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Breaking Falls

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This month it is my job to cover orthopedic injuries at the San Francisco General Hospital. Some of the stories are extraordinary and interesting like the bullet lodged in a femur that required a 3 hour operation for extraction or a police chase where the suspect jumped two adjacent buildings and subsequently fell 30 feet to break several bones. Instead of focusing on these I will describe something more mundane but much more likely to happen to us: a simple fall from a standing position. It is worth mentioning because it happens often, it leads to fractures and disability, and most people can improve on their falls.

My first reaction when I lose my balance and head toward the ground is to extend my arms and stop the ground from hitting me. In emergency medicine we call this a FOOSH—fall on out stretched hand. According to Newton’s second law of motion the acceleration of gravity multiplied by my mass generates a force that is transmitted entirely through the area of my hand, to my wrist, which includes the metacarpal bones, and through my radius and ulna—the bones in my forearm. Because all the force is transmitted through a small area and a rigid arm, it stresses the bone beyond its tensile strength and leads to a fracture.

The experts in falling—sky divers and paratroopers—have developed a technique to minimize injury during falls called the parachute landing fall (PLF). The principle behind the PLF is to distribute the force over a greater area by creating more points of contact between the ground and the body than an out stretched hand. Also by staying less rigid and thereby reducing the force directed through any given bone, the tensile strength is less likely to be exceeded. And by translating some of the force into angular momentum through a roll, even more force can be dissipated.

After seeing so many people splinted this month for fractures, I suggest--instead of stopping the ground from hitting you by extending out your arms--tyring to slow down your fall and sharing the blow with other parts of your body besides just the palm of your hand (but maybe not including the head). To do this I would let my lower leg contact the ground first, followed by my thigh, and my torso while covering my head with my arms. With over 5 points of contact the force would be more evenly distributed and by rolling afterwards each point would feel less force.

Have any of you skydivers reading this changed their falling mechanics, and what was your experience? I just tried it and it wasn't so bad.
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About the Author

The Stanford Emergency Room is the center of emergency care at Stanford University.

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