The research proposes a full body suit to detect muscle shape deformations. The suit consists of a stretchable sensor composed of a photo reflector (made up of a photo transistor and an infrared(IR) LED) and a spring. The photoreflector is embedded in the spring. When the spring is not stretched, the emitted IR light will reflect back to the phototransistor. However, when the spring is stretched, some of the emitted IR light can flow out through the aperture of the spring, reducing the light reflecting back to the transistor. Therefore, the more the spring is stretched, the less the amount of light would be detected. Here, a virtual reality(VR) system that can synchronize avatar bodies with users' muscle shape deformations.