What is indicated by systolic blood pressure?

Systolic blood pressure is defined as the pressure in the arteries during the contraction of the heart's ventricles. When the heart contracts, it pumps blood into the arteries, creating a peak pressure known as systolic pressure. This value is typically recorded as the higher number in a blood pressure reading and is crucial for assessing how well the heart is functioning and how effectively blood is being circulated throughout the body.

Understanding the other choices clarifies why they are not correct. The pressure during heart relaxation corresponds to diastolic blood pressure, which measures the pressure in the arteries when the heart is at rest between beats. Pressure at rest would not specifically indicate blood pressure at any active phase of the cardiac cycle and would likely refer more generally to a baseline measurement. Average blood pressure over time would pertain to mean arterial pressure, which takes into account both systolic and diastolic pressures to provide an overall view, rather than focusing solely on the height of pressure during contraction.