Sciences of Sport | Resistance training and high blood pressure ...

Resistance training and high blood pressure: Lifting heavier is good for your health
According to the World Health Organization (WHO), heart disease causes about 18 million deaths each year worldwide. This is almost one third of all
deaths worldwide. In the European Union, 49 million people live with cardiovascular disease. Each year, about 1.8 million people die from these
diseases, which represents about 37% of the mortality. High blood pressure is responsible for almost half of these deaths, or 13% of deaths worldwide,
and more than 8 million deaths per year. The WHO estimates that by 2025, 1.56 billion people will have high blood pressure. Increased blood pressure
is an important risk factor for cardiovascular disease, including stroke and coronary heart disease.
Blood pressure is quantified by two values, systolic (maximum pressure in the systemic circulation when blood is ejected from the heart) and diastolic
(minimum pressure in the systemic circulation when the heart "relaxes"). For most adults, a normal blood pressure is 100-130/60-80 mmHg. But when
these values exceed 130/80 mmHg at rest on a daily basis, it is called hypertension. Many factors influence systolic and diastolic blood pressure,
including blood volume, arterial wall compliance, and peripheral resistance. While certain genetic factors and diseases can lead to hypertension,
the main cause is often behavioral: diet, alcohol consumption, smoking, sedentary lifestyle, etc.
In addition to pharmacological treatments, physical activity ("cardio" or resistance training) is often recommended for the prevention, treatment
and control of hypertension. It allows to improve different muscular functions and cardiovascular functions (including endothelial function) which
allow consequently to decrease blood pressure. And the clinical effects of
training are as good as or better than those obtained with drug treatments.
Current official recommendations include moderate to high intensity strength training (50-80% of 1RM), targeting the major muscle groups, at least
twice a week. However, most meta-analyses mix studies that include people with and without hypertension. In addition, no meta-analysis to date has
considered the load, volume, or workout frequency. Thus, resistance training is beneficial for lowering blood pressure, but since resistance training
protocols are extremely variable, how do we know the impact of load intensity or training frequency on hypertension?
The Study
In an attempt to answer this question, a Japanese researcher from Osaka University conducted a meta-analysis that included only randomized
controlled studies that lasted at least 7 weeks and in which the participants had high blood pressure, were overweight, and strength-trained
without any other intervention (diet, supplementation, medication, or lifestyle changes). Systolic and diastolic blood pressure and body mass
index were measured at the beginning and end of the protocol.
The author analyzed the results of 17 studies involving 646 people (including 322 women), aged 21 to 70 years. Of these participants, 352 were
in the training group and 294 in the control group. The interventions lasted from 8 to 34 weeks. The loads used ranged from 30 to 90% of 1RM,
over 2 to 6 sets of 8 to 20 repetitions, with 1 to 4 sessions per week.
Results & Analyzes
The main results of this meta-analysis show that blood pressure in hypertensive and overweight individuals decreases with resistance
training. On average, the decrease in systolic blood pressure was -4.7 mmHg (-6.7 to -2.8 mmHg) and the decrease in diastolic blood
pressure was -3.5 mmHg (-4.9 to -2.1 mmHg). However, these results are very heterogeneous from one study to another.
But when the researcher took into account the specifics of the training programs, it turned out that the intensity of the 1RM was
associated with the decrease in systolic blood pressure: the greater the percentage of 1RM (thus the heavier the load) and the
greater the decrease in blood pressure. And the statistical heterogeneity of the results disappeared. By performing a simple linear
regression, the researcher shows that at 50% of 1RM, the decrease in systolic blood pressure is estimated to be -1.7 mmHg, whereas
at 80% of 1RM, it would be -9.2 mmHg.
In addition, no decrease in body mass index was observed. This reinforces the hypothesis that the decrease in blood pressure in
hypertensive individuals was primarily caused by resistance training.
There are several possible reasons for the decrease in blood pressure. First, strength training is thought to improve vascular
function, particularly through improved blood vessel dilation. However, the literature has difficulty in agreeing on this point
because of differences in protocols and the mixing of studies with hypertensive and normotensive individuals in the meta-analyses.
The decrease in blood pressure could also be due to the impact of weight training on insulin sensitivity, but again, some studies
show a positive impact and others none.
Practical Applications
While at first glance, resistance training may not seem like an obvious solution to high blood pressure, it is nevertheless
very effective. And this meta-analysis highlights the role of intensity: lifting heavier will result in a greater decrease
in systolic blood pressure. Of course, there are still many points to be elucidated and for that, future studies on the subject
will have to agree on protocols including only people suffering from hypertension and the variables of the training programs
will have to be standardized. Coupling strength training with cardiovascular activity will prove to be even more beneficial
since the effects on cardiovascular, muscular, bone and metabolic health are no longer in question.
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