Amount of Exercise to reduce heart attack

Your daily half-hour exercise session might not be
enough to keep your heart healthy, according to a new
meta-analysis published in the journal Circulation .
After analyzing the exercise habits of almost 400,000
people from 12 studies, the researchers discovered that
those who followed the recommended guideline of
working out for 30 minutes a day only lowered their risk
for heart failure by 10 percent—what they described as
just a “modest” reduction.
But people who worked out for an hour cut their odds
almost 20 percent.
And those who found the time to sweat it out for two
hours a day? They slashed their risk by 35 percent.
That’s fantastic—if you have two hours a day to work
out. But in reality, it’s hard enough to find the time to
exercise each day, let alone for multiple hours in a row.
So here’s what you can do instead: Make your short
workouts harder. (For 6 week’s worth of high-intensity
interval routines that take only 30 minutes to do, try The
Anarchy Workout .)
While the researchers didn't specifically look at intensity
in the study, they believe performing 30 minutes of
intervals—like sprints—can be more effective in
protecting against heart failure than doing a moderate
workout—like a jog—for the same amount of time, says
lead study author Ambarish Pandey, M.D., a cardiology
fellow at the University of Texas Southwestern Medical
School.
Here’s why: Interval training—workouts that alternate
between high-intensity effort and lower-intensity effort—
causes your heart rate to stay up for short bouts of time
and then go back down over and over again.
This “up-and-down” format is what ultimately
strengthens your heart. That’s because it forces the
muscle to work harder than if it had to consistently
maintain the same steady beats per minute.
And at the end of the day, a strong heart is one of the
most important factors in decreasing your risk of heart
failure—which occurs when the muscle gets too weak to
pump enough blood through your body, says Men’s
Health cardiology advisor Prediman Krishan Shah, M.D.
What counts as “high intensity?” When rating your
perception of how hard you’re working on a scale of 1 to
10, a high-intensity movement generally clocks in at a 7
or higher, says Men’s Health fitness director BJ Gaddour,
C.S.C.S.
You should be working as hard or as fast as you possibly
can.
Another way to measure it: Your heart rate should hit
160 beats per minute or higher at the end of each work
interval, Gaddour says.
You don’t need to crank up the intensity every single
workout, though. Adding small amounts of moderate
exercise throughout the day—like taking extra walks
after lunch and dinner—will increase your training time
and decrease your risk of heart failure.
And if you can only swing 30 minutes of moderate
exercise?
Don’t think if you can’t do two hours or go all-out during
your training, you shouldn’t bother, Dr. Pandey says.
“The benefits of exercise are dose dependent, so
anything is better than nothing,”
While this particularly study only focused on heart
failure risk, other evidence shows that moderate
exercise is great for preventing coronary artery disease
(CAD)—the most common type of heart disease that
occurs when a blocked artery leads to a heart attack,
and can commonly lead to heart failure—by lowering
major risk factors like high blood pressure, obesity, and
high cholesterol, explains Dr. Shah.