Answer:
because they can do some things and harm you
Explanation:
Ans. Contractility. It is defined as the intrinsic ability of the heart muscle to contract. An Anrep effect happens when there is an increase in contractility due to the activation of catecholamines. When this happens, it allows myocardium to compensate for an increase end-systolic volume and decreased stroke volume that occurs when aortic blood pressure increases.
Both are A, trainer would do the physical training and fitness specialist would show you the science.