The impact of a cold pressor test on brachial artery handgrip exercise-induced flow-mediated dilation

It is unknown how endothelial-dependent flow-mediated dilation (FMD) stimulated by a sustained, exercise-induced increase in shear stress (EX-FMD) is affected by a simultaneous sympathoexcitatory painful stimulus. The purpose of this study was to examine the impact of a cold pressor test (CPT) on brachial artery EX-FMD elicited by a handgrip exercise-induced increase in shear stress. Participants were healthy males (age 21 +/- 2 years) (n=28; 16 Experimental group, 12 Control). Brachial artery diameter and blood velocity were measured using echo and Doppler ultrasound, respectively. Shear stress was estimated by shear rate (shear rate = blood velocity / diameter) and targeted to reach 75 s(-1) in each of two EX-FMD trials in all subjects. In the Experimental group, the second EX-FMD trial was accompanied by simultaneous foot immersion in ice water (simultaneous CPT). The shear rate stimulus did not differ between groups (p=0.823) or trials (p=0.726) (group x trial interaction: p=0.646) (average exercise shear rate (mean +/- SD): 67.6 +/- 6.2 s(-1)). The CPT (experienced during EX-FMD trial 2 in the Experimental group) increased mean arterial pressure (p<0.001) and heart rate (p=0.002) relative to the Control group. %EX-FMD was not different between groups (p=0.508) or trials (p=0.592) (group x trial interaction: p=0.879) (EX-FMD: Experimental group trial 1: 5.4 +/- 3.4%, trial 2: 5.6 +/- 2.6%; Control group trial 1: 6.0 +/- 3.7%, trial 2: 6.4 +/- 2.2%). In conclusion, the CPT did not impact concurrent EX-FMD, and this indicates that an acute painful stimulus does not interfere with conduit artery FMD responses during exercise in young healthy men.