Construction of an Ergonomic Mattress Firmness Classification System and Its Impact on Sleep Health

1. Mattress Firmness Classification System and Biomechanical Characteristics

Internationally, a 1–10 numerical scale is widely adopted to quantify mattress firmness, with higher values indicating greater firmness. Significant differences exist across firmness levels in terms of tactile feel, spinal biomechanical response, and pressure redistribution capabilities (see Table 1).

Table 1: Comparison of Biomechanical Characteristics of Mattresses by Firmness Level

Note: Levels 7–8 represent the medically recommended "medium-firm" range. Levels 9–10 lack necessary micro-elasticity, which can lead to lumbar suspension, and are only advised for specific pathological needs. For the general population, Levels 7–8 are preferable.

2. Physiological Effects and Target Demographics of Different Firmness Levels

2.1 High-Support Mattresses (7–8)

Physiological Effects:​ This firmness range effectively limits excessive spinal flexion, aligning with the German IGR (Campaign for Healthier Backs) ergonomic certification standards. It offers physical therapeutic benefits for patients with lumbar disc herniation and ankylosing spondylitis. Additionally, high support reduces abdominal compression, which can alleviate gastroesophageal reflux symptoms. Material-wise, firm mattresses with coir or 3D fiber cores typically exhibit air permeability ≥1200 mm/s (based on P.U.Lab data), significantly outperforming traditional foam materials and mitigating heat and moisture buildup in the sleep microenvironment.

Target Demographics:

1. Individuals with Higher Body Weight (BMI >28 or weight >80 kg):​Require robust support to prevent spring system sagging; reinforced structures with spring wire diameters ≥2.2 mm are recommended.
2. Individuals with Spinal Conditions or Supine Sleepers:​7-zone individually pocketed spring systems are recommended; clinical data indicate they can limit lumbar suspension to ≤5%, providing targeted support.
3. Adolescents During Developmental Stages:​Require maintenance of natural spinal curvature during sleep; Level 7 (medium-firm) is the primary recommendation.

Material Caution:​ Traditional pure coir mattresses should be avoided due to excessive firmness and susceptibility to moisture and mite infestation. Opt for thermally bonded coir or 3D fiber materials certified under OEKO-TEX® Standard 100 (Baby Class) to ensure chemical safety and avoid formaldehyde emissions from adhesive bonding.

2.2 Balanced Mattresses (4–6, Primary Recommendation)

Physiological Effects:​ Medium-firm mattresses achieve an optimal biomechanical balance between "support" and "conformability." For adults weighing 50–80 kg, this firmness maintains sagittal spinal balance, significantly reducing morning back pain caused by inadequate support. Structurally, individually pocketed spring systems offer excellent motion isolation (measured motion noise ≤23 dB, reducing partner disturbance by 80%). When combined with solvent-free eco-friendly manufacturing and GB 31701-2015 Class A infant-grade fabrics, they ensure durability, environmental safety, and skin-friendliness.

Target Demographics:

1. Sedentary Office Workers:​Empirical studies show 88.5% of participants reported reduced morning back fatigue after use.
2. Combination Sleepers and Pregnant Individuals:​Require accommodation for shoulder/hip sink-in during side sleeping alongside lumbar support during back sleeping.
3. Sensitive Skin and Infant/Maternal Groups:​Households with stringent requirements for material safety.

Fit Test Standard:​ When side sleeping, the spine should remain horizontally aligned with hip sink-in depth <3 cm. When back sleeping, one to two fingers should fit snugly between the waist and mattress without noticeable gaps.

2.3 Pressure-Relieving Mattresses (1–3)

Physiological Effects:​ These mattresses utilize highly viscoelastic materials (e.g., memory foam) to achieve full-body contouring, minimizing shear forces between skin and fabric and alleviating pressure concentration on bony prominences.

Target Demographics:

1. Low-Body-Weight Individuals (<50 kg):​Prevents discomfort from pressure points on overly firm surfaces.
2. Specific Pathological Needs:​Individuals with arthritis or those in post-operative recovery requiring reduced friction during movement.
3. Specific Scenarios:​Space-saving solutions for studio apartments or lofts, and younger renters preferring a "cloud-like" sleep experience. 

Contraindications:​ Long-term use by individuals >90 kg may lead to structural sagging. Not recommended for those with lumbar conditions or developing adolescents due to risks of spinal deformity or chronic strain.

The scientific selection of mattress firmness fundamentally involves balancing spinal biomechanical support with uniform body pressure distribution. The established 1–10 firmness classification system clarifies the differential impacts of each level on spinal alignment, pressure redistribution, and ease of movement.