July 23, 2008 The term “stress” was first used in a biological sense in the 1930s and as the world has increased in complexity and pace, is fast reaching epidemic proportions in most societies. Ironically, when biomedical scientists set out to develop new ways of studying stress, they needed an inconspicuous measuring tool so they could monitor the stress levels of their subjects during the course of their day-to-day environment. The idea of a “stress sensor vest” originated, and while they’re still studying stress, the vest has emerged as a viable and marketable product in its own right.

People’s muscle tension changes with their stress level – the greater the stress, the more likely the muscles are to produce a synchronous twitching effect. Though this is barely perceptible, the electrodes register the change.

The “stress sensor vest” registers the electrical excitation of the wearer’s muscles at any given time and determines the level of physical stress. The vest has sensors woven into the fabric that register the electrical excitation of the muscle fibers, and thin conducting metallic fibers then pass the signals to an electronic analysis system.

The idea of the sensor vest originated with biomedical scientists at the Catholic University of Leuven, Belgium, who needed an inconspicuous measuring tool for stress studies. Until then, they had affixed electrodes directly to their test subjects’ chests. But this itself induced stress, with the result that the tests delivered very little useful information. The new vest is designed to ensure a more relaxed test environment.

The project members are exploring further potential applications such as a special vest for computer games. By selectively tensing the torso muscles, players could use the vest to control figures on the monitor and for instance burst their heroes’ chains and fetters. The vest could also contribute to safety at the workplace – perhaps ensuring that workers do not lift loads that are too heavy for them. And sports coaches could tell from the electronic vest whether athletes have reached their performance limits or still possess energy reserves.

“The most important requirement for everyday use is a robust electronic system,” says Torsten Linz of the Fraunhofer Institute for Reliability and Microintegration IZM in Berlin, the partner responsible for the “packaging”. The entire electronic system has to be resistant to water and perspiration. The electric conductors must not fray even after repeated laundry cycles, and the sensors must be no larger than buttons to ensure that the garment is comfortable. The IZM researchers have meanwhile developed stable metallic fibers, watertight connections and durable sensor buttons.

Their task over the next few months will be to integrate the analysis electronics. The project partners have already demonstrated during field hockey training that the vest really works; it enabled players to choose the ideal moment for striking the ball and to hit it much further than usual.