Exercise is great for improving heart health. But the thought of hitting the gym or going for a jog might put some people off from doing it. And, if you have a heart condition already, such dynamic exercises may not be safe to do.
The good news is, you don't necessarily need to do a vigorous workout to see heart benefits. You can even improve your heart health by holding still and trying really hard not to move.
Isometric training, as this is called, is becoming increasingly popular as a way of reducing blood pressure and hypertension, and improving strength and muscle stability.
Normally, to build strength and force, our muscles need to change length throughout a movement. Squats and bicep curls are good examples of exercises that cause the muscle to change length throughout the movement.
But isometric training involves simply contracting your muscles, which generates force without needing to move your joints. The harder a muscle is contracted, the more forceful it becomes (and the more forceful a muscle is, the more powerfully we can perform a movement).
If you add weight to an isometric exercise, it causes the muscle to contract even harder. A wall sit and a plank are examples of isometric contractions.
Isometric exercises are associated with a high degree of "neural recruitment", because of the need to maintain the contraction. This means these exercises are good at engaging specialized neurons in our brain and spinal cord, which play an important role in all the movements we do—both voluntary and involuntary. The greater this level of neural activation, the more muscle fibers are recruited—and the more force generated. As a result, this can lead to strength gains.
Isometric exercises have long been of interest to strength and power athletes as a means of preparing their muscles to generate high forces by activating them. But research also shows isometric exercises are beneficial for other areas of our health—including reducing hypertension and promoting better blood flow.
There are a couple reasons why isometric exercises are so good for the heart.
When a muscle is contracted, it expands its size. This causes it to compress the blood vessels supplying this muscle, reducing blood flow and raising the blood pressure in our arteries—a mechanism known as the "pressor reflex".
Then, once the contraction is relaxed, a sudden surge of blood flows into the blood vessels and muscle. This influx of blood brings more oxygen and (crucially) nitric oxide into the blood vessels—causing them to widen. This in turn reduces blood pressure. Over time, this action will reduce stiffness of the arteries, which may lower blood pressure.
When blood flow is reduced during an isometric movement, it also reduces the amount of available oxygen that cells need to function. This triggers the release of metabolites, such as hydrogen ions and lactate, which stimulate the sympathetic nervous system—which controls our "fight of flight" response. In the short term, this leads to an increase in blood pressure.
But when an isometric exercise is done repeatedly over many weeks, there's a reduction in sympathetic nervous system activity. This means blood pressure is lowered and there's less strain on the cardiovascular system—which makes these exercises good for the heart.
How to use isometric exercise
You can start by doing this four times a day, three-to-five times per week—focusing on the same exercise. As you progress, you can start to vary the exercises you do, add weights to the exercise, or add in more than one isometric exercise.
Some good isometric exercises to begin with include a static squat, a wall sit or a plank. Even during these small bouts of exercise, your heart rate, breathing and arterial pressure will all increase—the same responses that occur during more conventional whole-body exercises, such as cycling and running.
The beneficial improvements in blood pressure start to manifest around 4-10 weeks after starting isometric training—though this depends on a person's health and fitness levels when starting out.
Isometric training appears to be a simple, low-intensity mode of exercise that offers big benefits for cardiovascular health—all while requiring little time commitment compared with other workouts.
