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The World is Not Smooth and Flat
Historically, wheelchairs have been designed primarily for rolling on flat and smooth surfaces. On such a surface, Static Stability is all that is required. A Statically Stable wheelchair stays upright at all times. For example, many wheelchair basketball and tennis wheelchairs have an additional wheel in the rear which prevents it from flipping over backwards. Highly cambered rear wheels enhance ease of turning (spinning) and increase lateral stability. Players are strapped tightly to their wheelchairs to make sure that they stay in them at all times. The basketball and tennis courts are ideal surfaces for wheelchairs and Static Stability is widely utilized.
On the other end of the athletic spectrum are hospitals. Hospital wheelchairs are heavy, wide and stable. Hospitals and athletic courts are perfect surfaces for wheelchairs and as a result, their respective wheelchairs are designed to maximize Static Stability. Unfortunately for wheelchair users, the real world is not smooth and flat. There are inclines, declines, bumps, curbs, steps, cracks, side hills, and soft terrain to deal with. Navigating these surfaces is more easily accomplished by deploying some degree of Dynamic Stability. The Static Stability that works so well in ideal settings now becomes a hindrance on uneven terrain.
A Dynamically Stable wheelchair is one that is able to be easily controlled on the rear two wheels as needed, as opposed to requiring all four wheels on the ground at all times. This configuration makes navigating uneven/rough terrain easier and many times safer too.
Creating Dynamic Stability requires the user to actively control his wheelchair with his movements. The user’s actions are the driving component of the user/wheelchair system. Static Stability on the other hand is independent of the user. In fact, the user could be a sack of potatoes and the wheelchair would still be stable.
Many in the manual wheelchair community don’t seem to understand that wheelchairs should be thought of in the same manner that adaptive skiers view sitskis. Skiers don’t think of themselves as potatoes to be hauled around. They recognize the importance of their movements coupled with acquired skill leading to greater levels of mobility and independence.
Manual wheelchair users will require differing levels of Static Stability on an individual and situational basis. But it is ultimately Dynamic Stability that creates high level wheelchair performance on the rough terrain of the real world. Therefore, wheelchairs need to be optimized with the goal of enabling as much Dynamic Stability as possible given the requirements and constraints of each individual’s Static Stability needs.
The Dark Age of Wheelchair Knowledge
In comparison to adaptive skiing, wheelchair community is in the Dark Age of Knowledge. Most “experts” from the medical, manufacturer, and sales fields only view wheelchairs in terms of Static Stability. Many high-performing wheelchair users, intuitively shun Static Stability for Dynamic Stability, but most are unable to logically articulate their reasons. In addition, many of them feel that all wheelchair users should do just as they do. They don’t take into account that a higher level of disability will require a higher level of wheelchair Static Stability in order to increase his or her individual level of dynamic performance.
Society doesn’t view the wheelchair as a tool for enabling high-level mobility performance. It is viewed as a necessary evil for providing low level functional mobility. Many people feel that any level of ambulation regardless of how slow, awkward, or limited is more desirable than using a wheelchair. As a result, society puts little thought and effort into improving each wheelchair user’s mobility performance.
On the other hand, adaptive skiing is all about improving individual performance regardless of disability. Adaptive skiers understand and capitalize on the relationship between Static Stability and dynamic skiing performance. A wheelchair on rough, uneven terrain is subject the same laws of physics as a sitski on the snow. Just as the optimum amount of Static Stability maximizes skiing ability, so does the optimum amount of Static Stability maximize wheelchair mobility.
The manual wheelchair community is in the Dark Ages because it doesn't understand and take advantage of this relationship. Influenced by society’s belief that wheelchairs are medical devices that primary provide for the user’s safety and postural support, much of the manual wheelchair community doesn’t recognize that wheelchairs are devices that enable real world mobility in the same way that sitskis are mobility devices for the snow.