What does high intensity training actually mean?

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High intensity training means short-term training under maximum stress. A variety of systems, such as the circulatory system, heart, lungs, muscles, nerves, and your metabolism are challenged and stimulated in a most intense way. The so-called afterburn effect is particularly high during high intensity training, which means a long-term increase in energy consumption and metabolism. Heart rates of more than 90% of maximum efficiency are characteristic of high intensity training. Whether you are in this range during training, a heart rate monitor can easily tell you.