively by tonometry and automatic tracking of B-mode images to obtain instantaneous pressure and diameter hysteresis loops, and we calculated the effective compliance, isobaric compliance and viscosity index.
  
  
  RESULTS
  In the middle-aged men, the viscosity index was larger in the unfit group than in the fit group (2533 vs. 2018 mmHg·s/mm, respectively: P<0.05), but this was not the case in the young men. In addition, effective and isobaric compliance were increased, and viscosity index was increased with advancing age, but these parameters were unaffected by cardiorespiratory fitness level.
  
  
  CONCLUSIONS
  These results suggest that the wall viscosity in the central artery is increased with advancing age and that the age-associated increase in wall viscosity may be attenuated in cardiorespiratory fit men.
authors.affiliation: aFaculty of Sport Sciences, Waseda University, Saitama bDepartment of Health Promotion and Exercise, National Institute of Health and Nutrition, Tokyo cFaculty of Letters, Kokushikan University, Tokyo, Japan dDepartment of Integrative Physiology, University of North Texas Health Science Centre, Fort Worth, Texas, USA eFaculty of Biology-Oriented Science and Technology, Kinki University, Wakayama fDepartment of Social Psychiatry, National Institute of Mental Health, National Center of Neurology and Psychiatry, Tokyo gFaculty of Sport and Health Science, Ritsumeikan University, Shiga, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Kawano
authors.forename: Kenta
authors.initials: K
authors.lastname: Yamamoto
authors.forename: Yuko
authors.initials: Y
authors.lastname: Gando
authors.forename: Michiya
authors.initials: M
authors.lastname: Tanimoto
authors.forename: Haruka
authors.initials: H
authors.lastname: Murakami
authors.forename: Yumi
authors.initials: Y
authors.lastname: Ohmori
authors.forename: Kiyoshi
authors.initials: K
authors.lastname: Sanada
authors.forename: Izumi
authors.initials: I
authors.lastname: Tabata
authors.forename: Mitsuru
authors.initials: M
authors.lastname: Higuchi
authors.forename: Motohiko
authors.initials: M
authors.lastname: Miyachi
mesh_terms: D000328:Adult; D000375:Aging / Q000502:physiology*; D002320:Cardiovascular Physiological Phenomena; D002339:Carotid Arteries / Q000502:physiology*; D003187:Compliance; D006801:Humans; D008297:Male; D008875:Middle Aged; D010809:Physical Fitness; D012143:Respiratory Physiological Phenomena; D014783:Viscosity
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