Teenagers and people in their twenties need five hours of exercise each week to avoid developing high blood pressure when they’re older. In a study published in the American Journal of Preventive Medicine, researchers at the University of California-San Francisco followed about 5,000 adults from 18 to 30 for three decades. They found that young adults need twice the amount of exercise than the federal guidelines currently recommend. High blood pressure, or hypertension, is often called the “silent killer.” It can lead to heart attacks, stroke, and even dementia. And the CDC says that nearly half of all adults in the U.S. have hypertension. So getting more exercise early in life is critically important later in life.