In adults at risk of developing high blood pressure, or hypertension, a series of shorter bursts of activity may be more effective in keeping blood pressure in check than a single long exercise session, according to a study.

After four 10-minute sessions on a treadmill, spaced an hour apart, people’s blood pressures were reduced for three to four hours longer than after a single 40-minute treadmill workout, Dr. Saejong Park of Indiana University in Bloomington and colleagues found.

“Results of our study indicate that as few as four 10-minute walking sessions per day is effective in reducing blood pressure in prehypertension,” Park and his team conclude in a report in the Journal of Hypertension.

Prehypertension occurs when a person’s blood pressure is above normal but does not meet the definition of hypertension. For these individuals, 30 minutes of “moderately intense” exercise on most days of the week is the only currently recommended treatment.

To compare the effectiveness of several smaller exercise sessions or a single longer workout, the researchers had 20 people perform the four shorter exercise sessions and then, a week later, a single longer one, or vice versa.

After the single, longer workout, participants’ systolic and diastolic blood pressures were reduced for seven hours.

But after the series of shorter sessions, systolic blood pressure (the top number in a blood pressure reading) stayed low for 11 hours, and diastolic pressure remained low for 10 hours.

The shorter workouts compared to the single longer workout may have done better job of restoring the balance of the nerves that control how blood pressure responds to daily demands, the researchers suggest.

SOURCE: Journal of Hypertension, September 2006.