Optimized Custom-Made Ski Sledges (image) Fraunhofer-Gesellschaft Caption Professional athlete and wheelchair user Martin Fleig trains with a ski sledge. Credit Ruben Elstner, MikroTribologie Centrum µTC Usage Restrictions The picture may be used for editorial purposes only. It is protected by copyright. The use is free of charge if the reference is mentioned. Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.