Although there is a theoretical basis for crossing legs to increase blood pressure, there are no published data addressing this question. As a result guidelines for measurement of blood pressure are not consistent in recommending that patients' legs should not be crossed during measurement.
To determine the effect of crossing legs on blood pressure.
Fifty healthy volunteers and 53 patients with hypertension were randomly allocated in a study with a crossover design to having seated blood pressure measured with their legs in three different positions: feet flat on the floor and legs crossed using two common methods. The blood pressures were assessed by an investigator who was blinded to the leg positions and used a fully automated sphygmomanometer.
Crossing legs during blood pressure measurement increased systolic (by average 8.1 mmHg, 95% confidence interval 5.1–11.1 mmHg for method 1; 10.5 mmHg, 6.5–14.6 mmHg for method 2) and diastolic (by 4.5 mmHg, 1.5–7.5 mmHg for method 1; 4.0 mmHg, 2.0–6.0 mmHg for method 2) blood pressures in patients who have hypertension. Crossing legs increased systolic blood pressure (by 2.5 mmHg, 1.3–3.8 mmHg for method 1; 2.3 mmHg, 0.9–3.7 mmHg for method 2) in the healthy volunteers but had little effect on diastolic blood pressure. The cardiovascular-risk class increased for a large number of the hypertensive patients but for fewer of the normotensive subjects.
Blood pressure increases when legs are crossed and this increases the estimation of cardiovascular risk for many patients. Care should be taken to ensure that the patients' feet are flat on the floor when measuring their blood pressure.