Mean arterial pressure (MAP)

Mean arterial pressure (MAP) is the average blood pressure over a full heartbeat, called the cardiac cycle.^{1Haff and Triplett (eds.), Essentials of Strength Training and Conditioning, 4th ed., p. 134.} It is not simply the average of the systolic and diastolic numbers.^{2Schoenfeld and Snarr (eds.), NSCA’s Essentials of Personal Training, 3rd ed., p. 34.}

The reason is timing. The heart spends more time relaxing (diastole) than contracting (systole).^{3International Personal Trainer Academy, Certified Personal Trainer Textbook, p. 204.} So for most of each beat, pressure usually stays nearer the diastolic level.^{1Haff and Triplett (eds.), Essentials of Strength Training and Conditioning, 4th ed., p. 134.} That makes MAP usually lower than the plain average of the two numbers.^{1Haff and Triplett (eds.), Essentials of Strength Training and Conditioning, 4th ed., p. 134.}

To estimate MAP, find the gap between the systolic and diastolic numbers. Then add one-third of that gap to the diastolic number. The NSCA writes it as MAP = DBP + 0.333 × (SBP − DBP).^{2Schoenfeld and Snarr (eds.), NSCA’s Essentials of Personal Training, 3rd ed., p. 34.} Another NSCA text divides the gap by 3 instead, which gives nearly the same answer.^{1Haff and Triplett (eds.), Essentials of Strength Training and Conditioning, 4th ed., p. 134.} For a reading of 120/80 mmHg, the gap is 40. One-third of 40 is about 13, so MAP is about 93 mmHg.

MAP rises during exercise.^{4Schoenfeld and Snarr (eds.), NSCA’s Essentials of Personal Training, 3rd ed., p. 103.} It can also be found by multiplying cardiac output by total peripheral resistance, the resistance blood meets in the vessels.^{4Schoenfeld and Snarr (eds.), NSCA’s Essentials of Personal Training, 3rd ed., p. 103.} In a healthy heart, systolic pressure climbs with aerobic effort while diastolic pressure barely changes. As a result, MAP climbs in step with the effort.^{3International Personal Trainer Academy, Certified Personal Trainer Textbook, p. 204.}