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.
Isometric exercises may be even more beneficial for heart
health than other types of cardiovascular exercise. A study which compared the
benefits of isometric exercise versus high-intensity interval training found
isometrics led to significantly greater reductions in resting blood pressure
over the study period of between two and 12 weeks.
How to use isometric exercise
If you want to use isometric training to reduce blood
pressure, it's recommended that you should do any isometric contraction for two
minutes at around 30-50% of your maximum effort. This is enough to trigger
physiological improvements.
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.
