How do cellphones calculate heart rate?

What is the best way for a female to calculate their maximum heart rate?

• I was previously using the formula 220-age then I came across an article that said that newer research says for a female the best way to calculate it would be 202 - ( .88 x age). What do you use?

• Answer:

  The percent variable depends upon age and goal. For a girl, 200 minus age times the variable, which is the target. Another way to think of it is to work to capacity, stop and placing index finger on carotid artery, count the pulse for ten seconds. Multiply that by six to get beats per minute at maximum, like from running 200 yards as fast as possible or more to reach exhaustion. From that figure, decide what would be a good training pulse. If you work out so hard that you cannot carry on a conversation, figure that is the top workout rate. If it is desired to work out at a slower pace, such that a conversation could be carried out, that might be at 120 to 140 depending on the individual and fitness level. Getting back to your question and the equation, as follows with an example for a 20 year old at a target rate of 75%, which for someone not an elite athlete would be fine: 180 X 75% is 135. Anywhere around there upwards would be for a more fit individual and lower for a less fit person. Most people who are elite athletes do know their target rate, as that is part of their training regimen.