Answer:
a) Training can lead to an increase in the size and strength of the heart muscles, specifically the left ventricle, which is responsible for pumping oxygenated blood to the body. This effect is known as cardiac hypertrophy, and it can lead to a decrease in resting heart rate and an increase in the heart's stroke volume, or the amount of blood pumped per heartbeat.
b) This change in the heart muscles can improve an athlete's performance because a larger left ventricle with increased strength can pump more blood with each contraction, delivering more oxygen and nutrients to the working muscles during exercise. Additionally, the decreased resting heart rate indicates that the heart is working more efficiently, which allows the athlete to maintain a higher intensity of exercise for a longer period of time without experiencing fatigue.
c) When running, an athlete's muscles require more oxygen to produce energy than when at rest. To meet this increased demand for oxygen, the athlete breathes more quickly and takes larger breaths. The lungs take in more oxygen, which diffuses into the bloodstream and is transported to the working muscles. Additionally, the increased breathing rate helps to remove carbon dioxide, a byproduct of cellular respiration, from the body. This helps to regulate the pH of the body fluids and prevent respiratory acidosis, which can impair the body's ability to perform at high intensities. Overall, the increased breathing rate and depth during running help to support the athlete's energy needs during exercise