gth. However, there may be an increase in myofibrils, but no significant increase in muscle fibers. Evidence has shown that fast-twitch fibers take on oxidative capabilities and assume the properties of slow-twitch fibers. Long distance runners have as much as eighty- percent slow-twitch fibers. Training also causes an increase in the ability of fast-twitch fibers to utilize oxygen. Endurance training also affects cardiac performance. The most obvious change that training brings about is a decrease in heart rate at both resting and at a fixed intensity. The stroke volume at all levels of physical activity is increased. The leads to a decrease in blood pressure. There is also an increase in cardiac output; cardiac output is the primary determinant of oxygen transport.Respiratory performance is affected by endurance training. It increases the endurance of chest muscles, which minimizes the loss of respiratory performance. Training also reduces the time it takes to reach a steady breathing rate once the exercise has begun. The ventilatory demands are decreased for four reasons:1) Increase in muscular efficiency2) Decrease in ventilatory drive3) Reduction in sensitivity of carotid chemorecptors4) Lesser production of lactateEndurance training can cause changes in your endocrine/hormonal system. Studies have shown the adrenal glands, which secrete epinephrine (adrenaline), enlarge with training. Epinephrine, cortisol, thyroxine, glucagon, and growth hormones are all secreted during exercise. Epinephrine and growth hormones are involved in the mobilization of fat. The need for insulin, which is usually secreted after a meal, is lowered because the muscles can take up sugar during exercise. Overall, training seems to fine tune the body’s secretion and response to hormones. This leads to a more efficient use of hormones and energy.The previous talks about what endurance training does to your body. Now let’s look ...
