The technique has been tested on turkeys in the hope of finding a benefit that could be used for astronauts. Engineering issues came into play when they tried to upgrade the test machine to support the weight of a human being. Once the vibration intensity grew strong enough to lift over 40 kg, fractures appeared in the steel. The first bed-rest study using a vibration training device for humans was done by the European Space Agency (ESA) in 2003 in Berlin (Berlin Bedrest Study, BBR). The same technology was then used in several parabolic flight campaigns of the DLR (German Aerospace Agency) starting in 2006 where the feasibility of use of a lightweight vibration training device under microgravity conditions was demonstrated and ein 2009 and 2010 where basic research on influence of microgravity on vibration training effects was investigated.