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[[File:HeartRateSimplified.png|right|thumb|500px|A simplified chart of heart rate against exercise intensity showing Maximum Heart Rate, [[Heart Rate Reserve]], [[Resting Heart Rate]] and [[Heart Rate Deflection]].]]

Maximum heart rate (HR_max) is the fastest rate the heart is capable of beating and it must be tested as it cannot be calculated. Like any muscle there is a limit to how fast the heart can contract, and this limits how fast the heart can beat. This maximum heart rate is not a "safe limit", but a physiological limit. It is not possible to exercise and push your heart rate beyond its maximum; if you see your heart rate go higher than the previously recorded maximum all you're doing is redefining what the maximum value is.