The elements of passive suspension.
Platform Glide v Skid.
Snowboards and skis can glide, skid, pivot, and drift. All are useful handling options. That said, skis and snowboards are most effective as a base for athletic movement when they glide on their long axis. The gliding action allows the working edge to slide/slice rather than scrape, and allows the materials used in manufacture to ‘do their thing’.
Platform Flex and Surface Amplitude.
Skis and snowboards are built to flex along their length. The amount/rate of overall flex is indicative of how much energy that ski might store and return, but also of what kind of terrain variation the ski itself can ‘absorb’, or follow while gliding. In other words, if the ski has a total mid body deflection of 8cm, that gliding ski can ‘pass through’ a terrain variation 8cm in height without much difficulty. That said, stiffer and softer skis will each react differently to that 8cm variation, in terms of ‘spring back’. To this end, a slalom ski will be stiffer in flex, a GS ski will be softer, and a DH ski will be softer still.
Skis and snowboards are produced with a variety of materials, and the composition will vary depending on end use. Wood or foam cores, carbon fiber, fiberglas, rubber, plastic and metal in the layup, and invariably steel edges. Each material, and how it is assembled in relation to the other materials, will determine how the platform will or will not vibrate/resonate as it moves over/through the snow. Regardless of ingredients, the gliding ski will adhere closer to an ‘ideal’ frequency as per construction than will the skidding ski.
Vibration moving through the length of the platform is damped/absorbed better than vibration introduced from the side, as vibration traveling the long axis passes through more material/mass than it does on the short axis. A ski or snowboard with glass construction, if used well, will be ‘more stable’ than a ski or snowboard of metal construction skied poorly.
Muscle Mass as Damper
Adding weight to the platform is one of the easier ways to smooth the ride. There was an era when blocks of aluminum rubber and plastic were attached to the ski tip and tail. The current trend involves additional metal laminates and polyethylene top sheets. The extra mass itself is harder to vibrate, while the resonant characteristics of that mass play a related part. Together, they offset the rate at which dissonance at the ground level can propagate to the athlete. To a point, this strategy works, but too much weight can adversely affect handling, which may then alter/erode technique. Added weight can put more stress on the body, possibly leading to injury.
A more effective approach will somehow isolate the upper body mass from ground level disturbance; and thus isolate body mass disturbance from affecting ground level performance. When properly isolated, the athlete’s torso/upper body can serve as a form of ‘tuned-mass’ damper; a means of stabilizing the interaction between surface and platform.
Tall buildings have to manage wind load. Left unchecked, wind induced sway can lead to structural failure, so it’s best to limit or damp the motion to prevent destructive harmonics. Elastic/flexible materials can be incorporated between the various internal and external structural members. When the wind pushes the exterior of the structure, some of that energy is ‘lost’ in the flexible coupling before it can affect the inner structure. Similarly, if wind gusts push hard enough to affect the inner members, energy can be similarly dissipated during the ‘spring back’ from that push.
The tuned coupling essentially provides a time delay between onset of load and reaction of material. This time delay prevents all of the structure from moving as one unit, thereby preventing/disrupting resonance.
The following video provides an explanation of the TMD as used in the F1 Renault R25. The principles discussed are directly applicable to skiing and snowboarding. This mechanism was so effective, it was banned from competition the following year.
Muscle Tension: Bracing v Constant ‘push’
Dedicated athletes are consistently working to improve their game. Trying ‘harder’ can be equated with greater physical effort, in part because increased effort can be realized, in the felt sense, in real time. If that greater effort creates parasitic muscle tension*, tension that rigidly binds one limb segment to another without appreciable athletic gain, an athlete may inadvertently create a rougher ride .
To the contrary, slack muscle tissue can serve as an effective isolation medium.
In the following video, notice how the repeated impact of the left ski tip starting @ 00:27 is dissipated by slack muscle tissue.
High level athletes generally take the greater loads of a turn on straighter limb segments, whereas recreational athletes often take those loads on more flexed limb segments. The leg extension itself does not imply the posture is locked, stiff, or otherwise rigid. The ‘taller’ stance might seem more unstable, but it is not, at least not at the level of advanced skill development.
A lowered stance can feel safer and more stable on both skis and snowboard. This, on account of the center of mass being closer to the snow, and that arrangement feeling less tippy than when the center is higher. In a lowered stance, however, body weight and the variable loads associated with direction change are supported on muscle, more so than on bone. Enduring muscular support is tiring, and limits movement options. At the same time, this puts the athlete into what could be called a ‘bracing’ relationship with the platform, where the center of mass is essentially ‘held’ a particular distance above the platform for the duration of the turn.
Bracing will also firmly couple the greater body mass to the working edge of the platform, and that inflexible mass can exert disruptive inputs on the working edge. This in turn reduces stability, as the platform is receiving erratic control inputs. That lack of stability contributes to fatigue, and that fatigue impairs free and supple movement in a degenerative spiral.
To counter the bracing tendency, aim to avoid engaging both the quadriceps group and the biceps femoris at the same time. These are the opposing muscles at the front and back of the thigh.
If an athlete can maintain/modulate their relationship to their platform primarily with quadriceps extension, by way of exerting a progressive, continuous ‘push’ against the resistance of the arcing platform, the rider’s upper body mass can be better isolated from the base of support.
In the following video, between 2:25 and 2:37, notice how disturbance at the ground level does not travel to the core.
The principle of a muscle group working without opposition can also be observed in the context of pedaling a hard-tail mountain bike over rough terrain. It’s astounding how fast one can ride without adding significant load to the cardiovascular system when peripheral muscle tension has been resolved. While there can be a number of contributing factors, origin and resolution of tension is usually related to cleat position and saddle setback. In skiing and snowboarding, extraneous muscle tension is often directly related to boot/binding geometry.
Tuning these variables can be extremely frustrating, so there’s more enthusiasm for finding ways to avoid the task entirely.
In off-road cycling, the market has used full-suspension frames as a means of smoothing the ride for the greater number of recreational riders. In skiing and hard boot snowboarding, various mechanisms have been employed between the rider and platform as a means of cushioning the ride. Both of these approaches have value, but their effect is magnified when the common sources of muscle tension present in each activity are addressed.
For the most part, cycling, skiing, and snowboarding are simply recreation. As such, there is a practical division between time spent practicing/fixing/tuning, and time spent doing. The doing of the thing rightfully takes priority over diagnostics and deconstruction, and the market is ready to supply easy solutions that might keep an enthusiast from having to dive deep into the bio-mechanical weeds.
In concept, the passive suspension concept is straightforward. It’s simply the manner in which a platform interacts with the surface, the construction of the platform, and the prevalent physicality of the athlete. Making full use of the existing passive suspension system will reduce the effort required to stabilize travel over the snow. This provides greater capacity to ride how and where you want to.
*Ideally, the ski/snowboard platform will enhance stability on a slippery surface. Parasitic tension exists when the moving platform instead generates instability. In the absence of dependable stability underfoot, muscle tension is used to stabilize the system. Typically, this involves locking limb segments for periods of time. These periods may be brief or sustained, and often cyclical. When an athlete adopts an over-flexed, braced posture, there is tension in the system, but as this is often a choice, it’s not wholly parasitic in nature. Both of these scenarios, however, place an enormous drag on the cardiovascular system, meanwhile compromising performance.
Next: Suspension System/Active