Endurance training leads to significant drops in vascular resistance and diastolic blood pressure

A new Finnish study shows that months of marathon training can lower peripheral blood pressure and vascular resistance, unveiling exercise’s real impact on the heart and circulation.

Study: Eight months of marathon school training reduced blood pressure, systemic vascular resistance and extracellular water volume. Image Credit: Rocksweeper / Shutterstock

Eight months of marathon training is associated with improved blood pressure, linked to reductions in systemic vascular resistance and extracellular water volume, providing new insights from researchers at the University of Tampere, Finland. The findings are published in the journal Scientific Reports.

Background

Cardiovascular disease is a leading cause of morbidity and mortality worldwide. High blood pressure is one of the major cardiovascular risk factors that can potentially increase the risk of mortality.

Regular physical activity is considered a potential non-pharmacological intervention to reduce blood pressure in primary hypertension. Both endurance and resistance training have moderately reduced blood pressure in individuals with normal or elevated blood pressure (hypertension).

Acute aerobic exercise is known to reduce blood pressure for several hours following exercise. However, it remains largely unknown to what extent this temporary reduction in blood pressure benefits long-term cardiovascular outcomes. The exact dose-response relationship between the intensity and duration of exercise and the assumed reduction in cardiovascular disease risk remains unclear.

In the current study, researchers examined the impact of an 8-month marathon school training on blood pressure and other vital hemodynamics, including heart rate, cardiac output, systemic vascular resistance, arterial stiffness, and extracellular water volume.

Study design

The study involved 45 individuals from a professionally instructed marathon school and 43 age- and sex-matched untrained individuals as controls. Four participants from the marathon school dropped out during the study and were excluded from the final analysis.

All hemodynamic parameters of participants were recorded before and after the 8-month marathon training initially in supine position and subsequently in passive head-up tilt position (passively moving a person to an upright position using a tilting bed).

The passive head-up tilt position was considered in the study, as blood flows to the lower extremities in an upright position, leading to a reduction in cardiac output. These changes in hemodynamics activate the sympathetic nervous system, which subsequently increases heart rate and systemic vascular resistance to maintain blood pressure. An increase in systolic blood pressure in response to standing is considered an independent predictor of adverse cardiovascular events.

Study findings

The study reported significant cardiovascular health benefits of 8-month marathon training, comprising 214 minutes of weekly exercise during the initial six months and 26-km-long running exercises during the last three months.

The participants in the marathon group exhibited a reduction in body weight, fat percentage, and body mass index (BMI) and an induction in maximal oxygen uptake and insulin sensitivity compared to control group participants.

In response to passive head-up tilt, both groups exhibited a similar decrease in systolic blood pressure and an increase in diastolic blood pressure at the beginning and at the end of the study. The comparison between the groups done at the end of the study revealed that final blood pressure values were significantly lower in the marathon group, with the reduction in finger diastolic blood pressure being particularly pronounced when comparing the change between groups. This was accompanied by significant reductions in systemic vascular resistance and extracellular water volume in the marathon group.

Study significance

The study reveals that aerobic endurance exercise (marathon) training can moderately improve peripheral diastolic blood pressure, a finding associated with reductions in systemic vascular resistance and extracellular water volume. The inclusion of an instructor-escorted marathon training is the major strength of the study, ensuring high-level adherence to the training program.

The study finds that the change in aortic blood pressure over the study period was not significantly different between the marathon and control groups. However, the researchers explain that the observed changes in aortic blood pressure could reach statistical significance with a larger sample size, which would increase statistical power and reduce variability. It is also important to note that the final aortic blood pressure values at the end of the eight months were significantly lower in those who underwent marathon training compared to controls.

From a physiological point of view, the researchers explain that the observed differences in blood pressure measured at the aortic and finger levels might be due to differences in vascular compliance and wave reflection. Alterations in thermoregulation might also explain the observed difference. In response to heat, blood flow in the fingers can increase by up to fivefold to remove excess heat through vasodilation. Regular marathon training is expected to induce changes in thermoregulation.

The observed reduction in blood pressure is accompanied by a reduction in extracellular water volume, which accounts for 35–45% of the total body water. A reduction in extracellular water volume can reduce blood pressure by reducing blood volume. As mentioned by the researchers, this finding may be related to the impact of long-term training on sodium balance, as endurance training is known to cause sodium loss due to sweating in athletes. Notably, the study also found no significant changes in arterial stiffness (as measured by pulse wave velocity), or in heart rate or cardiac output within the marathon group over the study period. These findings help to pinpoint that the observed blood pressure improvements were primarily linked to the reductions in systemic vascular resistance and extracellular water volume, rather than changes in large artery stiffness or overall cardiac output.

The study followed a voluntary participation approach, which may introduce selection bias. Furthermore, control group participants were not evaluated for aerobic and anaerobic thresholds at the end of the study. Regarding medication use, a more prevalent use of an estrogen-progestin combination was observed among control group participants, which might have influenced the findings.

Despite these limitations, the study findings support the role of regular exercise as a moderate, non-pharmacological intervention for reducing blood pressure and improving cardiovascular health.