Aerobic exercise involves moving the largest muscles of your body in a rhythmic, repetitive pattern — think brisk walking, running, cycling, and swimming. It's long been considered the best type of activity to lower blood pressure. But growing evidence shows that strength training can also reduce blood pressure. According to a new study, the most effective type involves contracting your muscles without any movement, which is known as isometric or static exercise (see "Muscle-strengthening activity: Types, terms, and examples").
Published October 2023 in the British Journal of Sports Medicine, the study pooled findings from 270 clinical trials involving a total of more than 15,000 people. All the trials lasted at least two weeks and reported the effects of exercise on blood pressure. As expected, most types of exercise helped lower blood pressure. But the most effective workout, especially in people who had high blood pressure, was isometric exercise training.
"It's an interesting and somewhat provocative finding because of the historic focus on aerobic exercise for reducing blood pressure," says Dr. Timothy Churchill, a cardiologist at the Cardiovascular Performance Program at Harvard-affiliated Massachusetts General Hospital. Aerobic (which means "with oxygen") exercise boosts your heart rate and increases blood circulation to deliver oxygen throughout the body. The blood pressure benefits appear to stem from improvements in heart and blood vessel health.
Muscle-strengthening activity: Types, terms, and examples
Anything that makes your muscles work harder than usual counts as a muscle-strengthening activity — something all adults should aim to do at least two days a week, according to the federal Physical Activity Guidelines.
Often referred to as strength training, this type of exercise works by harnessing resistance — that is, an opposing force that muscles have to strain against. It's also known as resistance training or weight training. You can use many different things to supply resistance, including your own body weight, free weights such as dumbbells, elastic bands, or specialized machines. Other options include medicine balls, kettlebells, and weighted ropes.
Muscles can grow stronger by exerting force through these three actions:
Concentric. Muscles move joints while shortening. Think of what happens when you flex your arm to show off your upper arm (biceps) muscle. It's the same type of motion you would use when raising a dumbbell or lifting a bag of groceries off the counter.
Eccentric. Muscles move joints while lengthening. As you slowly lower a dumbbell or grocery bag, your biceps muscles lengthen while producing force to lower the object in a controlled manner rather than simply letting it drop.
Isometric. Muscles don't shorten or lengthen much, and joints do not move. If you push against a wall, for example, or try to lift an object that is far too heavy for you, your arm muscles will tense. But since your muscles can't generate enough force to lift the object or shift the wall, they stay in the same position instead of shortening.
Muscle-strengthening exercises that include both concentric and eccentric muscle movement is known as "dynamic" or "isotonic" strength training. Examples include push-ups, biceps curls, and squats. Examples of "isometric" or "static" strength training include doing wall squats (also called wall sits), planks, or an overhead hold.
Adding isometric exercise
The new findings add to the evidence that strength-based exercises are also good for cardiovascular health. But rather than taking priority over all other types of exercise, strength training should be incorporated into your overall routine, says Dr. Churchill. While isometric exercise — especially wall squats — appeared to lower blood pressure the most, the study authors were somewhat cautious about overselling that finding, given that relatively few studies (18 of the 270) included isometric exercise and none compared it directly against other forms of exercise.
Still, experts have speculated about a possible mechanism. During isometric exercise, clenched muscles temporarily constrain blood flow. The subsequent surge of blood may stimulate the release of factors that help relax the vessels and ultimately contribute to a reduction in blood pressure.
Isometric exercise has some additional advantages. Because you don't move your joints, isometrics can be easier and safer for people with joint injuries or diseases. Many of the exercises don't require any special equipment, and you can do them anywhere.
The physical activity guidelines don't specify how long to do muscle-building exercises. "But even just 10 to 15 minutes, two days a week, is a good place to start," says Dr. Churchill. Try doing some wall squats or a modified plank.
To do walk squats, stand with your back flat against a wall. Walk your feet about 18 inches from the wall, placing your feet shoulder-width apart. Tighten your abdominal muscles, then inhale and exhale as you slide your back down the wall until your thighs are as close to parallel as possible to the floor and your knees are above your ankles. Hold for 20 to 60 seconds. Slide slowly back up the wall to a standing position. Rest for 30 to 60 seconds, and repeat two times.
Exercise photo by Michael Carroll
Remember to breathe!
During any type of strength training, be careful not to hold your breath. Some people do this unintentionally, although others have a misguided belief that breath holding increases their effort and power. But breath holding during exertion can cause dangerous blood pressure spikes, says Dr. Churchill.
When you do dynamic strength training, exhale as you lift, push, or pull, and inhale as you release. When doing isometric strength training, take a big breath as you move into position. Then take shallow breaths as you hold the pose, and take regular full breaths during the rest and recovery phase.
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