xThis study investigated the effect of muscular endurance training on O2-cost and performance in double poling (DP) on a rollerski treadmill. Twenty-two well-trained cross-country skiers (31 +/- 4 years, 77 +/- 9 kg, 181 +/- 8 cm, VO2max running: 64 +/- 5mL/kg.1/min.1) were counter-balanced to either a combined muscular endurance and running interval training group [MET; n = 11 (m = 9, f = 2)], or an endurance running interval training group [ET; n = 11 (m = 9, f = 2)]. Both groups continued their normal low-and moderate intensity training, but replaced 2 weekly high intensity-training sessions with two project-specific sessions for 6 weeks. In these sessions, MET combined upper-body muscular endurance training (4 x 30 repetitions, 90 s rest between sets) and running intervals (3 x 4 or 2 x 6 min, 3 min rest), while ET performed running intervals only (6 x 4 or 4 x 6 min, 3 min rest). The DP test-protocol consisted of 50 min submaximal poling for O2-cost measurement, followed by a self-paced 1,000-m performance test. In addition, subjects performed a VO2max test in running. MET increased muscular endurance (P < 0.05) and 1RM in simulated DP (P < 0.01) more than ET. Further, MET reduced the 1,000-m time and O2-cost compared to baseline values (P < 0.05), and tended to improve the 1,000-m time more than ET (P = 0.06). There were no changes in VO2max running or VO2peak DP in either MET or ET. In conclusion, 6 weeks of muscular endurance training increased both muscular endurance and 1RM in simulated DP. Further, specific upper-body muscular endurance training improved DP performance and thus, seems as a promising training model to optimize performance in well-trained cross-country skiers.
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