News flash: Women's hearts are not men's hearts.

It isn't the first time a study for one sex has been wrongly generalized to cover both. This time it appears that the way to calculate peak heart rate, originally based on a study entirely of men, has been found to be wrong when applied to women. For men, the peak heart rate is 220 - age. That means a 40-year-old man should have a peak heart rate of 180 beats per minute. Women, however, should instead use the formula 206 - 88% of age, so a woman of the same age should have a peak heart rate of 171 beats per minute.

This changes a few very important things. One's peak heart rate is used to calculate the recommended healthy range of heart rates (65% to 85% of peak) to stay within while working out. Furthermore, using the new formula specific to women, researchers are now able to better predict a woman's risk of heart-related death.

Thanks to Barbara for the link.