A new chart can tell women of any age how much exercise they need to stay fit.

"This is the first study of its kind in women," said Dr. Martha Gulati, a cardiologist at Northwestern Memorial Hospital.

"Despite extensive research on the role of exercise ... there has been a lack of data on what is normal or expected for healthy women," she said.

Age-based fitness standards for men don't apply to women. (AP file photo)
Age-based fitness standards for men don't apply to women. (AP file photo)

Until now, women have been evaluated using men's charts. The results caused many false positives, meaning women thought they were at higher risk for premature death than they really are, Gulati explained in a release.

The chart shows what level of exercise a women needs to reach maximum fitness at all ages.

To develop the chart, Gulati and her colleagues compared 5,721 women with no symptoms of heart disease to 4,471 women who were suspected of having heart disease.

Both groups were given treadmill stress tests to measure their fitness levels. The researchers then tracked how many of the women, matching mortality rates with exercise capacity.

On the chart, a score of greater than 100 per cent indicates a better-than-average performance for your age, while less points to an impairment.

The fitness levels are based on metabolic equivalents or METs that reflect the intensity of physical activity.

Workout guide

For example, a 60-year-old woman who reaches seven METs on a treadmill would score 100 per cent for her age.

A 30-year-old achieving the same seven METs would reach only 65 per cent of the fitness level predicted for her age.

Normal, healthy women who were not able to achieve 85 per cent of the predicted level were twice as likely to die prematurely than those who met or exceeded the goal, the researchers found.

The chart could help women to tailor their workouts to achieve the best exercise capacity for their age.

The study appears in Thursday's issue of The New England Journal of Medicine.

In a commentary accompanying the study, Drs. William Kraus and Pamela Douglas of Duke University Medical Center in Durham, N.C. point out the study's authors did not provide a statistical comparison of the normal values for men and women to clarify its importance, or justify why they used an 85 per cent cutoff point.

Nonetheless, Kraus and Douglas said the findings are important, and doctors should use the information to help their male and female patients, given that stress tests are easy and inexpensive.