Final answer:
Endurance training enhances cardiac efficiency and muscular endurance, primarily through adapting slow-twitch muscle fibers to become more efficient at oxygen use and aerobic metabolism.
Step-by-step explanation:
Endurance training increases cardiac efficiency at rest and during submaximal and maximal exercise. Endurance exercises, such as aerobic activities, enhance the performance of your heart and muscles by making them more efficient in using oxygen. One's cardiovascular endurance benefits greatly from aerobic exercises like cycling and brisk walking, which mostly utilize slow-twitch muscle fibers. These fibers support more prolonged activity due to their higher content of capillaries, mitochondria, and myoglobin, enabling better oxygen transportation and sustainability of aerobic activities.
Skeletal muscle adaptations through endurance training include an increase in the number of mitochondria and myofibrils, leading to enhanced aerobic metabolism and ATP production. Unlike resistance training which generally focuses on muscle hypertrophy via the growth of fast-twitch muscle fibers and connective tissue, endurance training emphasizes improvements in muscular endurance and the structural efficiency of slow-twitch fibers.
It's also important to note that genetic differences contribute to varying responses to endurance training, with some individuals experiencing significant improvements in endurance, while others may show minimal changes. However, consistent endurance training will likely increase one's cardiac reserve—the difference between maximum and resting cardiac output (CO)—thus improving overall heart rate (HR) efficiency during exercise and at rest.