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http://en.wikipedia.org/wiki/Heart_rate#Measuring_HRmax
Measuring HRmax
HRmax is the maximal safe heart rate for an individual.
The most accurate way of measuring HRmax is via a cardiac stress test. In such a test, the subject exercises while being monitored by an EKG. During the test, the intensity of exercise is periodically increased (if a treadmill is being used, through increase in speed or slope of the treadmill), continuing until certain changes in heart function are detected in the EKG, at which point the subject is directed to stop. Typical durations of such a test range from 10 to 20 minutes.
Conducting a maximal exercise test can require expensive equipment. People just beginning an exercise regimen are normally advised to perform this test only in the presence of medical staff due to risks associated with high heart rates. For general purposes, people instead typically use a formula to estimate their individual Maximum Heart Rate.
Formula for HRmax
Fox and Haskell formula; widely used.
Various formulas are used to estimate individual Maximum Heart Rates, based on age, but maximum heart rates vary significantly between individuals.[2] Even within a single elite sports team, such as Olympic rowers in their 20s, maximum heart rates can vary from 160 to 220.[2] This variation is as large as a 60 or 90 year age gap by the linear equations given below, and indicates the extreme variation about these average figures.
The most common formula encountered, with no indication of standard deviation, is:
HRmax = 220 − age
This is attributed to various sources, often "Fox and Haskell," and was devised in 1970 by Dr. William Haskell and Dr. Samuel Fox.[2] Inquiry into the history of this formula reveals that it was not developed from original research, but resulted from observation based on data from approximately 11 references consisting of published research or unpublished scientific compilations.[3] It gained widespread use through being used by Polar Electro in its heart rate monitors,[2] which Dr. Haskell has "laughed about",[2] as it "was never supposed to be an absolute guide to rule people's training."[2]
While the most common (and easy to remember and calculate), this particular formula is not considered by reputable health and fitness professionals to be a good predictor of HRmax. Despite the widespread publication of this formula, research spanning two decades reveals its large inherent error (Sxy=7-11 b/min). Consequently, the estimation calculated by HRmax=220-age has neither the accuracy nor the scientific merit for use in exercise physiology and related fields.[3]
A 2002 study[3] of 43 different formulae for HRmax (including the one above) concluded the following:
1) No "acceptable" formula currently existed, (they used the term "acceptable" to mean acceptable for both prediction of V_{\mathrm{O}_2 max}, and prescription of exercise training HR ranges)
2) The formula deemed least objectionable was:
HRmax = 205.8 − (0.685 × age)
This was found to have a standard deviation that, although large (6.4 bpm), was still considered to be acceptable for the use of prescribing exercise training HR ranges.
Other often cited formulae are:
HRmax = 206.3 − (0.711 × age)
(Often attributed to "Londeree and Moeschberger from the University of Missouri")
HRmax = 217 − (0.85 × age)
(Often attributed to "Miller et al. from Indiana University")
HRmax = 208 − (0.7 × age)
(Another "tweak" to the traditional formula is known as the Tanaka method. Based on a study of thousands of individuals, a new formula was devised which is believed to be more accurate
In 2007, researchers at the Oakland University analysed maximum heart rates of 132 individuals recorded yearly over 25 years, and produced a linear equation very similar to the Tanaka formula—HRmax = 206.9 − (0.67 × age)—and a nonlinear equation—HRmax = 191.5 − (0.007 × age2). The linear equation had a confidence interval of ±5-8 bpm and the nonlinear equation had a tighter range of ±2-5 bpm.
These figures are very much averages, and depend greatly on individual physiology and fitness. For example an endurance runner's rates will typically be lower due to the increased size of the heart required to support the exercise, while a sprinter's rates will be higher due to the improved response time and short duration, etc. may each have predicted heart rates of 180 (= 220-Age), but these two people could have actual Max HR 20 beats apart (e.g. 170-190).
Further, note that individuals of the same age, the same training, in the same sport, on the same team, can have actual Max HR 60 bpm apart (160 to 220): the range is extremely broad, and some say "The heart rate is probably the least important variable in comparing athletes."
The 2010 research conducted at Northwestern University revised maximum heart rate formula for women. According to Martha Gulati et al. it is:
HRmax = 206 − (0.88 × age)
