Select the elliptical machine. First of all, elliptical machine is an aerobic fitness equipment, which can achieve the purpose of most people's daily exercise in exercise intensity. Secondly, elliptical machines are different from treadmills and spinning bikes. When people move on an elliptical machine, the trajectory is elliptical, and there is almost no focus when they step on it. The knee joint will not bear the pressure of several times the weight of a person like on a treadmill, and it can even be said that there is almost no pressure, so it does not hurt the knee.