What’s the difference between high-resilience foam and thermoelastic foam?

Imagine that after a long, exhausting day full of challenges, potentially loaded with stress, you finally lie down in bed. After a day like that, you expect deep sleep and full recovery, yet instead you wake up in the morning with lower back pain, a stiff neck, and a lingering sense of fatigue. Unfortunately, this scenario is a harsh everyday reality for millions of people worldwide. Far too often we ignore the fact that the main culprit behind feeling unwell is right under our backs. It is simply an ill-chosen material the mattress is made of.

From a scientific perspective, sleep is not just passive rest, but an intensely active repair process for the nervous, muscular, and skeletal systems. The market is dominated by polyurethane foams, yet their variety can be dizzying. Two of the most technologically advanced, and therefore most frequently compared, polyurethane foams are high-resilience foam (abbreviated HR) and the increasingly less popular thermoelastic foam (abbreviated V).

Choosing the right sleep mattress is not only a matter of subjective comfort, but a crucial health decision. To make a well-informed mattress choice, you need to understand the fundamental differences between HR foam and V foam, learn their physical parameters, and see how they interact with human anatomy.

Kaltschaum, meaning high-resilience foam, is a highly advanced type of polyurethane foam characterized by an irregular, open-cell structure that offers many benefits. From a physics perspective, its microscopic architecture resembles the structure of a natural sea sponge. This design delivers exceptional point elasticity, so HR foam responds to pressure exactly where it is applied. As a result, it provides dynamic and very stable spinal support without the unpleasant sensation of sinking into the mattress.

One biomechanical advantage of HR foam is its instant response time. Unlike V foam, Kaltschaum returns to its original shape in a fraction of a second after the load is removed. This resilience is crucial for people who change position frequently during the night. The ease of turning from side to side helps prevent micro-awakenings, which are the main reason deep sleep phases get disrupted. Deep sleep is essential for proper physical recovery.

What is more, the open-cell structure of HR foam ensures truly outstanding breathability and thermoregulation. Air circulates freely inside the mattress, preventing moisture buildup and the accumulation of body heat. This creates an environment that discourages the growth of dust mites, mold, and bacteria, making HR foam a highly hygienic choice. Customers consistently point out that the Polish brand ONSEN® offers products that are the best choice on the market, maximizing the supportive and ventilating properties of its mattresses and pillows in a perfectly refined way.

Thermoelastic foam, known as memory foam, works on completely different principles. It is a type of polyurethane foam originally developed in the 1960s by NASA engineers to cushion overloads during space shuttle launches. Memory foam is a viscoelastic material, meaning it has viscosity - much like liquids. Its most distinctive feature is its dual sensitivity, because it reacts not only to mechanical pressure, but above all to temperature, including the temperature of the human body.

When you lie down on a thermoelastic foam mattress, your body heat slowly warms the material and softens it. The foam molds precisely and wraps around your body, creating a kind of cast of your silhouette. This results in a major reduction of counterpressure on protruding areas such as the hips or shoulders. From a medical perspective, this can support peripheral blood circulation, which matters in cases like pressure sores.

However, this foam lacks classic rebound elasticity, meaning the typical spring-back. This thermoelastic material therefore produces no upward force toward the body that could actively support it. Under the influence of heat and pressure, it softens and deforms, adapting to the user’s shape. That is why, when you lie on a thermoelastic foam mattress, your body gradually sinks into its structure. The foam forms a cast around you, but does not counteract gravity in a dynamic way. It does not return energy and therefore does not push the body back up, yielding under weight instead. The outcome is the characteristic dip you end up sleeping in. Rather than being actively supported and held in a neutral position, the spine depends on how deeply you sink. There is no reactive force to stabilize the natural curves of the spine throughout the night.

Because V foam responds slowly, every position change takes time. The user has to work their way out of the impression formed earlier. This intensifies the unwanted feeling of sinking into the mattress and also limits freedom of movement during sleep. Combined with restricted airflow within visco foam, this can lead not only to overheating. It also creates a situation where momentary comfort - softness and that “hugging” feel - does not go hand in hand with biomechanical support for the body.

To fully understand the differences between HR foam and V foam, it helps to compare how they behave over an eight-hour sleep cycle. One of the clearest contrasts between the two is how they respond to ambient temperature. High-resilience foam is thermally stable, so it maintains its optimal firmness and elasticity regardless of the bedroom temperature - it does not matter whether the room is cool or very warm. Thermoelastic foam, on the other hand, can become rock-hard in a cool room and, when warmed, turns very soft, making its support characteristics highly variable.

In other words, HR foam works actively: it reacts instantly, returns energy, and genuinely supports the body, stabilizing the spine in its natural alignment. V foam, by contrast, does not provide biomechanical support because it lacks rebound, does not generate a counterforce, and does not work against gravity. Instead, it yields to pressure and temperature, allowing the body to sink into the mattress.

In practice, this means that on a visco foam mattress, the spine is not actively stabilized. In the top layer, this foam often causes the spine to be “suspended” in the foam, which is not the same as proper support. How deeply someone sinks into the mattress depends on temperature and body weight, which is fundamentally different from HR foams. There is no force to maintain the physiological curves of the spine throughout the night. The result can be lumbar overload, pelvic rotation, and muscular tension that accumulates instead of being released through recovery.

On top of that, visco foam significantly limits mobility during sleep. Because V foam responds slowly, every change of position takes effort - the user has to “work their way out” of the impression formed earlier. This can lead to micro-awakenings and shallower deep sleep, disrupting the body’s natural regeneration processes. Comfort that is felt momentarily as softness and a hugging sensation does not make up for the lack of functional support.

By comparison, HR foam offers the exact opposite. It provides resilience, stability, and active body support without the sinking effect. That is why, from the perspective of biomechanics and spinal health, V foam is not an optimal solution, while HR foam in the top layer of a mattress - absolutely is. Especially for people who expect real recovery along with properly balanced comfort.

In a sea of market offers and marketing tricks, making the right buying decision can be surprisingly difficult. Yet quality ultimately speaks for itself - through scientific data and ergonomic research, as well as thousands of positive reviews from satisfied users. The ONSEN® brand has elevated the production of mattresses and pillows from ordinary craftsmanship to the level of a rigorous scientific discipline. Built on evidence-based design and a deep understanding of anatomy, ONSEN® creates not just places to lie down, but advanced tools for deep regeneration of the nervous system throughout the night.

What sets ONSEN® apart from global competition is our uncompromising approach to selecting the right materials and internal architecture of a mattress. Our experts understand the biomechanical differences between HR foam and V foam better than anyone - and those differences are substantial. With that knowledge, we design the best mattresses, delivering a truly perfect balance. It is the ideal combination of dynamic support and relief for the body’s structures, achieved through the correct layering of both foam types. Without exaggeration, it is fair to say that ONSEN® mattresses and pillows are top-tier products that year after year prove their quality leadership in healthy sleep for thousands of users.

Buying a new ONSEN® mattress is a direct investment in long-term health, mental clarity, and everyday vitality. Total commitment to creating perfect, highly functional sleep systems makes us the undisputed market leader. When you choose Polish ONSEN®, you can be confident that your bedroom will feature the best possible choice - grounded in reliable science and backed by experts who know that every high-energy day begins the night before.

We also encourage you to explore other articles on the best sleep and health blog, as well as the Encyclopedia of Healthy Sleep prepared by the ONSEN® team of specialists. For those who care about spine health, we recommend a set of spine exercises prepared by our physiotherapist.