⚡🍎💪🥦People exercise for four purposes: to lose weight, increase flexibility, increase muscle mass, and train cardiopulmonary function. Of these four goals, the most important one is health: training cardiopulmonary function. Cardiopulmonary function, translated into the language of science and engineering, is equivalent to the "displacement" of a car. A car with a displacement of 5.0 is better than a car with a displacement of 1.6 on the highway. It has better performance and is easier to handle. By the same token, the better the cardiopulmonary function, the easier it is to manage a day's work. Train your heart and lungs, and you can of course run and swim. This is all a good way. But for people with extremely small time granularity, running and swimming are too inefficient. then what should we do? I did a lot of research, I also consulted a lot of experts, and finally chose a more efficient exercise method from the perspective of training cardiopulmonary function: skipping rope. Jumping for 5 minutes is equivalent to jogging for half an hour. And with the correct posture, skipping rope hurts only one-seventh of the knee. So I have a skipping rope in my home, office, and suitcase.