It's also not uncommon for a guy to violate that max HR rule, either. One website I read said that if you've exercised regularly, your max goes down 1 beat every 2 years instead of 1 every year for each year older than 30. I remember that because it conveniently works out for me.
Just remember, it is not a
rule. It is a gross guideline, only.
A very interesting article on the 220-age "myth."
http://faculty.css.edu/tboone2/asep/Robergs2.pdf
Here is an excerpt.
Based on this review of research and application of HRmax prediction, the following recommendations can be
made;
1. Currently, there is no acceptable method to estimate HRmax.
2. If HRmax needs to be estimated, then population specific formulae should be used. However, the most
accurate general equation is that of Inbar (17) (Table 3); HRmax=205.8-0.685(age). Nevertheless, the error
(Sxy=6.4 b/min) is still unacceptably large.
3. An acceptable prediction error for HRmax for application to estimation of VO2max is <±3 b/min. Thus, for
a person with a HRmax of 200 b/min, error equals ±1.5%. If this precision is not possible, then there is no
justification for using methods of VO2max estimation that rely on HRmax prediction formulae.
Prediction of Maximal Heart Rate
8
4. Additional research needs to be performed that develops multivariate regression equations that improve the
accuracy of HRmax prediction for specific populations, and modes of exercise.
5. The use of HRmax is most prevalent in the fitness industry, and the people who work in these facilities
mainly have a terminal undergraduate degree in exercise science or related fields. These students/graduates
need to be better educated in statistics to recognize and understand the concept of prediction error, and the
practical consequences of relying on an equation with a large standard error of estimate (Sxy).