Wall sits and blood pressure: what a new UK trial found

The wall sit is the exercise most of us remember from school PE: back against the wall, thighs burning, someone counting down. It's also one of the best-studied moves for blood pressure, and a new UK trial has looked at a question I get asked a lot. Once you've started, how often do you need to keep doing it?

What the researchers did

The trial, published in BMJ Open Sport & Exercise Medicine, was led by researchers at Canterbury Christ Church University, with colleagues from St Mary's University Twickenham, UCL and Keele. It was picked up by ScienceDaily at the end of October.

They recruited 100 adults with an average age of about 37. Their systolic blood pressure (the top number) was between 120 and 140, which counts as normal to high-normal, so nobody had hypertension. None took blood pressure medicine, none smoked, and all did less than 150 minutes of moderate activity a week.

Twenty people were a control group and carried on as normal. The other 80 did wall sits at home three times a week for four weeks: four holds, with two minutes' seated rest between each. A lab test set each person's knee angle so the effort pushed their heart rate into a set target zone, and they wore heart rate monitors to check it.

After four weeks, those 80 were split into four groups for another month: three sessions a week, two, one, or none.

What it found

After the first four weeks, systolic pressure was about 9.5 mmHg lower than in the control group, and diastolic (the bottom number) about 5.5 mmHg lower.

By week eight, how often people kept going made a difference:

• Three a week: the biggest drop, about 13.7 mmHg lower than at the start.
• Twice or once a week: about 6.5 to 7 mmHg lower than at the start, with no real difference between the two.
• Stopped: blood pressure drifted back to the point where it was no longer clearly different from the control group.

Only the three-a-week group kept the changes in other measures, such as resistance in the blood vessels and how the nervous system regulates heart rate and blood pressure. No harms were reported in any group.

The caveats

This is a well-run trial, but it's small and short. The maintenance phase lasted just four weeks, and the authors say longer studies are needed. People knew which group they were in. The knee angle was set in a lab, which isn't how most of us train. And because nobody had high blood pressure, it doesn't tell us how the results apply to people who do.

It does fit earlier evidence. A large review in 2023 pooled 270 trials and, as BBC News reported, found isometric training gave the biggest average fall in resting blood pressure of the exercise types compared. The British Heart Foundation pointed out that there were far fewer isometric studies than cardio or weights studies, and that every type of exercise helped. So treat the wall sit as a useful extra, not a replacement for walking, cycling or strength work.

How to do a wall sit safely

1. Stand with your back flat against a wall and your feet hip-width apart, roughly two feet (60cm) in front of you.
2. Slide down until your knees are bent. In the trial each person's angle was set for them, so you don't need thighs parallel to the floor; a shallower angle is fine to start.
3. Keep your knees in line with your toes and your weight through your heels.
4. Breathe steadily the whole time and don't hold your breath. As one of the 2023 review's authors told the BBC, "you must remember to breathe".
5. Start with 20 to 30 seconds, rest, and repeat. Build up over a few weeks. One of the 2023 review's authors suggested four two-minute holds with two minutes' rest, three times a week, as the BBC reported.

The last part of each hold should feel hard but steady. If you feel dizzy, get chest pain or feel unusually short of breath, stop. If your knees complain, go less deep, or try a bodyweight squat or glute bridge instead.

If you have high blood pressure, a heart condition, or you take blood pressure medicine, speak to your GP before you start, and never change your medicine on the back of a study. The NHS says high blood pressure usually has no symptoms, and many pharmacies offer free checks if you're 40 or over.

Fitting it into your week

Three short sessions a week slots in neatly alongside normal training. I'd tag the wall sits onto the end of a session, after split squats or before a plank, so you aren't relying on willpower to do them on their own. If you train three days a week, that's your three sessions sorted. It's different from cardio, which works on blood vessels in other ways, as our look at a review of 72 cardio trials explains.

If you'd like a plan and a workout log to track your holds week to week, you can try FitFitCity free for a week.