Final answer:
The assertion that trainability is dependent on exercise stimulus is true, with genetic differences and muscle fiber composition influencing individual responses to exercise. The heart is made of cardiac muscle, not smooth muscle, and sprinting is an anaerobic activity that necessitates oxygen levels beyond what is readily available.
Step-by-step explanation:
The key point from the article titled "Concepts about Vo2max and Trainability Are Context Dependent" suggests that trainability may depend on the training stimulus or dose of exercise is true. This supports the understanding that individuals respond differently to exercise due to various factors such as genetic differences, as well as differences in muscle fiber composition. For instance, those with more fast-twitch fibers might respond better to anaerobic exercises, such as sprinting, and build stronger, larger muscles, while individuals with more slow-twitch fibers may benefit more from aerobic exercises and develop better endurance.
Regarding the other questions, it is false that the heart consists of smooth muscle tissue; in reality, it is predominantly made up of cardiac muscle tissue. It is true that sprinting is considered an anaerobic exercise, as it involves short, intense bursts of activity where the body's demand for oxygen surpasses the oxygen supply available.
Exercise also causes various physiological responses, such as changes in respiratory functions. For example, hyperpnea, which is an increased rate and depth of breathing, occurs immediately at the onset of exercise to meet the body's heightened oxygen demand. Similarly, the body will adapt to regular exercise by increasing the efficiency of oxygen utilization and possibly increasing the number of circulating erythrocytes with sustained exposure to challenges such as high altitude.