Force production, balance control and muscle activation in different sitting positions - pilot study for disabled sit sledge cross-country skiers - Rapp, W.; Lindinger, S. J.; Lappi, T.; Ohtonen, O.; Linnamo, V. (Abstract Book of the 6th International Congress on Science and Skiing, December 14 - 19, 2013 St. Christoph am Arlberg - Austria, 2013)