title: Suppression of the reactive hyperemic response in the forearm due to local hand cooling.
abstract: METHODS
  Forearm blood flow (FBF) was measured by electrical impedance plethysmography in order to identify the influence of local cooling of the contralateral hand after 3 min of arterial occlusion. Ten volunteers (six females, four males) were randomly assigned to the following three experimental conditions on separate days: a) 6 min of local hand cooling (5-7 degrees C); b) 3 min of arterial occlusion of the forearm; and c) combined arterial occlusion and local cooling.
  
  
  RESULTS
  All subjects experienced the typical pressor response during 6 min of hand cooling as evidenced by the significant increase (p < and = 0.05) in heart rate (HR), systolic blood pressure (SBP), and diastolic blood pressure (DBP). The FBF responses demonstrated an immediate increase (p < and = 0.05) within the first 30 s of hand submersion and then progressively declined over the next 5 min. The forearm vascular resistance (FVR = MAP/FBF) made an initial drop during the first 30 s of cooling and then gradually rose to reach peak levels between 5-6 min of cooling. With respect to the hyperemic response, FBF significantly increased (p < and = 0.05) from baseline (mean +/- SEM; 1.09 +/- 0.18 ml x 100 ml-1.min-1) and achieved peak levels (6.75 +/- 0.64 ml x 100 ml-1.min-1) within the initial 30 s of the post-occlusion period. Thereafter, FBF declined rapidly by 30-60 s (1.67 +/- 0.29 ml x 100 ml-1.min-1) and 60-90 s (1.26 +/- 0.33 ml x 100 ml-1.min-1) of the post-occlusion period.
  
  
  CONCLUSIONS
  When the reactive hyperemic response was coupled with hand cooling, FBF increased above baseline values and reached peak levels during the initial 30 s of the post-occlusion period. However, the magnitude of the hyperemic response was significantly lower in the cold condition compared to the hyperemia alone (3.20 +/- 0.42 vs 6.75 +/- 0.64 ml x 100 ml-1.min-1; p < and = 0.05). Clearly, the overall sympathetic response to local cooling had an overriding effect on the factors that promote peripheral vasodilation following brief periods (3 min) of arterial occlusion.
authors.affiliation: Department of Exercise Science, Concordia University, Montreal, Quebec, Canada.
authors.forename: R D
authors.initials: RD
authors.lastname: Kilgour
authors.forename: A
authors.initials: A
authors.lastname: Carranza
authors.forename: R
authors.initials: R
authors.lastname: Findlay
mesh_terms: D000328:Adult; D001794:Blood Pressure; D003251:Constriction, Pathologic; D017679:Cryotherapy / Q000379:methods*; D004108:Dilatation, Pathologic; D005260:Female; D005542:Forearm / Q000098:blood supply*; D006339:Heart Rate; D006801:Humans; D006940:Hyperemia / Q000503:physiopathology* / Q000517:prevention & control*; D008297:Male; D010992:Plethysmography, Impedance; D013997:Time Factors; D014655:Vascular Resistance