Evening but not morning aerobic training improves sympathetic activity and baroreflex sensitivity in elderly patients with treated hypertension.

The blood pressure-lowering effect of aerobic training is preceded by improving cardiovascular autonomic control. We previously demonstrated that aerobic training conducted in the evening (ET) induces a greater decrease in blood pressure than morning training (MT). To study whether the greater blood pressure decrease after ET occurs through better cardiovascular autonomic regulation, this study aimed to compare MT versus ET on muscle sympathetic nerve activity (MSNA) and baroreflex sensitivity (BRS) in treated patients with hypertension. Elderly patients treated for hypertension were randomly allocated into MT (n = 12, 07.00-10.00 h) or ET (n = 11, 17.00-20.00 h) groups. Both groups trained for 10 weeks, 3 times/week, cycling for 45 min at moderate intensity. Beat-to-beat blood pressure (finger photoplethysmography), heart rate (electrocardiography) and MSNA (microneurography) were assessed at the initial and final phases of the study at baseline and during sequential bolus infusions of sodium nitroprusside and phenylephrine (modified-Oxford technique) to evaluate cardiac and sympathetic BRS. Mean blood pressure decreased significantly after ET but not after MT (-9 ± 11 vs. -1 ± 8 mmHg, P = 0.042). MSNA decreased significantly only after ET with no change after MT (-12 ± 5 vs. -3 ± 7 bursts/100 heart beats, P = 0.013). Sympathetic BRS improved after ET but not after MT (-0.8 ± 0.7 vs. 0.0 ± 0.8 bursts/100 heart beats/mmHg, P = 0.052). Cardiac BRS improved similarly in both groups (ET: +1.7 ± 1.8 vs. MT: +1.4 ± 1.9 ms/mmHg, Pphase  ≤ 0.001). In elderly patients treated for hypertension, only ET decreased mean blood pressure and MSNA and improved sympathetic BRS. These findings revealed that the sympathetic nervous system has a key role in ET's superiority to MT in blood pressure-lowering effect. KEY POINTS: Reducing muscle nerve sympathetic activity and increasing sympathetic baroreflex sensitivity plays a key role in promoting the greater blood pressure reduction observed with evening training. These findings indicated that simply changing the timing of exercise training may offer additional benefits beyond antihypertensive medications, such as protection against sympathetic overdrive and loss of baroreflex sensitivity, independent markers of mortality. Our new findings also suggest new avenues of investigation, such as the possibility that evening aerobic training may be beneficial in other clinical conditions with sympathetic overdrive, such as congestive heart failure and hypertrophic cardiomyopathy.

Effects of dynamic, isometric and combined resistance training on blood pressure and its mechanisms in hypertensive men.

Although dynamic resistance training (DRT) and isometric handgrip training (IHT) may decrease blood pressure (BP) in hypertensives, the effects of these types of training have not been directly compared, and a possible additive effect of combining IHT to DRT (combined resistance training-CRT), has not been investigated. Thus, this study compared the effects of DRT, IHT and CRT on BP, systemic hemodynamics, vascular function, and cardiovascular autonomic modulation. Sixty-two middle-aged men with treated hypertension were randomly allocated among four groups: DRT (8 exercises, 50% of 1RM, 3 sets until moderate fatigue), IHT (30% of MVC, 4 sets of 2 min), CRT (DRT + IHT) and control (CON - stretching). In all groups, the interventions were administered 3 times/week for 10 weeks. Pre- and post-interventions, BP, systemic hemodynamics, vascular function and cardiovascular autonomic modulation were assessed. ANOVAs and ANCOVAs adjusted for pre-intervention values were employed for analysis. Systolic BP decreased similarly with DRT and CRT (125 ± 11 vs. 119 ± 12 and 128 ± 12 vs. 119 ± 12 mmHg, respectively; P < 0.05), while peak blood flow during reactive hyperaemia (a marker of microvascular function) increased similarly in these groups (774 ± 377 vs. 1067 ± 461 and 654 ± 321 vs. 954 ± 464 mL/min, respectively, P < 0.05). DRT and CRT did not change systemic hemodynamics, flow-mediated dilation, and cardiovascular autonomic modulation. In addition, none of the variables were changed by IHT. In conclusion, DRT, but not IHT, improved BP and microvascular function in treated hypertensive men. CRT did not have any additional effect in comparison with DRT alone.

Hydration Does Not Change Postexercise Hypotension and Its Mechanisms.

