Live Longer with the Right Amount of Exercise

A new tool may help predict the risk of death among women based on their exercise capacity, reports the New England Journal of Medicine (2005;353:468–75). By using this tool, women may measure whether their fitness level is adequate to protect them against fatal disease.

Exercise capacity is defined as the maximal amount of oxygen taken up by the body during an exercise test until exhaustion. Metabolic equivalents of exercise capacity can be estimated by performing an exercise stress test on a treadmill. Exercise capacity, a predictor of the risk of death and cardiac events such as heart attack and stroke, is influenced by various factors including gender, age, and state of health.

A graph was developed to estimate the percentage of the predicted exercise capacity for men of different ages. The man’s age in years is plotted along the left vertical axis and their metabolic equivalents along the right vertical axis, with a scale in between that defines exercise capacities in terms of percentages from 10 to 150%. A line is drawn connecting the person’s age to his metabolic equivalents; the point where this line intersects with the scale on the interior of the graph is the percentage of the predicted exercise capacity for that particular person. A value of 100% is average; values below this indicate that the person has a lower than average exercise capacity than do other people of the same age, and higher values indicate a better than average exercise capacity.

The goals of the new study were to establish a similar graph for women to help predict the risk of death from different causes. A total of 5,721 healthy women and 4,471 women with suspected cardiovascular disease took part in the trial. The population of healthy women was predominantly white; by contrast, almost one third of the women with symptoms of cardiovascular disease were black. Participants underwent an exercise stress test during which they walked on a treadmill until they became exhausted or could not continue due to other symptoms. The metabolic equivalents of the healthy women were used to create an exercise capacity graph, and the percentage of predicted exercise capacity was correlated with the survival rates of the participants.

Among the healthy women, those who had less than 85% of the predicted exercise capacity for their ages were more than 2 times as likely to die of any cause, and almost 2.5 times as likely to die from a cardiac event as were women with 85% or greater of their predicted exercise capacity. The results were similar for women with symptoms of cardiovascular disease. In general, the further below the normal values for exercise capacity, the higher the risk of death in both groups.

It appears that the graph constructed in this study may help estimate women’s risk of death based on individual exercise capacities. It is simple to use, requiring only a woman’s age and the metabolic equivalents derived from an exercise stress test. As getting the proper amount of exercise affects longevity, this tool will be useful for women interested in designing an exercise program for optimal health.

Kimberly Beauchamp, ND, earned her bachelor’s degree from the University of Rhode Island and her Doctorate of Naturopathic Medicine from Bastyr University in Kenmore, WA. She cofounded South County Naturopaths in Wakefield, RI. Dr. Beauchamp practices as a birth doula and lectures on topics including whole-foods nutrition, detoxification, and women’s health.

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