Made of ‘electro-thermal isolation yarn,’ the concept device absorbs the heat generated by the body during exercise. A coil and magnet electricity generator stores the heat, and then releases it into the pad after the workout–creating a soothing warmth. The Knee Pad’s energy storing feature can be switched off or on, and the built-in rechargeable lithium battery will store the energy generated by the coil to produce heat at a later time.