Contractility describes the forcefulness of the heart's contraction. Increasing contractility reduces end-systolic volume, which results in a greater stroke volume and thus greater cardiac output.

What is increased contractility?

Increasing contractility is done primarily through increasing the influx of calcium or maintaining higher calcium levels in the cytosol of cardiac myocytes during an action potential.

What increases muscle contractility?

Short-term increases in demand on the heart (e.g., exercise) are met by increases in the force and frequency of contraction. These changes are mediated by increases in sympathetic nervous system activity, an increase in the frequency of contraction, and changes in muscle length.