Wheelchair Seat Depth

Too short - not enough support. Too deep - potential long term problems. Get the depth right.

It is critical to get the depth of the seat pan right when you specify the dimensions of your wheelchair. The seat pan should be deep enough so that the seat is in contact with as much of the bottom of your thighs as possible.

When the seat pan is too shallow, your upper legs extend beyond the front edge and more pressure is placed on your ischial "sitting" bones. This additional pressure increases the risk of skin breakdown. You are also giving up greater stability. The chair can't "carry" you if it can't make full contact with your body. Without full seat support, your body might be prevented from being in its neutral position, risking spinal curvature or muscle and tendon strain.

Picture a wheelchair...

A too shallow seat pan also means that your feet will not rest properly in the footrests. Picture a wheelchair with footrests designed to allow the lower legs to be perpendicular to the ground. If the knees extend out beyond the front of the seat, the legs will have to bend back at the knees so that the feet can rest on the footplates. In order for the feet to be level, they would have to bend unnaturally.

On the other hand, when the seat pan is too deep, you will be unable to sit properly against the chair back. You will be kept from sliding back fully in the seat, stopped behind the knees. When the seat is too deep, the only way to make contact with the back of the chair is to rotate the pelvis backwards and round the spine. In other words, you will have to slump. Slumping is potentially dangerous for the spine as it can cause degeneration. This posture also makes it difficult for you to wheel efficiently in a manual wheelchair.

A seat pan that is too deep could interfere with the position of your legs if you use calf supports with your footrests. Calf supports keep the legs in a more forward position. The seat pan might need to be shallower to compensate.

A deeper seat means you’ve chosen a longer frame, and so this means a heavier wheelchair due to the added metal in the frame. When more of the chair is ahead of the axle, you will feel as though you are pushing even more weight. If you require extra depth in the seat pan, you will need to adjust the forward position of the main wheel axles so that the wheelchair is not too front heavy, particularly if you rely on doing wheelies in your wheeling style.

I am very tall, and recently purchased a wheelchair that is two inches deeper than my past wheels so I could have more contact with my legs along the seat. It has worked very well, and it was not a problem to adjust the wheelchair for wheelies and for ease of wheeling, although it did feel slightly heavier at first. Now I can't tell the difference, partly because I have nothing to compare to anymore, and I probably gained a little strength to compensate for the additional weight just by using the chair.>

A crucial element that must be taken into consideration before you can determine the appropriate depth of the seat pan is the type of seat back you will use. A fabric upholstered back requires you to sit a little farther back in the wheelchair, and tends to loosen with time unless it is equipped with adjustable tension straps. A rigid back will not change much over time, but some are quite deep and cause you to sit more forward on the seat.