The Science Behind Compression Set

Compression set is one of the most overlooked problems in wheelchair seating.

At first glance, foam cushions appear supportive and stable. But inside the material, something very different is happening over time.

Compression set refers to the permanent deformation that remains after foam has been compressed under load. In simpler terms, the foam loses its ability to fully rebound.

Every time a wheelchair user sits, the foam compresses beneath the pelvis, thighs, and bony prominences. Over days, weeks, and months, the foam cells begin to fatigue.

Eventually, the cushion no longer returns to its original shape.

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This creates several major concerns: (1)

• Reduced pressure redistribution

• Increased bottoming out

• Loss of pelvic stability

• Increased shear forces

• Uneven posture support

• Increased skin breakdown risk

The process accelerates under heavy loads, prolonged sitting, heat, and moisture.

What makes compression set especially dangerous is that it often happens gradually. The client may not immediately notice the loss of support until discomfort, leaning, redness, or skin breakdown begins. 

AIREZ 2.0 approaches this problem differently.

Instead of foam, AIREZ uses a flexible elastomer lattice engineered for repeated deformation and rebound. The material flexes with movement but returns to its original geometry without permanent collapse.

This allows the cushion to maintain support consistency far longer than traditional foam systems.

For clinicians, that means the seating system fitted on day one behaves more predictably over time. And in custom seating, predictability matters.

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(1) (International Pressure Injury Guideline — Seating, 2025)

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Ana Endsjo, MOT/R, CLT

Director of Clinical Education and Marketing

Ana Endsjo is the Director of Clinical Education & Marketing at Matrix Seating USA and a contributing faculty member at University of St. Augustine for Health Sciences. With over 20 years of experience in occupational therapy, seating and mobility, and clinical education, she specializes in custom seating, assistive technology, and clinician training. Ana is passionate about advancing client outcomes through education, innovation, and practical clinical solutions within the complex rehabilitation technology industry.