The Washington Post – Ariana Eunjung Cha 
The adolescent years are when people’s bodies are supposed to start the ascent to their physical peak. Teenagers are growing like beanstalks. Their hormones are raging. They’re eager for new experiences. By all accounts, this should be among the most active periods in a person’s lifetime. Except it turns out it’s not. In an eye-opening study involving 12,529 Americans ages 6 to 85, researchers mapped how physical activity changes over a lifetime. The participants, part of the 2003-2004 and 2005-2006 cycles of the National Health and Nutrition Examination Survey, wore accelerometers, devices that measure movement, for seven consecutive days. For the purposes of the analysis, researchers counted all types of movement, not just exercise.(more)