A study published in the journal Blood Pressure Monitoring proves that the benefits of physical activity for hypertensive individuals can be enhanced if the exercises are practiced between 6 pm and 9 pm.
The analysis focused on the cardiac recovery rate (CRT), which, roughly speaking, can be explained as the measure of heart rate reduction after exercise interruption. Night training improved both the fast phase (measured 60 seconds after the peak of physical effort) and the slow phase (measured 300 seconds later) of CRT.
The investigation was conducted by the post-doctoral student Leandro Campos de Brito, under the guidance of Professor Cláudia Lúcia de Moraes Forjaz, from the School of Physical Education and Sport at the University of São Paulo (EEFE-USP). The researcher compared responses of hypertensive patients to structured aerobic training performed in the morning and at night for ten weeks.
According to Brito, approximately 25% of people do not respond to exercises from the point of view of pressure control, and for them, different strategies from conventional ones are needed. For example, exercising at times that can maximize the benefits.
Brito’s initial idea, in his doctorate, was to assess the chronic effect of exercise in terms of cardiovascular benefits in general. This also included CRT responses, as the measure of heart rate reduction after exercise cessation. It is a variable capable of providing a marker of the autonomic mechanisms that regulate the functioning of the heart.
“There are two branches in the cardiac autonomic system: the sympathetic and the parasympathetic. Roughly speaking, the parasympathetic makes the heart slow down, and the sympathetic makes the organ speed up and beat faster. It is expected that, after a period of training with physical exercises, the power of the parasympathetic will increase [coração mais relaxado] and the sympathetic one decreases. The CRT allows us to infer how this behavior occurs, through the measurement performed in the first 60 seconds [resposta tipicamente parassimpática] and 300 seconds after the end of a maximal cardiopulmonary effort test, with the latter response suggesting both the action of the parasympathetic nerve, recovering the heart beat, and the sympathetic deceleration, whose activity was accumulated during exercise”, he explains.
According to the group of scientists, the fact that both phases (fast and slow) of CRT have increased with night training indicates that exercising at this time of day improves both branches of the cardiac autonomic system (parasympathetic and sympathetic). Furthermore, the results show that the beneficial effect is not limited to when the volunteers exercised.
“We evaluated people in the morning and at night, and those who trained at night showed better results in both evaluations.”
The experiment involved 49 middle-aged hypertensive men, medicated for at least four months with the same type of drug and the same dosage. They were randomly allocated into three groups: morning training (7:00 am to 9:00 am), night training (6:00 pm to 9:00 pm) and the control group (no aerobic training).
Training was performed three times a week for ten weeks. The groups that performed the training pedaled on the ergometric bicycle (30 minutes in the first two weeks and 45 minutes in the others, with moderate intensity), and the control group did stretching (30 minutes). In the initial and final evaluations of the study, the heart recovery rate of the volunteers was measured 60 and 300 seconds after the end of the exercise.
“For the control group, we opted for an activity that would not bring additional benefit impact on the studied variable. That’s why this specific type of stretching [estático e ativo]. The objective was to make the control group go to EEFE-USP the same number of times as the group that trained, have the pressure measured the same number of times, meet the researchers on the same days, feel cared for in the same magnitude” , explains Brito, first author of the article.
The experiment was carried out at the Laboratory of Hemodynamics of Motor Activity at EEFE-USP, coordinated by Forjaz.
The study was supported by FAPESP, through a doctoral scholarship granted to Brito, who was also a Masters scholarship holder and is currently receiving a postdoctoral scholarship.
Researchers are trying to understand the mechanisms that make this improvement more expressive at night. In the first work, they found that baroreflex sensitivity (an autonomic mechanism that controls blood pressure, beat to beat) was increased with training.
“This mechanism assesses, each time your heart beats, whether the pressure has gone up or down too much, and corrects it. Such a more sensitive mechanism reflects better health. Evening and morning training improved the sensitivity of this mechanism, but evening training improved it more. However, it is a spontaneous measurement, taken with the person at rest. Currently, in the postdoctoral period, we do a maximum stimulation of this sensitivity using medications, which, somehow, ends up reflecting a little more the stress of everyday life, because no one is stationary all the time, the individual has physical and cognitive challenges and emotional in which this autonomic control is also required”, says Brito.
He explains that an individual’s cardiovascular functions vary 24 hours a day. “The expectation is that in the morning, when we wake up, our blood pressure value will increase, reaching a first peak around 10 am. So, this value stabilizes, and there will be a reduction in the middle of the afternoon, around 3:00 pm. A second peak happens between 18:00 and 20:00. After that, there is a progressive reduction, with both blood pressure and heart rate registering the lowest values ??around the middle of the night. We are proposing that this overnight exercise would be finding a window of opportunity for more significant improvement.”
According to Brito, at night, the individual has greater baroreflex sensitivity and less sympathetic activity. “Furthermore, because of the 24-hour cycle, at night it starts to have a reduced heartbeat and also has less resistance in the blood vessels. It’s a time when the stress on the cardiovascular system is lessened, and it appears that this allows exercise to have more benefits. It is a hypothesis to explain this result we found.”
Along with colleagues, he had already published other articles on the topic, such as the one published last year in the journal Clinical and Experimental Hypertension (read more at: agencia.fapesp.br/34212/).
The physical education professional emphasizes, however, that benefits were also registered in the group that trained in the morning, but with less intensity. “It’s important to say that when it comes to exercising, anytime is better than notime. In other words: it is necessary to exercise. What we tried in this work was to maximize the responses.”
According to Brito, resistant hypertensive patients, who take four or more antihypertensive drugs a day, need better strategies to address the problem than conventional ones. “For them, I think our results are very interesting.”
The scientist explains that everyone gets higher blood pressure as they get older, but not everyone will be hypertensive. “In adults, one in four is hypertensive; in the elderly, two out of three people are hypertensive.”
Brito points out that the minimum recommended for an adult is 150 minutes of moderate physical activity per week. “If you only do those 150 minutes, you already have a 7% lower risk of becoming hypertensive in maturity. And when I talk about physical activity, I’m encompassing all types of physical activity, including cleaning the house. If you are already hypertensive, if you follow this recommended minimum, you will have up to 50% lower risk of having complications from hypertension.”
The researcher reaffirms that physical activity, in general, confers an intense protective factor on blood pressure control. “If the hypertensive individual does a structured aerobic exercise, similar results will be expected, for example, those referring to the use of a hypertensive medication. No wonder, in the guidelines of the Brazilian Society of Hypertension [SBH], the first suggested intervention is a change in lifestyle, and not the use of medication, when the patient’s clinical condition allows”, reinforces Brito, who is also director of the physical education department at SBH. “No hypertensive person should go without aerobic exercise.”