Reductions in blood pressure may be maintained over the short term with just one or two sessions of isometric exercise training a week, suggest the findings of research published online in the journal BMJ Open Sport & Exercise Medicine.
Doing this form of exercise three times a week may maintain the benefits in blood pressure reduction over a longer period, the findings suggest.
For people unable to commit to training more often, just one session a week can help maintain significant health benefits, the researchers say.
Isometric exercise training involves holding a pose for a few minutes at a time. Examples include remaining in a squat, holding a plank, or hand grip exercise.
Previously published studies have shown that isometric exercise training reduces blood pressure more than other forms of exercise and can produce an effect similar to, or greater than, some drug treatments.
But it has not been established how frequently isometric exercise training has to take place in order to retain these benefits.
To find out, researchers recruited 100 adults with an average age of 37.4 years with normal to high-normal systolic blood pressure (120-140 mmHg) who did not regularly take structured exercise.
According to expert guidelines, 130-139 mmHg is classed as "high-normal" blood pressure and should trigger specific medical lifestyle advice but the study participants did not have hypertension.
Participants were only included in the study if they had no injuries or illnesses, were not taking and had not previously taken blood pressure medication, were not smokers and did not consume more than 14 units of alcohol per week.
The participants were randomly allocated to five groups—a control group and four groups who all followed the same initial four week home-based lower body isometric training exercise programme.
This programme comprised four bouts of isometric wall-squat exercise separated by two minutes of seated rest, three times a week.
For the following four weeks, the participants were split into four training schedules: one group continued to exercise three times a week, a second group twice a week, and a third group once a week. The remaining group stopped the exercises entirely.
Blood pressure, heart rate and other cardiac measurements were taken at the start of the study and after four and eight weeks.
Consistent with previous research, all the groups who did the initial four week exercise programme showed significant reductions in systolic blood pressure, diastolic blood pressure and mean arterial pressure after four weeks compared with the control group. Once the groups were separated at four weeks, there was no longer a statistical difference in diastolic blood pressure for any of the groups.
At eight weeks the groups who had done the exercises once or twice a week were able to maintain significant reductions in systolic blood pressure and mean arterial pressure, but not diastolic pressure, compared to the control group.
However, those who continued isometric exercise training three times a week maintained their blood pressure reductions and achieved the greatest reduction (-13.73 mmHg) in systolic blood pressure compared with the start of the study. This compares with a reduction of 6.95 mmHg for those in the twice a week group and 6.56 mmHg in the once a week group.
They also maintained improvements in other cardiac measures including total peripheral resistance (an indication that blood vessels have narrowed) and heart rate variability.
The group who had stopped doing the isometric exercises after the initial four week period showed a reversal of their blood pressure to levels not significantly different from the control group.
A limitation of the study is that the follow up period for the maintenance phase was only four weeks and longer term studies are needed.
"The study demonstrates that while lower frequency isometric exercise training may be sufficient to maintain blood pressure reductions over the short term, higher frequencies are required to preserve these benefits and the associated vascular and cardiac autonomic adaptations," the researchers write.
"The study offers evidence that lower frequency isometric exercise training can help maintain short-term blood pressure reductions, providing a pragmatic option for individuals with limited time or adherence challenges."
