Force production, balance controll, and muscle activation in different sitting positions - Pilot study for disabled sit sledge cross-country skiers - Rapp, W.; Lappi, T.; Lindinger, S.; Ohtonen, O.; Linnamo, V. (Science and Skiing VI. 6th International Congress on Science and Skiing, Dec. 14 - 19, 2013, St. Christoph am Arlberg, 2015)