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WILLIAMSBURG, VA. -- Researchers at Duke University Medical Center have found that the more physically fit a woman is, independent of regular exercise, the lower her blood pressure level is during a stressful day at work.

The findings are significant because high blood pressure at work is associated with a greater risk of heart disease than high blood pressure in the clinic or in a physician's office, according to Elizabeth C. D. Gullette, a behavioral medicine researcher and project coordinator of the study.

"Our findings suggest that for working women, physical fitness may buffer against the work-related stress that causes blood pressure to rise," Gullette said. The subjects in the study were mildly hypertensive working women, aged 31 to 57, who were moderately overweight and who had not exercised regularly for at least six months.

Results of the study, funded by a five-year grant from the National Heart, Lung and Blood Institute, were prepared for presentation at the annual meeting of the American Psychosomatic Society.

In the study, 24 women were given exercise treadmill tests to determine their precise levels of fitness. The women also wore portable blood pressure monitors at home and at work for a 15-hour period to assess changes in blood pressure during routine activities.

Women who were more physically fit, as determined by greater oxygen consumption during the exercise test, had lower blood pressure levels at work than women who were less physically fit. The physically fit women also had smaller blood pressure changes between home and work environments than unfit women. Researchers said the rise in blood pressure at work suggests that unfit women react more strongly and negatively to work pressures than physically fit women.

High blood pressure at work is dangerous because studies have shown it to be more predictive of left ventricular hypertrophy (LVH), or enlargement of the heart's left ventricle, than home blood pressure or blood pressure measured in the clinic.

LVH is a major risk factor for coronary artery disease and may be a more significant predictor than cigarette smoking or high cholesterol levels, according to numerous studies, including one published in the May 1995 issue of the Journal of the American Medical Association.

The researchers now are conducting a longitudinal study of women enrolled in an exercise program to determine whether exercise training can further reduce blood pressure levels at work.