Te pressure exerted against the scale is reduced, which can be seen in the reduction of the reading on the dial. Extension of the knees and hips pushes down on the scale, resulting in a momentarily higher reading until shortly after the extension movement is finished. Snowboarders must time these movements that decrease pressure in order to help redirect the board into a new turn.
CENTER OF MASS
So far, the rider has just been referred to as a body. As an instructor, you want to better understand balance so you will need more description. Center of mass (CM) is the conventional term, although sometimes “center of gravity” is used, and in most cases they can be thought of as interchangeable. CM is a slightly more accurate term for snowsports, as snowboarding involves elevation change and the pull of gravity changes slightly with elevation.
Te CM is the point at which the body’s mass is evenly distributed. Tink of a perfectly balanced teeter-totter, the CM (on one plane) is located at the fulcrum. Tat would be the “center” of its mass. If you were to balance the body along each of its cardinal planes (Chapter 4), the CM would be the confluence of those three planes.
Why be so technical, especially since the CM is not a set point, at least in a body that can move? Te reason for being so specific is that the CM is a dynamic concept that greatly impacts a rider’s ability to balance. Consider that in a rider raising his or her hands above head level, the CM location rises. Wearing a helmet also raises it. Conversely, the weight of the board, boots, and bindings lowers a rider’s CM. Making angles with the body can even take the CM outside of the body.
BALANCE Balance refers to the CM being located over the base of support (BOS). Moving the CM in one direction or another places the rider out of balance. Fore/aft imbalance is a common issue while riding. Tis is usually seen when the rider has more weight on the tail rather than distributing it equally over both feet.
Tis reaction is normal because the snowboard is sliding forward, and if Newton were watching he would explain it as action/reaction phenomena: snowboard forward, rider backwards. Tis is exactly what happens in the cartoons when an unsuspecting character steps on a banana peel. Peel goes forward, person goes backwards.
FIGURE 1.3: Center of mass moves throughout a turn.
PATH OF RIDER’S CENTER OF MASS
PATH OF SNOWBOARD
26 AASI SNOWBOARD TECHNICAL MANUAL
TheSnowPros.org
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