The simple activity that can lower blood pressure better than moderate exercise

The simple activity that can lower blood pressure better than moderate exerciseTaking a 30-minute warm bath can boost circulation and lower blood pressure better than doing moderate physical activity like cycling, a new study suggests.

Previous research shows that tiny blood vessels under the skin play a key role in maintaining the body's core temperature and heart health. Known as microvessels, they help regulate the exchange of oxygen, nutrients and waste products as they deliver blood to tissues. These vessels also regulate temperature by widening and allowing more blood to flow near the surface of the skin when it becomes hot, helping release more heat into the environment.

Exercise enables this by improving the function of the endothelium, the thin layer of cells lining blood vessels.

But it's poorly understood how the body responds to passive heat, particularly in overweight and obese older adults, for whom exercise can be difficult.

The new study assessed the effects of hot water and moderate exercise on microvessels in 25 obese and overweight adults between the ages of 45 and 70.

A female patient having her blood pressure measured by a doctor (AFP via Getty)

The participants were physically inactive, doing less than 150 minutes of structured exercise per week, and had resting blood pressure no higher than 140/90 mmHg and a resting heart rate under 100 beats per minute.

They were put through two sessions in random order, separated by at least 72 hours. In the first session, they were immersed in 40C water for 30 minutes. In the other, they were made to cycle on a stationary bike for half an hour at moderate intensity, corresponding to 60–70 per cent of their maximum heart rate.

Researchers monitored the heart rate, body temperature and blood pressure of each participant through both sessions.

They also used a non-invasive technique called optical coherence tomography to produce detailed images of their tissues, allowing them to estimate the diameter of small blood vessels, the speed of blood moving through them, and the volume of the blood flow.

Customers relaxing in a hot bath at Koganeyu (AFP/Getty)

Researchers found that immersion in hot water caused immediate changes in blood vessels under the skin, making them wider and creating more space for blood to flow. A warm bath also caused a greater drop in blood pressure after 30 minutes than moderate cycling.

While hot baths can't replace exercise, researchers say, the study offers strategies for people who struggle with physical activity.

Repeated hot-water immersion can improve certain measures of blood vessel function and potentially complement conventional exercise programmes in sedentary adults.

"These data support further investigation of hot water immersion as a practical intervention," the study, published in the European Journal of Applied Physiology, said, "particularly for individuals with limited capacity for conventional exercise."