title: Exercise and hypoxia increase sickling in venous blood from an exercising limb in individuals with sickle cell trait.
abstract: OBJECTIVE
  The association between sickle cell trait (SCT) and complications related to exercise may be explained if exercise-induced sickling interferes with capillary blood flow and causes tissue ischemia and functional abnormalities. To test this hypothesis, we measured sickling and blood gas values in venous and arterial blood of an exercising limb in subjects with SCT and in controls.
  
  
  METHODS
  The study consisted of 15 subjects with hemoglobin AS (SCT group) and 15 subjects with hemoglobin AA (control group). Each performed two maximal arm crank exercise tests, one at 1,270 meters and one at simulated 4,000 meters.
  
  
  RESULTS
  At 1,270 meters, axillary venous sickling increased significantly (p less than 0.05) from (mean +/- SD) 1.0 +/- 1.0% at rest to 2.3 +/- 2.6% during peak exercise. At simulated 4,000 meters, sickling increased significantly (p less than 0.001) from 1.5 +/- 1.2% to 8.5 +/- 7.1%. A wide range of sickling during peak exercise was observed (1% to 25%). One minute after exercise at simulated 4,000 meters, venous sickling remained elevated (7.2 +/- 7.8%) despite high levels of oxygen saturation. Arterial sickling (less than 1%) was present in only two subjects. There was no significant difference in oxygen consumption (29.4 +/- 3 versus 30.7 +/- 4 mL/kg/minute) between the subjects with SCT and the controls, nor was there a correlation between exercise performance and sickling (r less than 0.2).
  
  
  CONCLUSIONS
  We conclude that exercise at 1,270 meters slightly, albeit significantly, increased sickling in blood from an exercising limb and that simulated 4,000 meters dramatically potentiated this effect. Sickling in the effluent blood of an exercising limb does not appear to measurably affect overall maximal arm crank exercise performance.
authors.affiliation: Department of Clinical Investigation, William Beaumont Army Medical Center, El Paso, Texas 79920-5001.
authors.forename: T W
authors.initials: TW
authors.lastname: Martin
authors.forename: I M
authors.initials: IM
authors.lastname: Weisman
authors.forename: R J
authors.initials: RJ
authors.lastname: Zeballos
authors.forename: S R
authors.initials: SR
authors.lastname: Stephenson
mesh_terms: D000328:Adult; D000755:Anemia, Sickle Cell / Q000097:blood*; D001772:Blood Cell Count; D001784:Blood Gas Analysis; D004912:Erythrocytes / Q000473:pathology*; D005221:Fatigue / Q000503:physiopathology; D006451:Hemoglobin, Sickle / Q000032:analysis; D006801:Humans; D000860:Hypoxia / Q000097:blood*; D008297:Male; D010101:Oxygen Consumption; D005082:Physical Exertion; D012805:Sickle Cell Trait / Q000097:blood* / Q000503:physiopathology; D014680:Veins
chemical_list: D006451:Hemoglobin, Sickle