CLINICS 2011;66(9):1523-1529 180 s of recording of the mental stress FBF. The mean value of each minute of recording was obtained for three cycles, totaling three FBF measurements. Blood pressure was measured three times (once per minute) during the mental stress test using the auscultatory method. The FBF was divided by the mean blood pressure to calculate the forearm vascular conductance (FVC). In addition, the heart rate (HR) was recorded continuously during the mental stress test (Polar Vantage NV, Electro Oy, Kempele, Finland). Mental stress test One of the evaluators explained the traditional color- word conflict task (Stroop Color test) to the subjects.21 A continuous auditory conflict with different names of colors was used to increase the difficulty of the mental stress. Each subject was asked to assess the difficulty of the task according to previously established levels of difficulty: 0 = not stressful; 1 = slightly stressful; 2 = stressful; 3 = very stressful; and 4 = extremely stressful.22 Exercise bout The exercise bout consisted of a standard cardiopulmonary exercise test performed on a treadmill (Master Super ATL, Inbramed, Porto Alegre, RS, Brazil). The protocol was established based on the predicted maximum aerobic capacity (maximal oxygen uptake predicted, based on age, weight, and sex) of each individual.23 The test consisted of a warm-up for three minutes at 3 km/h and 0% grade, followed by a ramp protocol with a linear increase in speed and grade every minute and recovery for five minutes at 4 km/h and 0% grade. The ramp protocol was individua- lized according to the predicted maximal exercise capacity to reach volitional fatigue at approximately ten minutes. The subjects were verbally encouraged to exercise until exhaus- tion. All subjects met at least two of the following criteria to confirm that maximal effort was attained: 1) respiratory exchange ratio .1.1; 2) HR within ¡10 beats/minute of the age-predicted maximum [210 – (age?0.65)]; 3) a perceived effort score of 10 on the Borg 0-10 scale.24 Ventilation, oxygen uptake, and carbon dioxide output were measured with each breath (CPX Ultima Gas Exchange System; Medgraphics, St Paul, Minnesota, USA). Breath-by-breath ventilation and expired gases were averaged over 20 s to identify the peak oxygen consumption (VO2peak), which was considered to be the highest oxygen uptake value during the exercise bout. Statistical analysis The Shapiro–Wilk’s test was used to verify the variables’ distribution. Group characteristics were compared using Student’s t-test, the Mann–Whitney’s test or the Chi-square test when appropriate. FBF and FVC data were log- transformed to normalize their distribution. A two-way analysis of variance (ANOVA) adjusted for gender followed by the Newman-Keuls’ post hoc test was used to compare hemodynamic data before and after exercise between the NT and PHT groups. Statistical significance was established at p,0.05 in two-tailed comparisons. All analyses were performed using the software STATISTICA (version 8; StatSoft Inc., Tulsa, Oklahoma, USA). RESULTS As shown in Table 1, the resting SBP, DBP, and MBP were higher in subjects with PHT than in subjects with NT, as Table 1 - Anthropometric, biochemical, and hemodynamic characteristics of subjects with prehypertension or normotension. Variable N (male%) Age (years) Weight (Kg) BMI (Kg/m2) Waist circumference (cm) Fasting glucose (mmol/l) Fasting insulin (pmol/l) HOMA-IR* Cholesterol (mmol/l) HDL (mmol/l) LDL (mmol/l) Triglyceride (mmol/l) CRP (mg/L)* SBP (mm Hg) DBP (mm Hg) MBP (mm Hg) VO2peak (ml/kg min) 18 (33.3%) 34¡2 69.5¡2.7 25.4¡0.5 80¡2 4.8¡0.1 41.3¡6.8 0.9¡1.9 4.6¡0.2 1.5¡0.1 2.6¡0.2 1.1¡0.1 0.4¡0.4 126¡2 78¡2 95¡2 32¡2 16 (12.5%) 33¡3 68.8¡2.4 24.9¡0.6 81¡2 4.6¡0.1 42.8¡6.7 1.2¡0.8 4.7¡0.2 1.5¡0.1 2.8¡0.1 0.8¡0.1 0.5¡0.5 111¡2 70¡2 84¡2 31¡2 0.15 0.80 0.44 0.93 0.27 0.55 0.73 0.65 0.66 0.20 0.28 0.73 0.65 ,0.01 0.02 ,0.01 0.67 Prehypertension and stress reactivity Medeiros RF et al. Prehypertension Normotension p-value 1525 Data are the mean ¡ SEM or (*) median ¡ interquartile range. BMI indicates body mass index; HOMA, homeostasis model assessment; HDL, high-density lipoprotein; LDL, low-density lipoprotein; CRP, C-reactive protein; SBP, systolic blood pressure; DPB, diastolic blood pressure; MBP, mean blood pressure; VO2peak, peak oxygen uptake. would be expected. However, there were no differences between the groups regarding anthropometric, biochemical, or exercise capacity variables. Figure 1 shows the absolute values of the hemodynamic variables at baseline and during mental stress, which were obtained before and after a single bout of maximal dynamic exercise. Before the exercise bout, the group with PHT had higher FBF and FVC values at baseline than the group with NT. SBP, DBP, MBP, and HR increased during mental stress in both groups, whereas FBF and FVC increased only in the group with NT. In addition, the group with PHT had higher SBP, DBP, and MBP during mental stress compared with the group with NT. After the exercise bout, baseline SBP, FBF, and FVC decreased only in the group with PHT; DBP and MBP increased only in the group with NT; and HR increased in both groups com- pared with the values obtained before the exercise bout. Furthermore, all variables increased during mental stress in both groups. However, in the PHT group, SBP, DBP, and MBP were lower and HR was higher during the mental stress after the exercise bout than before. In the NT group, SBP was higher but HR, FBF, and FVC were lower during the mental stress after the exercise bout than before. Finally, the SBP during mental stress was higher in the group with PHT than in the group with NT. There was no difference in mental stress scores before and after exercise within the groups (PHT: before exercise 2¡0 vs. after exercise 2¡2, p = 0.58; NT: before exercise 2¡2 vs. after exercise 2¡2, p = 0.81). Figure 2 shows the percent change of hemodynamic variables in response to mental stress before and after a single bout of maximal dynamic exercise. Before the exercise bout, FBF and FVC percent change values were lower in the PHT group than in the NT group. After the exercise bout, FBF and FVC percent change values in the PHT group increased relative to the values obtained before the exercise bout, and thus, there was no longer any difference between the groups. It is worth noting that there was 80% power in the FVC percent change analysis, which was the main