How CAPS II Supports Balanced Sitting and Postural Development
How CAPS II Supports Balanced Sitting and Postural Development
Postural seating plays a critical role in the health, comfort and functional ability of wheelchair users. For individuals with complex postural needs, achieving a stable and balanced sitting position is not simply about comfort. It affects breathing, digestion, communication, arm function and the ability to engage with the world around them.
The CAPS II seating system was developed to support these outcomes through a clinically informed modular seating approach. CAPS II aims to support alignment, guide posture and allow functional movement. Understanding the philosophy behind CAPS II helps explain why it continues to be widely used in wheelchair postural seating for both children and adults.
Why sitting posture matters
Sitting posture influences far more than how someone appears when seated. The position of the pelvis and trunk affects many essential bodily functions. When posture is poorly supported, individuals may experience:
- restricted breathing and reduced lung capacity
- difficulty swallowing or feeding
- reduced head control and visual engagement
- limited arm and hand function
- discomfort and fatigue during sitting
Over time, unsupported posture can become progressively fixed. As asymmetries develop, the body adapts to these positions, which can make later correction much more difficult. Effective wheelchair postural seating therefore aims to guide the body towards a balanced sitting posture. The pelvis is stabilised, the trunk is supported and alignment is encouraged so the user can maintain a symmetrical sitting position as comfortably as possible.
The CAPS II seating system was designed with this goal in mind: helping wheelchair users achieve stable, balanced sitting while still allowing movement and functional activity.
The clinical thinking behind CAPS II
The CAPS II seating system has its roots in clinical research conducted at the Chailey Heritage Foundation, which explored how postural management could support children and adults with complex disabilities. This research highlighted an important principle. Postural seating should not simply contain the body. Instead, it should support the development of functional sitting ability.
CAPS II reflects this philosophy through a simple progression: Support → Stability → Movement → Function
First, the seating system provides the support required to stabilise the pelvis and trunk. Once stability is achieved, the individual can maintain a more balanced sitting position. This stability allows the user to move more effectively, which in turn supports functional activities such as reaching, interacting and communicating. In other words, the seating system creates the conditions that allow the user to make the most of their abilities.
How CAPS II supports pelvic and trunk alignment
At the centre of any effective seating system is the pelvis. When the pelvis is stable and positioned correctly, the rest of the body is better able to align. CAPS II supports this alignment through a combination of adjustable components that work together to guide posture.
Pelvic support
A neutral pelvic orientation with respect to obliquity is supported on flat surface. A ramp is provided to account for the conical shape of the thighs, thus maintaining the hips at 90 degrees. Lateral pelvic guides stabilise the pelvis in mid-line.
Sacral support
Sacral support helps maintain the pelvis in a stable, neutral position with respect to pelvic tilt by supporting the posterior iliac superior spines (PSIS). By stabilising the base of the spine, it reduces the likelihood of posterior pelvic tilt and encourages a more neutral pelvic position.
Knee block
The knee block projects a posterior force through the femurs and hip joints, which are below the level of the PSISs, to hold the pelvis is neutral tilt. It applies only a small force through the knees; its primary purpose is not to prevent sliding.
Back support
Located above the sacral support, the back cushion is set back slightly to allow for the natural kyphosis of the spine, which avoids the person’s shoulders and head being pushed forward.
Thoracic laterals
Thoracic laterals provide adjustable support to the trunk. These supports help guide the upper body towards a symmetrical position and reduce lateral leaning, particularly for users with reduced trunk control.
Head support
Head supports help maintain head alignment and support users who may have limited head control. Correct head positioning is essential for communication, visual engagement and safe swallowing.
Arm support
A tray is provided to support the weight of the arms, thus reducing the loading on the spine from the shoulder girdle, and preventing the weight of the arms from dragging the shoulders forward, which would have an impact on head positioning. It also provides a surface on which functional activities can be performed.
Together, these elements help maintain pelvic stability and trunk symmetry, creating the foundation for balanced sitting.
Encouraging movement, not restricting it
One of the defining features of the CAPS II seating system is that it supports posture without unnecessarily restricting movement. Rigid seating solutions can sometimes limit the natural movement that users need to maintain comfort and function. CAPS II takes a different approach.
By stabilising the pelvis and guiding trunk alignment, the system creates a stable base from which movement can occur. This allows users to maintain upper body control and engage with their environment. Balanced sitting posture supports:
- improved head movement and visual orientation
- better arm and hand function
- increased interaction with surroundings
- greater tolerance for sitting over longer periods
Rather than holding the user in place, CAPS II aims to support movement within a controlled and aligned posture.
A system designed to evolve
Posture is rarely static. As individuals grow, develop or experience changes in their condition, their seating requirements can change as well. The modular design of the CAPS II seating system allows it to adapt over time. Adjustability within the system includes:
seat depth, seat width, and backrest height adjustments to accommodate growth
repositionable trunk supports
interchangeable components for evolving postural needs
This modular approach means the seating system can be modified as requirements change, reducing the need for frequent full replacements. For children in particular, this flexibility is valuable. As they grow and their physical needs develop, the seating system can be adjusted to maintain appropriate support and alignment.
Supporting posture for the long term
Achieving and maintaining balanced sitting posture is central to effective wheelchair seating. The CAPS II seating system was developed to support this goal through a clinically informed, modular approach that focuses on stability, movement and functional ability. By stabilising the pelvis, supporting trunk alignment and allowing controlled movement, CAPS II helps create the conditions needed for comfortable and functional sitting.
CAPS II is therefore more than a seating product. It is a clinically driven system designed to support posture, movement and long-term postural development for wheelchair users.
