Intense interval exercise lowers blood sugar more effectively than intense continuous exercise, according to a study from Spain (Int J Sports Med, published online November 6, 2014). The study shows that interval training lowers blood sugar levels by making cells more sensitive to insulin. This means that not only is interval training necessary to compete in sports, it also may be the most effective way for exercise to prevent disease and prolong life. Forty percent of North Americans have high blood sugar levels that can damage every cell in their bodies to cause heart attacks, certain cancers, dementia, impotence, nerve damage and premature death.
You go into greater oxygen debt with interval training compared to intense continuous training. Extensive data show that lowering oxygen concentration in the bloodstream (intermittent hypoxia) is an effective treatment and prevention for many diseases, including diabetes, arteriosclerosis and heart attacks (American Journal of Physiology - Regulatory, Integrative and Comparative Physiology, November 15, 2014;307(10).
Study Results In the study from Spain, ten healthy young men were tested after:
• high-intensity intervals (4 all-out 30-second sprints),
• continuous 30 minutes of exercise at 46% of maximum effort, or
• continuous 30 minutes of exercise at 77% of maximum effort. All of the exercise treatments improved insulin sensitivity for more than 48 hours compared with resting, but the interval workouts had the highest improvement in insulin sensitivity. The authors feel that the intervals are more effective than continuous all-out exercise in making cells sensitive to insulin because it causes higher insulin levels and reduced use of fat for energy during and after exercise.
Other studies show that six 30-second bicycle sprints, done three times a week for two weeks increase insulin sensitivity (BMC Endocrine Disorders, January 28, 2009:9(3)). Interval training helps overweight people lose far more weight than continuous exercise (J Sports Med Phys Fitness, 2012 Jun;52(3):255-62 and Metabolism, 1994 Jul;43(7):814-8). Two weeks of high-intensity interval training burns more fat than continuous exercise in exercising women (J Appl Physiol (1985), 2007 Apr;102(4):1439-47).
What Is Interval Training? Intervals mean that you:
• exercise for a short period so intensely that you become short of breath,
• slow down long enough to recover your breath and slow your heart rate. Repeat the alternating intense bursts of exercise with slow recovery periods until your legs start to feel heavy and stiff. For example, a runner may run 12 very fast quarter mile repeats each followed by 110 yards of slow jogging. A cyclist may do 100 pedal strokes as fast as possible, followed by slow riding until he recovers his breath, repeated 30 times.
How does Interval Training Prevent Disease? When you do intervals, you usually exercise so intensely that you become very short of breath from lack of oxygen. It is the lack of oxygen, called oxygen debt, that protects you against a high rise in blood sugar that damages cells. When you exercise intensely continuously for an extended period of time, you cannot create as severe an oxygen debt as when you exercise intensely for a short time.
How Oxygen Debt Helps Your Body Control Blood Sugar Levels Your body converts food to energy by two major sources: 1) Anaerobic Glycolysis - Does Not Need Oxygen: Inside every cell but outside the mitochondria, your cells can convert sugar to energy without oxygen. 2) Krebs Cycle - Needs Oxygen: You have many tiny compartments called mitochondria in your cells that convert carbohydrates, fats and protein to energy, breaking down foods in a series of chemical reactions called the Krebs Cycle, to carbon dioxide and water. If you don't get enough oxygen, the chemical reactions slow down so much that lactic acid accumulates in your muscles and spills over into your bloodstream.
When you exercise so intensely that your blood levels of oxygen drop, the mitochondria suffer most from lack of oxygen, lactic acid accumulates and your body responds by enlarging and increasing the number of mitochondria and increasing the enzymes that are necessary to drive the many chemical reactions in the mitochondria that convert food to energy. This helps cells utilize carbohydrates, fats and proteins more effectively, which reduces the amount of sugar in cells and helps insulin drive sugar from the bloodstream into cells more rapidly and efficiently. Since high-intensity interval training causes a higher oxygen debt, it also increases the cells' ability to respond to insulin to drive sugar from the bloodstream into cells to lower high blood sugar levels more efficiently. See: How Increasing the Number of Mitochondria Makes You a Better Athlete Walk Faster, Live Longer Interval Training Strengthens Your Heart Types of Intervals
Caution: Intense exercise such as intervals can cause heart attacks in people who have blocked arteries leading to their hearts. Heart attacks that occur during exercise are far more likely to occur when a person starts a new exercise program or increases the speed or duration of exercise. If you have any question about your heart, check with your doctor before starting interval training.
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