Based on a systematic review of scientific studies dating back nearly 70 years, researchers at Johns Hopkins Medicine and collaborating institutions suggest that ambulation—walking or exercising without assistance—is not sufficient alone as a preventive measure against venous thromboembolism (VTE), a potentially deadly condition in which a blood clot forms, often in the deep veins of the leg, groin or arm (known as a deep vein thrombosis) and may dislodge. If that happens, the clot will travel via the bloodstream to lodge in the lungs and cause tissue damage or death from reduced oxygen (known as a pulmonary embolism).