The Frank-Starling law of the heart states that stroke volume is proportional to .

end diastolic volume

Explanation:

The Frank-Starling Law states that the stroke volume of the left ventricle will increase as the left ventricular volume increases.

when you breathe in, or inhale, your diaphragm contracts (tightens) and moves downward. this increases the space in your chest cavity, into which your lungs expand. the intercostal muscles between your ribs also enlarge the chest cavity. they contract to pull your rib cage both upward and outward when you inhale.