title: Age- and fitness-related differences in limb venous compliance do not affect tolerance to maximal lower body negative pressure in men and women.
abstract: Aging and chronic exercise training influence leg venous compliance. Venous compliance affects responses to an orthostatic stress; its effect on tolerance to maximal lower body negative pressure (LBNP) in the elderly is unknown. The purpose of this study was to determine the influence of age and fitness, a surrogate measure of exercise training, on calf venous compliance and tolerance to maximal LBNP in men and women. Forty participants, 10 young fit (YF; age = 22.6 +/- 0.5 yr, peak oxygen uptake = 57.1 +/- 2.0 ml.kg(-1).min(-1)), 10 young unfit (YU; 23.1 +/- 1.0 yr, 41.1 +/- 2.0 ml.kg(-1).min(-1)), 10 older fit (OF; 73.9 +/- 2.0 yr, 39.0 +/- 2.0 ml.kg(-1).min(-1)), and 10 older unfit (OU; 70.9 +/- 1.6 yr, 27.1 +/- 2.0 ml.kg(-1).min(-1)), underwent graded LBNP to presyncope or 4 min at -100 mmHg. By utilizing venous occlusion plethysmography, calf venous compliance was determined by using the first derivative of the pressure-volume relation during cuff pressure reduction. We found that the more fit groups had greater venous compliance than their unfit peers (P < 0.05) as did the young groups compared with their older peers (P < 0.05) such that OU < YU = OF < YF. LBNP tolerance did not differ between groups. In conclusion, these data suggest that aging reduces, and chronic exercise increases, venous compliance. However, these data do not support a significant influence of venous compliance on LBNP tolerance.
authors.affiliation: Department of Health and Human Performance, Iowa State University, Ames, Iowa 50011, USA.
authors.forename: J P
authors.initials: JP
authors.lastname: Hernandez
authors.forename: W D
authors.initials: WD
authors.lastname: Franke
mesh_terms: D000222:Adaptation, Physiological / Q000502:physiology; D000328:Adult; D000367:Age Factors; D000375:Aging / Q000502:physiology*; D001794:Blood Pressure / Q000502:physiology*; D003187:Compliance; D005260:Female; D006487:Hemostasis / Q000502:physiology; D006801:Humans; D007866:Leg / Q000502:physiology*; D008150:Lower Body Negative Pressure / Q000379:methods*; D008297:Male; D008875:Middle Aged; D010809:Physical Fitness / Q000502:physiology*; D018924:Vascular Capacitance / Q000502:physiology*; D014680:Veins / Q000502:physiology*