Moderate isometric exercises to lower systolic and diastolic blood pressure
During repetitive muscular activities such as jogging, swimming or cycling, the dilation of blood vessels in the muscles involved decreases the levels of systolic and diastolic blood pressure, increasing blood flow throughout the body.
The constant contracting and relaxing of the muscles helps push blood through the vessels to the periphery of the body and back to the heart. The increased blood flow during moderate exercise causes an increase in systolic blood pressure during the first few minutes of exercise, though diastolic blood pressure remains essentially unvaried.
Systolic blood pressure increases rapidly with an increase in cardiac output, which is normally around 5 liters per minute while resting. For example, a resting systolic blood pressure of 120mmHg will reach 180mmHg if cardiac output increases by a factor of three. Diastolic blood pressure, on the other hand, only increases by about 12% during maximum effort.
This response is similar between sedentary and active subjects. However, during maximum effort, systolic blood pressure can reach 200mmHg in healthy and fit individuals.
During exercises that require maximum effort, such as short sprints or long resistance running, and including strength exercises such as weight lifting, the change in blood pressure can be dramatic, as the muscle contraction can compress peripheral arteries, causing a very significant change in the resistance to blood flow. For this reason, dynamic (isotonic) exercises are recommended more than static (isometric) exercises.
The additional work done by the heart could be dangerous for those who already suffer from high blood pressure or heart disease. These individuals should consider a more moderate form of exercise.
Some interesting studies have been done on the ability of muscle tissue to absorb oxygen from the blood during exercise. The percentage of oxygen taken up naturally increases with exercise and during an increase of either systolic or diastolic blood pressure.
Isometric strength training (muscle contraction without movement of the articular head) causes a temporary increase in blood pressure, due to the compression of blood vessels caused by intense and static muscle contraction. Until today, isometric training has always been discouraged for those who suffer from hypertension. Several studies were recently published on the subject, including one by Baross AW, Wiles JD and Swaine IL called Effects of the intensity of leg isometric training on the vasculature of trained and untrained limbs and resting blood pressure in middle-aged men (one of the first studies published on the topic), published on September 9th 2012. It showed that three weekly sessions for eight weeks caused a significant reduction in resting systolic and diastolic blood pressure, compared to a control group that did not carry out any kind of training. The sessions consisted of four 2 minute sets of an isometric leg exercise with 2 minute breaks in between, where the individual held a squat position for the assigned time. Increasing the weight of the isometric exercise caused a greater blood pressure drop at the end of the eight weeks. The mechanism that causes this decrease in systolic blood pressure seems to be related to the stimulation of vasodilator agents (such as nitric oxide), stimulated by the temporary reduction in blood flow caused by the compression of blood vessels due to intense muscular contraction.
Scientific articles below:
- Factors influencing isometric exercise training-induced reductions in resting blood pressure. (Scand J Med Sci Sports. 2015 Apr;25(2):131-42)
- Isometric exercise training for blood pressure management: a systematic review and meta-analysis.
(Mayo Clin Proc. 2014 Mar;89(3):327-34) http://web.a.ebscohost.com/ehost/pdfviewer/pdfviewer?sid=d8c0711f-307c-4df7-8147-ad04db16e0a4%40sessionmgr4002&vid=1&hid=4204
- Effects of the intensity of leg isometric training on the vasculature of trained and untrained limbs and resting blood pressure in middle-aged men. (Int J Vasc Med. 2012;2012:964697) http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3443998/
- Effect of Isometric Handgrip Exercise Training on Resting Blood Pressure in Normal Healthy Adults (J Clin Diagn Res. 2014 Sep; 8(9)) http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4225874/