Science and Nordic Skiing II 139 Effects of short- and long-term maximal and submaximal strength training on strength and endurance performance B. Welde 1 , Ø. Sandbakk 2 1 Department of Sport and Physical Education, Nord-Trøndelag University College, Levanger, Norway 2 Department of Human Movement Science, Norwegian University of Science and Techno- logy, Trondheim, Norway 1 Introduction The requirements of strength for endurance performance depend on the exercise mode employed and the competitive time. Since endurance training is the essential stimulus for endurance athletes, they do not prioritize high volumes of strength training (Sandbakk et al. 2011; Esteve-Lanao et al., 2005; Fiskerstrand and Seiler, 2004). However, recent research has demonstrated that short-term interventions of strength concurrent to endurance training can improve endurance performance considerably (Mikkola et al., 2007; Hoff et al., 2002; Hoff et al., 1999; Paavolainen et al., 1999; Johnston et al., 1997). Currently, there is a lack of long-term studies on the effects of strength training concurrent to endurance training. The well-known work of Hickson (1980) revealed for the first time that concurrent strength and endurance training may attenuate the increase in maximal strength. Several investigators have followed up this study, where a consistent finding is that strength gains are reduced when strength training is combined with high volumes of endurance training (six or more endurance training sessions per week) (Rønnestad et al., 2012). However, the effects of combined strength and endurance training on strength gains beyond 12 weeks in endurance athletes has not yet been performed. Load is regarded more important for the effects of maximal strength training than the number of repetitions (Campos et al., 2002). However, this aspect has not yet been examined in relation to the effects on endurance performance. For endurance athletes, with low initial levels of maximal strength, it remains to be examined whether maximal or submaximal strength