title: Erythrocyte sickling during exercise and thermal stress.
abstract: OBJECTIVE
  To examine effects of exercise in the heat and fluid intake on erythrocyte sickling and neutrophil activation in carriers of sickle cell trait (HbAS).
  
  
  METHODS
  Six African American men (2 HbAS; 42% HbS, 4 HbAA; 20.7 +/- 0.8 years; 87.4 +/- 9.6 kg) participated in 2 randomized sessions (separate days) each consisting of 45 minutes of brisk walking (treadmill) in a hot (33 degrees C) environment.
  
  
  METHODS
  Subjects consumed no fluids or fluid for 3 hours prior to (ad libitum) and during (1.02 L) testing.
  
  
  METHODS
  Core temperature, heart rate, and perceived exertion were measured. Forearm venous blood was analyzed for percent erythrocyte sickling and plasma myeloperoxidase.
  
  
  RESULTS
  Time-averaged heart rate (126.6 +/- 5.7 vs. 146.7 +/- 5.9 bpm; P = 0.02) and core temperature (37.6 +/- 0.1 vs. 38.1 +/- 0.1 degrees C; P < 0.05) responses were lower during fluid versus no fluid, with no statistically significant difference in perceived exertion (12.3 +/- 0.5 vs. 13.6 +/- 0.4; P = 0.06). Erythrocyte sickling progressively increased (to 3.5%-5.5%) for HbAS carriers during no fluid exercise only. No sickling was detected in HbAA subjects. Plasma myeloperoxidase responses to exercise were greater (P = 0.03) in HbAS versus HbAA.
  
  
  CONCLUSIONS
  Fluid ingestion at a rate sufficient to offset a body weight deficit can effectively reduce erythrocyte sickling during exercise in the heat.
authors.affiliation: Department of Physical Therapy, Medical College of Georgia, Augusta, GA 30912-0800, USA. mbergero@mcg.edu
authors.forename: Michael F
authors.initials: MF
authors.lastname: Bergeron
authors.forename: Joseph G
authors.initials: JG
authors.lastname: Cannon
authors.forename: Elaina L
authors.initials: EL
authors.lastname: Hall
authors.forename: Abdullah
authors.initials: A
authors.lastname: Kutlar
mesh_terms: D000328:Adult; D001741:Black or African American / Q000235:genetics*; D001833:Body Temperature Regulation; D016022:Case-Control Studies; D004913:Erythrocytes, Abnormal / Q000378:metabolism*; D015444:Exercise / Q000502:physiology*; D006339:Heart Rate; D006579:Heterozygote; D006358:Hot Temperature; D006801:Humans; D008297:Male; D010101:Oxygen Consumption / Q000502:physiology; D010807:Physical Endurance; D005082:Physical Exertion / Q000502:physiology; D012016:Reference Values; D018570:Risk Assessment; D012680:Sensitivity and Specificity; D012805:Sickle Cell Trait / Q000235:genetics*; D013312:Stress, Physiological