Popular clinician and biomechanics expert Wendy Murdoch has a way with words…and body parts. In 40 5-MINUTE JUMPING FIXES, the second book in her bestselling 5-Minute Fixes Series, she talks booty happiness—that is, the “Smiley Butt” vs. “Frowny Butt” phenomenon.
“There is an anatomical limit as to how much space the rider’s seat can offer to the horse’s back,” says Murdoch. “I developed the terms ‘smiley butt’ and ‘frowny butt’ to illustrate two of these positions: the former when the femurs are in a neutral position, and the latter when they are in external rotation.”
The femur (the bone of the thigh) has a wide range of movement because of the hip joint’s ball and socket design. External rotation is when the ball rotates in the socket so the legs turn outward (and internal rotation the opposite—ie, pinching with the knees), but there is only one position where the femur distributes the rider’s weight over the greatest surface area along the horse’s back and around the rib cage—and that is neutral.
“For the most width across the seat, the greater trochanters [the tops of the femurs] must be the farthest distance away from each other,” explains Murdoch. “This occurs when the thighs are neutral between internal and external rotation. The pelvis (via the hip sockets) moves around the ball without restriction. When viewed from the back, the bone shape of the greater trochanters and seat bones across the seat of a skeleton looks to me like a smile.
“When the femurs are externally rotated (knees out) seat width is decreased at the back, reducing the amount of space for the horse’s back underneath the rider. This position also limits the movement of the pelvis. As the greater trochanters rotate back and come closer together, the bones look like a frown on the skeleton when viewed from the back.”
So remember the Booty Happy Test, riders. Because if your backside is smiling, you and your horse probably are, too.
Wendy Murdoch’s 40 5-MINUTE JUMPING FIXES is available at the TSB online bookstore, where shipping in the US is FREE.
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