24. The top number of your blood pressure reading is called the systolic number.
Every time your heart beats, the blood that it pumps throughout your body press against the walls of your arteries. So if you had the idea that blood moves through your blood vessels the way water moves through a water hose, that image isn’t entirely accurate. Instead of there being a regular flow, there are contractions followed by relaxations. Each time your heart beats, it contracts in a motion known as systole. The systolic number of your blood pressure measures this force of blood against the arteries every time your heartbeats. Because this force is higher when your heart is beating, the systolic number represents the higher your blood pressure reading.
When you are exercising, your heart is contracting harder and faster to pump more blood so that it can replenish the supplies of oxygen and energy that are rapidly depleting. What happens then is your systolic blood pressure goes up, so taking a blood pressure reading right after exercise will indicate a higher rate than average. The best time to measure blood pressure is when you are resting because the reading you get will indicate how efficiently your heart usually is pumping blood. The number is in millimeters of mercury, or mmHg, based on the earliest instruments that doctors used to measure blood pressure. However, you don’t need to understand how old-fashioned medical equipment works; know that an ideal reading for your systolic blood pressure is between 100 and 120.