Which of the following best describes the long-term cardiovascular adaptation to prolonged aerobic training?

Long-term cardiovascular adaptation to prolonged aerobic training is best characterized by enhanced cardiac output. As an individual engages in aerobic training over an extended period, their heart becomes more efficient. This is typically indicated by an increase in stroke volume, which is the amount of blood ejected by the heart with each beat. Alongside this, the heart rate at rest and during submaximal exercise tends to decrease due to improved cardiac efficiency.

Additionally, aerobic training leads to structural changes in the heart, such as increased size of the left ventricle, allowing for greater blood volume to be pumped with each contraction. This results in an overall increase in cardiac output, which is crucial for delivering oxygen and nutrients to working muscles, particularly during sustained physical activity. As a result, individuals who undergo regular aerobic training often experience improved cardiovascular fitness and endurance.

In contrast, increased blood viscosity and arterial stiffness are not desirable adaptations and are generally associated with negative cardiovascular health outcomes or can occur with a sedentary lifestyle or certain medical conditions. Reduced ability to transport oxygen contradicts the physiological benefits of aerobic training, as one of the primary benefits is improved oxygen transport capacity due to enhanced red blood cell production and increased capillary density in muscles.