title: Hemorheological correlates of fitness and unfitness in athletes: moving beyond the apparent "paradox of hematocrit"?
abstract: Negative correlations between blood viscosity parameters and fitness have been reported, but their physiological meaning remains incompletely understood. Since rheo-active treatments are used in athletes doping, we aimed at clarifying the relationships between hematocrit (Hct), viscosity and performance by comparing aerobic capacity, overtraining questionnaire, and hemorheological parameters.
  
  
  METHODS
  29 sportsmen (24.71+/-1.05 yr; 74.90+/-1.44 kg; 178.5+/-1.05 cm) underwent a standardised exercise test. Physical working capacity (W170), maximal power output (Wmax) and maximal oxygen consumption (VO2max ) were calculated. Viscometric measurements were done with a MT 90 Medicatest viscosimeter. Hct was measured with microcentrifuge. All subjects answered the overtraining questionnaire proposed by the French Society for Sports Medicine.
  
  
  RESULTS
  The best correlate of maximal power output (Wmax) was whole blood viscosity (r=-0.383, p<0.001). The stepwise regression analysis only selected Hct as W170 determinant (r=-0.66, p<0.001). Similarly the best determinant of VO2max, expressed as a percentage of theoretical values, was Hct (r=-0.462, p=0.01). Hct/viscosity ratio (Hct/eta), a proposed index of Hct's positive influence on O2 transfer to tissues, was positively correlated to Wmax expressed as a percentage of theoretical values (r=0.487, p=0.02). The overtraining score was correlated to plasma viscosity (r=0.450, p=0.016).
  
  
  CONCLUSIONS
  The best hemorheogical correlate of fitness is a low hematocrit and the best hemorheological correlate of overtraining is increased plasma viscosity.
authors.affiliation: Laboratoire de Pharmacocinétique clinique, Faculté de Pharmacie, BP 14491, Université Montpellier I, 34093 Montpellier Cédex 5, France.
authors.forename: A
authors.initials: A
authors.lastname: Gaudard
authors.forename: E
authors.initials: E
authors.lastname: Varlet-Marie
authors.forename: F
authors.initials: F
authors.lastname: Bressolle
authors.forename: J
authors.initials: J
authors.lastname: Mercier
authors.forename: J-F
authors.initials: JF
authors.lastname: Brun
mesh_terms: D000328:Adult; D001809:Blood Viscosity; D001823:Body Composition; D012090:Cumulative Trauma Disorders / Q000097:blood / Q000503:physiopathology; D017097:Electric Impedance; D004903:Erythrocyte Aggregation; D015444:Exercise; D005080:Exercise Test; D017079:Exercise Tolerance; D005293:Ferritins / Q000097:blood; D005340:Fibrinogen / Q000032:analysis; D018737:Hand Strength; D006400:Hematocrit; D018056:Hemorheology; D006801:Humans; D008297:Male; D010101:Oxygen Consumption; D010809:Physical Fitness / Q000502:physiology*; D010992:Plethysmography, Impedance; D013177:Sports / Q000502:physiology*; D011795:Surveys and Questionnaires
chemical_list: D005340:Fibrinogen; D005293:Ferritins