If they were merely a stack of bones, the 33 vertebrae of the spine would be as vulnerable as the tower of building blocks in a game of Jenga. Te connective tissues and muscles that attach to and surround these bones make the spine a sturdy support for the entire body. For the spine to serve, literally and figuratively, as the “backbone” of effective movements, a skier should employ the strength of the core muscles in the torso. Te spine needs to remain stacked in its most biomechanically effective posture to resist strong forces.
Te spine’s flexibility, a great asset in many circumstances, also means there are many ways to flex or twist the spine into a weaker position. Tat’s why a
FIGURE 4.1: Regions and components of the spine. CERVICAL
THORACIC
LUMBAR
SACRAL COCCYX
functionally strong core is critical to skiing. It is only when a skier’s core muscles support the vertebrae that the core will be stable enough for the limbs to effectively move in opposition to the spine.
JOINTS
A joint is the juncture where two bones meet. Some joints can only move in one plane of motion, while others can move in all three. Te range of motion of a joint is the distance it is capable of moving along the direction of its plane(s) of motion. A hinge joint flexes and extends in a single plane. For example, the elbow is a hinge joint. Te knee is a modified hinge joint; it also glides and permits a minimal amount of rotation. Like a joystick, a ball-and-socket
joint has the ability to move in all three planes, giving it a broad range of motion. Te shoulder and hip are examples of ball-and-socket joints. With a gliding joint, the bones glide (slide) along their smooth surfaces in a limited amount of movement, with components of roll as well as glide. Joints in the wrist and foot are gliding joints.
FIGURE 4.2: The elbow is an example of a hinge joint.
FIGURE 4.3: The shoulder joint is an example of a ball-and-socket joint
TheSnowPros.org
CHAPTER 4: BIOMECHANICS OF SKIING 61
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