What Is an Isotonic Foam Mattress?

An isotonic foam mattress is made of a special material that gently conforms to body contours for more comfortable sleeping. Isotonic foam may be utilized as part of a complete mattress unit or a separate pad for regular mattresses. This special material contains polyurethane foam combined with other chemicals to increase its density and viscosity. An isotonic foam mattress is pressure sensitive and slowly returns to its original shape when not in use. This mattress was originally used to relieve pain and prevent pressure sores for hospital patients.

An isotonic foam mattress is commonly referred to as a memory foam mattress. This mattress is designed to conform to individual body contours by offering lower resistance to pressure. Isotonic foam is not only utilized for complete mattresses, but can also be purchased as a separate top padding for a conventional coil-spring mattress. The density of the material can help relive pain in pressure points caused by ordinary bedding. Isotonic foam is usually much heavier and more expensive than traditional polyurethane foam.

This specialized mattress is constructed of polyurethane foam combined with certain other chemicals that increase its overall density and viscosity. Isotonic foam often has a slightly sticky feel when used without a fabric covering. The thickness of this material can have a significant effect upon a user’s comfort. Very thin layers of isotonic foam compress too easily and provide little or no cushioning effect. Extremely thick layers are usually too soft for a comfortable sleeping surface.

An isotonic foam mattress is available in both high and low density versions that have different reactions to weight and heat. Isotonic foam density can usually be determined by how quickly the material returns to its normal shape after pressure is applied and released. High-density foam reacts primarily to heat and molds to body contours slowly. A low density isotonic foam mattress is more sensitive to weight and quickly conforms to body contours. Low-density foam tends to have a somewhat shorter lifespan than high density material, but is often more comfortable to sleep on.

This material was originally developed for the U.S. space program in the 1960s. It began to be used commercially in the 1980s for certain hospital applications. Patients confined to a hospital bed for long periods of time experienced less pain and bedsores when lying on an isotonic foam mattress, for example. By the early 1990s, these mattresses began to be sold to the general public as an alternative to traditional coil-spring bedding. Their use has become very widespread in recent years as manufacturing costs have decreased.