Final answer:
High responders to endurance exercise training may see up to a 50% improvement in VO2 max from prolonged and intense training, attributed to physiological and genetic factors influencing muscle fiber composition and cardiovascular capacity.
Step-by-step explanation:
High responders to endurance exercise training, that is individuals who achieve substantial increases in VO2 max, can experience up to a 50% improvement following a prolonged and intense training program. The VO2 max is an indicator of aerobic capacity and cardiovascular fitness, representing the maximum amount of oxygen a person can utilize during intense exercise. This physiological response varies among individuals due to factors such as differences in muscle fiber types, with those possessing a higher proportion of slow-twitch fibers generally achieving greater endurance increases due to their muscle's ability to carry more oxygen and sustain aerobic activity longer.
Additionally, it is noted that cardiac output (CO) can dramatically increase due to aerobic exercise. For example, in healthy young individuals, the CO can rise to approximately 19.5 L/min, which is 4-5 times the resting rate. Well-trained cardiovascular athletes can increase this to even higher levels, with their peak performance CO reaching 7-8 times their resting rate.