This is a video of U.S. military guys leading some Iraquis in physical training. Watch as they attempt jumping jacks. It is scary. Remember, this is a skill you mastered by the 2nd grade.
I conclude the following are potential reasons for what you see in this video:
1. A Stolichnaya Vodka shipment fell off a ship and floated down the Pacific towards the Indian Ocean where it was picked up and consumed by these solidiers on empty stomachs.
2. They read this article entitled: How to Do Jumping Jacks.
3. They just watched this guy and were weak-kneed
4. Insert random reasoning based on the other side of the world myths (sun rises in the west, water drains in the opposite direction, crop circles, midgets smell like cabbage, etc.)
Jumping Jacks are tough.