The wearable concept „muscle shirt“ measures the level of athletic performance by detecting the heartbeat with a sensor integrated into the fabric. If physical activity is measured the fabric contracts. It is gathered on the back of the shirt. By contraction the wearable physically transforms. The transformation ranges between the properties “wide” and “comfortably tight”. It is perceived by the skin surface and has the potential to enhance the adequate posture of the wearer. The transformation can also be associated with psychological values like speed and agility, which are directly related to physical activity during exercise. The transitions of the transformation are fluent and do not include any fixed steps, nor imply any categories. In contrast to existing self-tracking apps, this reproduction of physical activity corresponds with the human body perception and delivers adequate space for innate intuition. In addition to the haptic experience the registered measurements are also communicated in a visual way. The upper layer of the fabric has a finely sliced structure that gets pulled apart through the contraction and reveals an underlying colored layer. The originally monotonous seeming grey fabric transforms into a colorful and lively appearing piece of fashion and second skin.
For prototyping the effect was realized with a stepper motor. The motor is connected to the heartbeat sensor and rotates a bar which gathers the fabric at the back of the shirt if athletic performance is measured. In the future, to make ist more "wearable", the effect could be realized with shape memory wires, which are integrated into the fabric. The wires have the ability to contract and relax by minimal, imperceptible electrical power impulses.