The instructor tells us to slow down if our pulse is too fast. But for me, it doesn't seem to matter. My pulse usually remains high. It would be helpful to know what your normal resting pulse is to compare with your heart rate during exercise. The harder a person exercises, the faster the heart beats and the stronger the heart muscle becomes.
Heart rate is determined by how hard the skeletal muscles contract.
When a person starts to exercise, the skeletal muscles contract and squeeze the veins near them, forcing blood toward the heart. When the skeletal muscles relax, these veins fill with blood. The alternating contraction and relaxation of skeletal muscles serve as a second heart, pumping extra blood to the heart. Measuring the heart rate isn't necessary as long as a person begins exercising slowly and increases the intensity gradually. The intensity should be increased until it is difficult to exercise and talk at the same time.