Your body constantly adapts to the stresses under which you place it. Exercise is one such stress. Over time, your body will physiologically adapt to aerobic training. These physiological adaptations will decrease muscle soreness and make your heart more efficient so you can exercise more easily and at a higher intensity than when you first start a workout routine. More importantly, your overall health will improve.
Oxygen Transport
When you exercise, your muscles require more oxygen in relation to the intensity of the exercise. Oxygen delivery depend on your heart efficiently pumping blood to the muscles. With aerobic training your heart, because it is a muscle, increases in size. Consequently, more blood enters the heart, resulting in more blood pumped out to your body with each beat. This increase in blood flow leads to an increase in oxygen to the working muscles. An increase in oxygen transport to the working muscles enables your muscles to exercise longer before fatiguing.
Heart Rate
With aerobic training, your resting heart rate will decrease. Average heart rate is between 60 and 80 beats per minute. If your heart rate is 80 beats per minute, after 10 weeks of endurance training, this can be lowered to 70 beats per minute, or one beat per minute each week of training. A trained heart is a more efficient heart. Furthermore, your exercising heart rate also will decrease, enabling you to exercise longer or at a higher intensity.
Blood Volume
Blood volume increases with aerobic training via increased plasma volume. Immediately after a workout, you have higher levels of protein in your blood plasma. With repeated exercise, your body synthesizes new proteins. The increased protein attracts more fluid, thereby augmenting your plasma volume. Additionally, exercise causes your kidneys to retain more water and sodium, which also increases plasma volume. When the ratio of your plasma to your cells is increased, your blood is thinner. According to Harvard Medical School, thinner blood flows easily through your veins and arteries and is less likely to form blood clots compared with more viscous blood.
Muscle Fiber Type
Your muscles can be comprised of Type I or Type II fibers. Type I fibers are suitable for endurance exercise because they do not contract as quickly, but they also do not fatigue as quickly. By contrast, Type II fibers are suitable for sprinting exercise because they contract rapidly, but also fatigue rapidly. With aerobic training, Type I muscle fibers increase in size. This means your muscle fibers are able to contract for a longer period of time.
References
- "Physiology of Sport and Exercise," Jack H. Wilmore; 2008.
- "Medicine and Science in Sports and Exercise;" M.N. Sawka; February 2000.
- Harvard Medical School Family Health Guide; Is Blood Like Your Waistline --- the Thinner, the Better?
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