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{{DISPLAYTITLE:Maximum Heart Rate (HRmax)}}[[File:HeartRateSimplified.pngsvg|right|thumb|500px|A simplified chart of heart rate against exercise intensity showing [[Maximum Heart Rate]], [[Heart Rate Reserve]], [[Resting Heart Rate]] , [[Orthostatic Heart Rate]], and [[Heart Rate Deflection]].]]Maximum heart rate (HR_max) is the fastest rate the heart is capable of beatingand it must be tested as it cannot be calculated. Like any [[Muscle|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. However, with prolonged exercise (>10 min) [[Heart Rate Drift]] will gradually increase the Maximum Heart Rate<ref name="Wingo-2005"/>. 

Maximum heart rate is measured by recording the heart rate while steadily increasing the exercise load. There will come a point where the exercise load increases, but the heart rate stays constant and this is the maximum heart rate. Obviously this test involves very high intensity exercise which by the very nature has some degree of risk. It is generally advised the maximum heart rate test is performed under medical supervision. However, athletes that are confident in their health will occasionally do an informal maximum heart rate test using the an ordinary [[Best Running Watch|heart rate monitor watch]]. After a good [[Warmup]], all that is needed is to start running a hard pace and rapidly increase the intensity to all out. The maximum heart rate recorded in is obviously the HR_max.If possible, use a heart rate monitor that will measure [[Heart Rate Variability]] and verify the quality of your recording using firstbeat.com athlete software (there's a free trial). This will ensure you are reading a true heart rate and not getting noise.

There are various formulas for calculating HR_max based on age. However these formulas are a statistical approximation, so the actual HR_max could vary significantly. An analogy would be estimating your weight from your height; you can get a value, but he could be out so far as to be worse than useless. A 2002 analysis concluded that '''"Currently, there is no acceptable method to estimate HR_max"'''<ref name="surp"/>.  {| class="wikitable" |- valign="top"|[[File:HRmaxAge.jpg|none|thumb|400px|Maximum heart rate against age<ref name="MaxCalc"/>.]]|[[File:MaxHR2.jpg|none|thumb|400px|Data of HRmax for 225 subjects, 4 to 33 years<ref name="surp"/>.]]|[[File:MaxHR3.jpg|none|thumb|400px|A subset of this the data for ages 11 to 33 years, n=196<ref name="surp"/>.]]|}The charts above chart below shows how the measured HR_max varies with age. There is an obvious correlation, but you can also see the huge variation from the average. If we consider the leftmost chart, at age 50 , the average HR_max is 173, but there are people in the study with an actual HR_max that is as low as 158 and as high as 200. If a 50 year old athlete is aiming to work out at 75% of HR_max, then the calculated HR_max would indicate that 130 BPM is the right intensity. If their actual HR_max is 158, then they are working out at 82% of HR_max, which is a lot higher. On the other hand, if their actual HR_max is 200, then they are working out at 65% of HR_max which is too low. This means that the calculated HR_max should not be used with extreme caution.[[File:HRmaxAge.jpg|none|thumb|300px|Maximum heart rate against age<ref name="MaxCalc"/>.]]=Does HR_max HRmax decline with age in athletes?=

 =Does HR_max HRmax vary by sport?=It is often suggested that HR_max varies with the mode of exercise. If you consider HR_max to be the highest [[Heart Rate]] that the heart is capable of achieving, then this makes no sense. However, some sports do not use sufficient amounts of muscle to max out the heart rate. If you consider an extreme example, doing bicep curls would not demand enough oxygen to raise the heart rate to HR_max. This means that sports like cycling, which use a smaller number of muscles than running, will not raise the heart rate to HR_max. However, there will be a highest heart rate for that sport, and using that value as HR_max may be useful as the sport specific HR_max will reflect how hard the working muscles are being used. So if you have a HR_max of 200 while running, but 180 while cycling, then it is appropriate to use a 'HR_max' of 180 for cycling activities. So exercising at 75% of HR_max would be 150 when running and 135 while cycling. The lower [[Heart Rate]] when cycling will reflect the fact that the heart and lungs are not working as hard when running as when cycling, but the active muscles should be performing at a similar level.  =What does HR_max HRmax mean? Is higher better?=

 =HR_maxHRmax, HR_rest HRrest and Heart Rate Reserve=