A heart attack is caused by lack of oxygen. Anything that increases the supply of oxygen to the heart markedly reduces risk for suffering a heart attack, improves a heart attack victim’s chances of surviving a heart attack and of not having another heart attack, and makes him or her able to be far more active after a heart attack. People who have had heart attacks often have a markedly reduced ability to take in and use oxygen. A study published this month shows that interval training improves a heart attack victim's maximal ability to take in and use oxygen far more than continuous exercise does (J Cardiopulm Rehabil Prev, Feb 13, 2014).

A heart attack weakens the heart because it causes part of the heart muscle to die from lack of oxygen. Interval training builds up oxygen debts that stimulate the heart muscle to become much stronger than it would be by just exercising at a lesser intensity continuously (Circulation, 2007;115:3086-3094). One of the strongest risk factors for heart attacks is having diabetes or being pre-diabetic. Interval training is far more effective than continuous exercise in lowering all the factors that make a person susceptible for diabetes: high blood sugar, high fasting insulin or having sugar stuck on cells (Circulation, 2008;118:346-354):

What is Interval Training?
Interval training means not to exercise at a constant pace. It means to alternate slow movements with very fast movements at a fixed pace for a fixed time until a person's muscles feel heavy or hurt. For example, a runner may run 20 repetitions of 220 yards trying to average 32 seconds with each run followed by very slow jogging usually until he recovers his breath. A bicycle rider may do an interval workout in the middle of a ride that includes 20 repeats of 100 pedal strokes at a pace fast enough to make him short of breath, with each burst followed by slowing down enough to recover his breath.

Why Interval Training Helps in Competition
People who compete in sports requiring speed and endurance use interval training to improve performance. The limiting factor to how fast an athlete can move over distance is the time it takes to bring oxygen into muscles. The faster you can bring oxygen into your muscles, the faster you can move. When you can't meet your needs for oxygen, muscles start to burn and hurt and you have to slow down. Interval training is far more effective than continuous exercise to increase your maximal ability to take in and use oxygen.

Precautions for Interval Training
Since the intensity of the short bursts of exercise during interval training is far greater than during continuous exercise, greater stress is put on the heart. This could cause irregular heart beats or even a heart attack in people with blocked arteries or weakened hearts. Therefore, check with your doctor before you attempt this more intense form of exercise. The person most likely to suffer a heart attack during exercise is the one who has just started to exercise, or has just increased the intensity or duration of his exercise program. In the studies of interval training for heart attack victims, the training program was conducted under supervision in a medical facility.

How to Begin Interval Training
Jog or walk slowly for 10 minutes of warm up.
Then pick up the pace for either 10 seconds or 50 steps,
slow down, and pick up the pace again when you feel like it.


Pedal your bike for 10 minutes warmup.
Then pick up the pace for 50 pedal strokes.
Slow down until you feel ready to start your next interval and repeat the short bursts until your legs start to feel heavy or hurt or you feel uncomfortable.


Pick your favorite aerobic exercise machine or sport.
Warm up for 10 minutes, then pick up the pace for 10-30 seconds, then slow down again.
Repeat the intervals until you feel tired or sore, then quit for the day.

How long you rest between the intense intervals is not important to athletes and is not important to you. The main benefit comes from the intense bursts.

More at:
Short Intervals are Best
Interval Training for Sports

Checked 1/26/19