Anterior Posterior Seat Position
Little is known about the optimum anterior-posterior position of the wheelchair seat, although this position affects both the chair's stability and the effectiveness of application of force to the handrim.
If the athlete is too far toward the rear of the wheel chair, there is a tendency for the chair to become unstable (particularly when going uphill) and for the athlete to "flip" out the back.
A rear seat position also makes it difficult for the athlete to apply force to the front of the handrim where the most effective application of driving force can be made.
If, on the other hand, the seat is too far forward the wheelchair (particularly if it is a three-wheeler) becomes less stable during downhill turns, and a greater percentage of the athlete's weight is carried by the front wheel(s), which increases the rolling resistance of the chair. Optimum positioning is usually achieved by trial and error.