How much exercise is enough for women? Are women getting enough out of their cardiovascular exercise?  These are a few questions that are finally being researched and answered so that women can be smarter and more efficient in their workouts. Cardiovascular fitness, or exercise capacity, is an established predictor of cardiac health. There has been an historical lack of data for women. Until now, the only guidelines available were for men and as determined by current research is not applicable to women. This research has shown that exercise capacity for a woman at any given age is slightly less than a man and cardiac fitness declines at approximately 1%  per year.  Declines in cardiovascular health decline more rapidly for women than men. Research has now determined how much exercise a woman should be able do for her age.

In a report that compares the cardio capacities of thousands of women, both symptomatic and asymptomatic for cardiac complaints, researchers have been able to determine how much exercise is enough for any given age to get the greatest cardiovascular benefit.  This research appears in August 4^th, 2005, New England Journal of Medicine.  Over a period of ten years in the Chicago area from data obtained as part of the community-based St. James Women Take Heart Project, Dr. Martha Gulati, lead author, was able to predict what effect the right dosage of exercise would have on cardiac health.  An age-predicted exercise capacity was established for asymptomatic women.  Now instead of following the guidelines established for men, women can rely on a chart or nomogram to determine how hard they should exercise for the most benefit at their age.

The clinical significance of Gulati et al is greatly enhanced by the ease with which fitness can be measured.  All women participating in this study underwent an exercise treadmill test and the researchers measured the level of fitness in units of METS or metabolic equivalents.  METS indicate how hard you are working or how much the oxygen the body is consuming.  One MET is 3.5 milliliters of oxygen per kilogram of body weight per minute.  As the activity becomes more physically challenging the number of METS increase.  For example, just sitting quietly for a minute is 1 MET.  Moderate walking is about 3 – 6 METs, carrying golf clubs is approximately 5 METs.  The beauty in using METs as a parameter is that most cardio-equipment in a gym setting or in home use has a MET setting – most people using the equipment do not know what the information means.

By following the women who participated in the study, Gulati et al, were able to predict what effect the right amount of exercise would have.  Age- predicted exercise capacity was established by averaging the results of the stress tests in asymptomatic women.  The study found that women who scored less than 85 percent of their age-predicted exercise had double the risk of dying of any cause, and more that two-and-a-half times the risk of dying of cardiac disease.  By using the METs and age chart, determining how hard we need to work will be made easier for women. So what does this mean for the average women exerciser?  We have a nomogram or a chart; see Figure 1, which helps us see how hard we are working according to our age.  For a woman of 60, 7 METs is 100 percent of predicted exercise capacity.  But for a woman of 30, it is only 62 percent of capacity – not enough to lower her risk for cardiac illness.

There are a few limitations to the study as indicated by the authors, but it is a step in the right direction for women’s health. This study allows women to monitor how much harder they need to do their cardio-vascular portion of their workout.  It provides new values for women’s exercise capacity and cardio-respiratory fitness and documents a strong relationship between these variables. The amount of time spent exercising is still very important but by reaching the maximum METs for your age, even for a short duration, you know you are getting the most out of your workout.  Knowing that your heart can sustain that pace is great feedback and is positive reinforcement in our quest for improving our cardiovascular health.  Bottom line:  As women we need to increase our cardiovascular fitness – to get the maximum benefit while we exercise.  As always, before beginning and exercise program or boosting to the next level, please be sure to consult your health care provider or someone who is familiar with this study and can make the appropriate recommendations.

In general, as women, we need to be smarter about our workouts to get the maximum benefits in all areas, not only cardiovascular – but in injury prevention, increasing our strength and increasing our endurance to do all the things we love to do.

Sources:
Gulati M, Black HR, Shaw LJ, et al.  The prognostic value of a nomogram for exercise capacity in women. N Eng J Med 2005;353:468-475.

Kraus, WE, Douglas PS. Where does fitness fit in?  N Eng J Med 2005;353:517-519.

- Donna Schneider, BS, CES, CPT, CEAS