A simple 30-minute task is believed to be more effective than moderate exercise at lowering blood pressure. A new study suggests taking a half an hour warm bath can boost circulation and lower blood pressure. It assessed the impact of hot water and moderate excercise on 25 obese and overweight adults aged between 45 and 70.

The participants, who were physically inactive and had resting blood pressure no higher than 140/90 mmHg and a resting heart rate under 100 beats per minute, were put through two sessions separated by at least 72 hours. One session saw them immersed in 40C water for 30 minutes while the second made them cycle on a stationary bike for half and hour.

As reported by the Independent, the researchers monitored their blood pressure, as well as heart rate and body temperature. They found that a warm bath caused a greater drop in blood pressure than moderate cycling over a 30 minute period. The researchers have stressed that baths can’t replace exercise. However, a warm bath does offer an alternative to people who struggle with “conventional exercise”. As well as lowering blood pressure, the study showed that hot water immersion can make blood vessels wider. This creates more space for blood to flow.

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

Scientists say that as you submerge your body in warm water, your body temperature rises which causes your blood vessels to relax. As they expand, they create more space for blood to flow which decreases vascular resistance and drops the pressure exerted against your artery walls.

Dr. Adolph Hutter, professor of medicine at Harvard Medical School, previously said: “The high temperatures in a warm tub or sauna cause your blood vessels to dilate, which lowers blood pressure.”

However, he warned that “people in their 70s and older whose blood pressure is on the low side also should be extra careful”. If the water is too hot in the bath, your blood pressure may dip too low, which can make you feel dizzy or lightheaded.

He explained: “A water temperature of 100F (37.7C) to 105F (40.5) is reasonable. Get in slowly, so your body can accommodate gradually.”