Prehypertension and stress reactivity Medeiros RF et al. Dynamic exercise involving large muscle groups requires complex integrative cardiovascular responses,9 and some effects of exercise on the cardiovascular system can still be observed hours after the exercise ceases.10-12 It has been shown that an acute bout of dynamic exercise decreases blood pressure reactivity to psychosocial stressors in subjects with borderline HT.8,13 However, the mechanism that mediates this response is not known. Specifically, it is not known whether the blunted muscle vasodilation during mental stress in subjects with PHT is improved after a bout of dynamic exercise. Thus, the purpose of this study was to evaluate blood pressure and vascular responses to mental stress experienced before and after a bout of dynamic exercise in subjects with PHT. MATERIALS AND METHODS Sample Subjects were recruited through advertisements in the university and in local newspapers. The sample was composed of 34 subjects, of whom 18 had PHT and 16 had normotension (NT). Eligibility for the study was verified through a clinical history assessment (performed using a questionnaire consisting of questions on cardiovas- cular history and risk factors for cardiovascular disease),14 a physical examination, two blood pressure measurements per day performed on two different days, biochemical blood analyses, a resting electrocardiogram, and maximal cardio- pulmonary exercise testing. All of the subjects fulfilled the following criteria: age between 18 and 49 years, women had regular menstrual cycles, no chronic diseases, no recent 2 infections, body mass index between 18.5 and 29.9 kg/m , glycemia lower than 5.6 mmol/l,15 total cholesterol lower than 6.21 mmol/l,16 low-density lipoprotein lower than 4.14 mmol/l,16 triglycerides lower than 2.26 mmol/l,16 non-smoker, not using medications other than oral contra- ceptives, normal resting and exercise electrocardiogram, and sedentary (not engaged in exercise activities lasting 30 minutes or more, three times per week during the last three months). The study procedures were approved by the Ethics Committee of the Antonio Pedro University Hospital, and written informed consent was obtained from all participants prior to the experimental procedures. Blood pressure assessment Blood pressure was measured in the right arm in the supine position after ten minutes of quiet rest. Measurements were performed with a calibrated mercury sphygmoman- ometer and a cuff size that was appropriate for the arm circumference of each subject. According to The Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure,1 NT was defined as systolic blood pressure (SBP) ,120 mm Hg and diastolic blood pressure (DBP) ,80 mm Hg, and PHT was defined as SBP between 120 and 139 and/ or DBP between 80 and 89 mmHg. The classification was based on the average of four SBP and DBP measurements, where two measurements were taken during each of two visits to the laboratory. The mean blood pressure (MBP) was calculated with the equation [SBP + (2?DBP)]/3. Biochemical blood analyses Plasma glucose was measured with an enzymatic in-vitro test, and serum insulin was determined using an electro- chemiluminescence assay. The homeostasis model assessment 1524 CLINICS 2011;66(9):1523-1529 was calculated to provide an index of insulin resistance.17 Cholesterol and its subfractions, triglycerides and C-reactive protein were determined by the dry chemistry method. Anthropometric analysis Anthropometric assessments included measurements of body weight (adult mechanical balance 110 CH, Welmy, Santa Barbora d’ Oeste, SP, Brazil) and height followed by a calculation of the body mass index. The waist circumference was obtained with a tape measure at the point midway between the last costal margin and the iliac crest with the subject standing and breathing normally.18 Experimental protocol After the initial clinical and laboratory screening, there was an experimental visit that occurred in the morning, one hour after a standardized light breakfast with low-fat foods selected by a dietitian. Women were evaluated from the first until the 12th day after the onset of menstruation. Subjects did not drink alcohol or caffeinated beverages and did not perform intense physical activity for at least 24 hours before the experimental visit. For the experiment, the subjects were placed in supine position in a quiet air conditioned room (¡24˚C). After instrumentation, they rested quietly for ten minutes. The experimental protocol consisted of blood pressure and forearm vascular reactivity assessments at baseline and during mental stress, and these measurements were performed before and 60 minutes after a maximal cardiopulmonary exercise test. Hemodynamic measurements Forearm blood flow (FBF) was measured by venous occlusion plethysmography. The subjects were placed in the supine position with the right arm supported comfortably above the level of the heart. Two cuffs were used: one (8-cm width) was placed around the right wrist, and the other (10- cm width) was placed around the right upper arm. The last cuff was attached to a rapid cuff inflator (EC6; Hokanson, Bellevue, Washington, USA). A mercury-in-silastic strain gauge was placed at the widest girth of the right forearm. The diameter of the strain gauge was 2 cm less than the widest girth of the forearm. The FBF was calculated using a semi-automatic method that has high intra- and inter- evaluator reproducibility (intraclass correlation coefficients between 0.98 and 0.99).19 To measure the BF, the wrist cuff was inflated to 220 mmHg one minute before the onset of the FBF measurement to isolate the vascular circulation of the hand, and it was kept inflated throughout the blood flow measurement.20 At the beginning of all measurements, the evaluator generated a standard calibration pulse of 1 millivolt. The FBF was measured by rapidly inflating the cuff placed around the right upper arm to 50 mmHg (in less than 0.5 s), maintaining this pressure for 10 s and then rapidly deflating it to 0 mmHg for 10 s, thus completing a 20-s cycle. Six cycles of 20 s were performed to determine the baseline FBF, totaling 120 s of baseline measurement. The blood pressure was obtained once during the two minutes of baseline FBF recording. The measurement of FBF during the mental stress test was similar to that during the baseline measurement, but it was performed in nine 20-s cycles (10-s inflation to 50 mmHg followed by 10-s deflation to 0 mmHg), totaling