BACKGROUND: Drinking water is recommended before and after exercise to avoid dehydration. However, water ingestion may mitigate or prevent postexercise hypotension. This study investigated the effects of intentional hydration on postaerobic exercise hemodynamics and autonomic modulation. METHODS: A total of 18 young men randomly underwent 4 experimental sessions as follows: (1) control with intentional hydration (1 L of water in the previous night, 500 mL 60 min before the intervention, and 1 mL for each 1 g of body mass lost immediately after the intervention); (2) control without intentional hydration (ad libitum water ingestion before the intervention); (3) exercise (cycle ergometer, 45 min, 50% of VO2peak) with intentional hydration; and (4) exercise without intentional hydration. Hemodynamic and autonomic parameters were measured before and after the interventions and were compared by 3-way analysis of variance. RESULTS: Intentional hydration did not change any postexercise hemodynamic nor autonomic response. Exercise decreased systolic blood pressure and stroke volume (-4.1 [0.8] mm Hg and -4.9 [1.5] mL, P < .05), while increased cardiac sympathovagal balance (0.3 [0.3], P < .05) during the recovery. In addition, it abolished the increase in diastolic blood pressure and the decrease in heart rate observed in the control sessions. CONCLUSION: Intentional hydration does not modify the hypotensive effect promoted by previous aerobic exercise and did not alter its hemodynamic and autonomic mechanisms.

Separate aftereffects of morning and evening exercise on ambulatory blood pressure in prehypertensive men.

BACKGROUND: Clinic postexercise hypotension (PEH) is different after aerobic exercise performed in the morning and in the evening. Thus, ambulatory PEH should also differ after exercises conducted at different times of day. However, because of the circadian pattern of blood pressure (BP), ambulatory PEH should be assessed considering a control condition. Thus, this study was designed to verify the effects of morning and evening exercises on postexercise ambulatory BP averages and circadian parameters by comparing responses obtained at each time of day after an exercise and a control session. METHODS: Thirteen prehypertensive men underwent four sessions (randomized order): two in the morning (9 am) and two in the evening (6:30 pm). At each time of day, a control (C) and an exercise (E: cycle ergometer 45 min, 50% VO2peak) sessions were performed. After the sessions, an ambulatory BP and heart rate (HR) monitoring was started for 24 h. Paired t-test or Wilcoxon Signed Rank Test were used to compare the E and the C sessions at each time of day. RESULTS: In the morning, 24 h, daytime and nighttime HR were higher after the E than the C session. In the evening, nighttime systolic BP (116±11 vs. 120±10 mmHg, P=0.04) and rate pressure product (7981±1294 vs. 8583±1523 mmHg.bpm, P=0.04), as well as MESOR (128±11 vs. 130±10 mmHg, P=0.03) were lower in the E than the C session. CONCLUSIONS: In prehypertensive men, morning exercise increased ambulatory HR, while evening exercise decreased nighttime BP and cardiac work, reducing the MESOR of systolic BP.

Post-Exercise Hypotension and Its Mechanisms Differ after Morning and Evening Exercise: A Randomized Crossover Study.

Post-exercise hypotension (PEH), calculated by the difference between post and pre-exercise values, it is greater after exercise performed in the evening than the morning. However, the hypotensive effect of morning exercise may be masked by the morning circadian increase in blood pressure. This study investigated PEH and its hemodynamic and autonomic mechanisms after sessions of aerobic exercise performed in the morning and evening, controlling for responses observed after control sessions performed at the same times of day. Sixteen pre-hypertensive men underwent four sessions (random order): two conducted in the morning (7:30 am) and two in the evening (5 pm). At each time of day, subjects underwent an exercise (cycling, 45 min, 50%VO2peak) and a control (sitting rest) session. Measurements were taken pre- and post-interventions in all the sessions. The net effects of exercise were calculated for each time of day by [(post-pre exercise)-(post-pre control)] and were compared by paired t-test (P<0.05). Exercise hypotensive net effects (e.g., decreasing systolic, diastolic and mean blood pressure) occurred at both times of day, but systolic blood pressure reductions were greater after morning exercise (-7±3 vs. -3±4 mmHg, P<0.05). Exercise decreased cardiac output only in the morning (-460±771 ml/min, P<0.05), while it decreased stroke volume similarly at both times of day and increased heart rate less in the morning than in the evening (+7±5 vs. +10±5 bpm, P<0.05). Only evening exercise increased sympathovagal balance (+1.5±1.6, P<0.05) and calf blood flow responses to reactive hyperemia (+120±179 vs. -70±188 U, P<0.05). In conclusion, PEH occurs after exercise conducted at both times of day, but the systolic hypotensive effect is greater after morning exercise when circadian variations are considered. This greater effect is accompanied by a reduction of cardiac output due to a smaller increase in heart rate and cardiac sympathovagal balance.