Some of the blood pressure-lowering benefits of jogging may come from brain fluid jostling around inside the skull 鈥� and people might be able to get the same effect just by sitting in a chair that vibrates up and down. When the idea was put to the test in a small trial, those who used such a chair three times a week saw a benefit similar to that caused by starting blood pressure medication.
Exercise, such as jogging or brisk walking, has many health benefits, including boosting heart and lung capacity and building muscles. But it also produces physical forces on many parts of the body, including the brain, says at the National Rehabilitation Center for Persons with Disabilities in Tokorozawa, Japan.
Sawada鈥檚 team wondered if the physical shaking of the brain could be behind some of exercise鈥檚 benefits to blood pressure. Tests on rats that were genetically predisposed to get high blood pressure showed that when their heads were gently vibrated up and down while their bodies were held still, it caused a small fall in their blood pressure similar to if they were made to exercise.
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To see if the same effect happens in people, the researchers designed a padded chair that moves a person鈥檚 whole body up and down twice a second by about 3 centimetres, creating similar vertical motions of the head as would occur if they were jogging.
The team asked 30 volunteers with mildly high blood pressure to sit in the chair for half an hour, three times a week. After one month, there had been a fall of 9 millimetres of mercury (mmHg) in their systolic blood pressure and of 4mmHg in their diastolic blood pressure, on average.
One caveat with this study is that the strategy can鈥檛 be compared with a placebo version of the chair where the participants are unaware of whether they are getting the real or a dummy version, says Sawad. The researchers did ask some of the volunteers to sit in a stationary chair as a comparison, where there was no benefit seen, but they obviously knew they weren鈥檛 getting the real treatment.
To understand the mechanism behind this fall in blood pressure, cells called astrocytes were taken from a region in the rats鈥� brains that controls blood pressure. The animals that received the intervention had lower levels of a signalling molecule called angiotensin II type 1 receptor than were seen in those that hadn鈥檛 had the treatment. This molecule, present on the surface of astrocytes, is known to be involved in blood pressure regulation.
The effects on astrocytes might happen because the head movements cause fluid that bathes cells in the brain to slosh around, creating frictional forces, says Sawada. 鈥淭he brain is not a solid body, it is like a sponge. When the brain deforms a bit, then water moves around.鈥� However, it isn鈥檛 clear why fluid friction on astrocytes affects blood pressure.
If the jogging chair shows the same benefits in larger trials, Sawada hopes it could be used in hospitals and nursing homes by older people who are too frail to jog.
at the says the study shows that part of the blood pressure-lowering effect from physical activity may be due to head movements. 鈥淲hile this is a very interesting finding, the studies were short-term, and the benefits of exercise are, of course, not limited to its effect on blood pressure.鈥�
Nature Biomedical Engineering
