Upper-Body Muscular Endurance Training Improves Performance Following 50 min of Double Poling in Well-Trained Cross-Country Skiers

Abstract

This 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, VO_2max running: 64 ± 5 mL·kg^-1·min^-1) were counter-balanced to either a combined muscular endurance and running interval training group [MET; n = 11 (♂ = 9, ♀ = 2)], or an endurance running interval training group [ET; n = 11 (♂ = 9, ♀ = 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 × 30 repetitions, 90 s rest between sets) and running intervals (3 × 4 or 2 × 6 min, 3 min rest), while ET performed running intervals only (6 × 4 or 4 × 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 VO_2max 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 VO_2max running or VO_2peak 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.

Keywords: O2-cost; cross-country skiing; high-intensity training; maximal oxygen uptake; running; training intensity.

Figure 1

The standing double poling exercise used during testing and training. The figure illustrate the poling phase of the cycle. The participant gave his consent to publish the picture.

Figure 2

Schematic illustration of prolonged double poling protocol. Steady-state VO₂ was measured from 5 to 20, 31 to 35, and 46 to 50 min followed by a self-paced 1,000-m maximal test. ↓ = start O₂ measurements. ↑ = end O₂measurements. All tests conducted at 2.5° incline and the speed shown is the average from both groups. Speed from 0 to 5 min was identical to 5 to 10 min.

Figure 3

Muscular endurance (A) and 1RM (B) in the standing double poling exercise before (pre) and after (post) 6 weeks of combined endurance- and muscular endurance training (MET) or endurance training (ET). Data are expressed as group mean ± standard deviation. ^*Significant change from pre- to post-test (P < 0.05). ^**Significant differences from pre- to post-test between MET and ET (P < 0.05).

Figure 4

1,000-m time before (pre) and after (post) 6 weeks of combined endurance training and muscular endurance training (MET) and endurance training (ET). Data are expressed as group mean ± standard deviation. ^*Tendency to change from pre- to post-test (P = 0.06).

Figure 5

Relative change in speed during the 1,000-m time trial from pre- (black horizontal line at 0%) to post-test. Data are expressed as group mean ± standard deviation. The speed was set the first 200 m. All tests conducted at 2.5° incline. ^*Significant differences from pre- to post-test between combined endurance training and muscular endurance training (MET) and endurance training (ET) (P < 0.05).

Figure 6

O2-cost; VO₂ (A,B), respiratory exchange ratio, RER (C,D) and heart rate, HR (E,F) during the prolonged 50-min double poling protocol before (pre-test) and after (post-test) the 6-week intervention period. MET, Combined endurance training and muscular endurance training (left), ET, endurance training (right). Data are expressed as group mean ± standard deviation. ^*Different from pre-test (P < 0.05).

Figure 7

Percent individual changes from pre- to post-test: (A) 1,000-m time, (B) muscular endurance, (C) VO_2peak double poling (mL·kg⁻¹·min⁻¹) and (D) average O₂-cost from the following measuring intervals: 8 to 10, 13 to 15, 18 to 20, 33 to 35, and 48 to 50 min. MET, Combined endurance training and muscular endurance training (gray columns); ET, endurance training (black columns).