Researchers have developed a nomogram (alignment chart) specifically for women that can be used to predict their expected exercise capacity at any given age, as well as demonstrated that the resulting measure is a predictor of the risk of death.
Women whose exercise capacity was less than 85 percent the age-predicted value had twice the risk of death compared to women reaching at least 85 percent. according to research led by Martha Gulati, MD, a cardiologist at the Bluhm Cardiovascular Institute of Northwestern Memorial Hospital, which will be published in the August 4 issue of the New England Journal of Medicine.
"This is the first study of its kind in women," said Dr. Gulati. "Despite extensive research on the role of exercise stress testing and exercise capacity, there has been a lack of data on what is normal or expected for healthy women. Until now, they have been evaluated using the men's nomogram, which does not provide an accurate assessment for women."
Exercise capacity can be estimated by performing a symptom-limited stress test based on the speed and grade of the treadmill. It is defined as the maximal oxygen uptake for a given workload and can be expressed in metabolic equivalents (MET). MET is the amount of oxygen used by an average seated person and increases with the intensity of exercise.
To utilize the nomogram to establish the percentage of predicted exercise capacity for age requires only the woman's age and exercise capacity achieved in MET on the exercise stress test. Drawing a straight line between the age and exercise capacity will allow the determination of the percentage of predicted exercise capacity for age; a value of 100 percent is the mean for any given age. Any result greater than 100 percent indicates better-than-average performance. Any result lower than 100 percent indicates some degree of functional impairment for age.