Читать книгу HIIT Your Limit. High-Intensity Interval Training for Fat Loss, Cardio, and Full Body Health онлайн
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Another fascinating cardiorespiratory adaptation of the body—one well observed during HIIT workouts—can be seen in your muscles. Your muscles move your body and are fueled by incredible bean-shaped, energy-producing organelles known as “mitochondria.” Mitochondria are often referred to as the energy factories of your cells. Depending on a person’s training and genetics, each individual muscle cell may have four hundred to two thousand of these powerhouse mitochondria. With regular HIIT workouts, mitochondria get bigger and the body makes more of them in the muscle cells. Isn’t that amazing? This occurrence is seen in women and men of all ages, fitness levels, and ethnic backgrounds. Therefore, the size and number of mitochondria directly translates into enhanced cardiorespiratory fitness at any level of exercise intensity.
From a health perspective, this cardiorespiratory improvement is invaluable, because low aerobic fitness is directly linked to heart attack and other health-related causes of mortality. In a large, 1996 pioneering study at the famous Cooper Institute in Dallas, Texas, researchers studied the medical exams and cardiorespiratory tests of 25,341 men and 7,080 women. The results of this landmark study indicated that adults who are moderately or highly fit had enhanced cardioprotection. “Cardioprotection” is a relatively new term in science. It means those women and men who were fitter had better defenses against heart disease and heart attacks, compared to women and men who were less fit. This finding was found to be true regardless of whether the individuals were smokers or nonsmokers, had normal or elevated cholesterol levels, or were obese or had average body weights. Another prominent study, this one published in the American Journal of Cardiology in 2006, concurs with the results of the Cooper Institute investigation. In this study, the researchers found that vigorous exercise intensity was more beneficial (i.e., more cardioprotective) in positively altering one or more risk factors to heart disease.