Date Published: February 22, 2019
Publisher: Public Library of Science
Author(s): Per-Øyvind Torvik, Erna Dianne von Heimburg, Torkel Sende, Boye Welde, Luca Paolo Ardigò.
The benefits of using longer than self-selected poles have been shown in double poling, but these potential benefits have not been examined in the gear 3 ski skating sub-technique (G3), during which the poling movement is very similar to double poling. The aim of this study was to examine the effect of longer than self-selected poles on physiological and perceptual responses in the G3 sub-technique. Ten cross-country skiers and biathletes (VO2max 72.4 ± 3.0 ml∙min-1∙kg-1, age 20.1 ± 2.8 years, height 1.81 ± 0.03 m and weight 73.1 ± 4.6 kg) completed two tests, each with three different submaximal intensities, during roller skiing using the G3 technique. The first test was carried out at a fixed speed (10 km∙h-1) and the skiers performed two intervals of 5 min at 7, 9 and 11% inclination on a roller ski treadmill with self-selected poles (SSP) and 7.5 cm longer poles (LP) at each step. The second test had a fixed inclination of 4% and speeds of 14, 17 and 20 km∙h-1, also performed with SSP and LP at each step. At fixed speed, the oxygen uptake was 2.7% lower (P = 0.005) and the gross efficiency (GE) 2.1% higher (P = 0.01) with LP than with SSP at the steepest inclination of 11%. At fixed inclination, the oxygen uptake was 2.1% lower (P = 0.01) and the GE was 4.1% higher (P = 0.03) with LP than with SSP at the highest speed of 20 km∙h-1. At 14 km∙h-1, the oxygen uptake was 3.0% lower (P = 0.05) and GE was 3.8% higher (P = 0.03) with LP than with SSP. Our novel findings show that longer poles in the G3 technique may enhance the efficiency of skiing.
Effectively utilising metabolic energy to produce high speed is a crucial factor for endurance performance in sports like cross-country (XC) skiing . The constant change in workload in XC skiing due to varying track conditions (changing snow and weather conditions) and track profiles consisting of different types of terrain (flat, uphill, downhill) challenge athletes with respect to the use of different sub-techniques and types of muscle use that require major adaptability of the cardiovascular system . The speed and technique on the uphills is of particular interest since ~50% of race time is spent there [2, 3], and the main time differences between skiers have been reported to occur during uphill skiing [4, 5].
The primary aim of this study was to investigate the effect of pole length on physiological and perceptual responses as a result of increasing speed and inclination for submaximal roller- skiing with the G3 ski skating sub-technique. The main findings in the current study were as follows: 1) LP induced lower VO2-uptake and higher GE in the two highest submaximal workloads, i.e. at 11% inclination and at 20 km∙h-1, compared to SSP. 2) At 4% inclination and at the lowest speed of 14 km∙h-1, the VO2-uptake was also lower and GE higher with LP compared to SSP. 3) The participants’ RPE on SSP and LP at all conditions were not significantly different. 4) The LP showed a greater knee angle at the two highest submaximal workloads compared to SSP conditions. 5) Additionally, there were no significant differences in cycle characteristics between SSP and LP at the two highest submaximal workloads.
The novel finding of this study is the superiority of longer poles over self-selected poles in G3 uphill ski skating sub-technique in terms of gross efficiency and VO2-cost both on uphill and at high speed on flatter terrain. Moreover, these results were associated with a more extended knee angle in the lowest position when using longer rather than self-selected poles. This latter finding may indicate that skiers have less vertical displacement when using longer poles, which can, at least partly, explain the lower VO2-cost and higher gross efficiency. While skier ratings of perceived exertion were not different between pole lengths at any of the submaximal workloads, clear differences of economy were observed. It is likely that cross-country skiers who choose longer poles rather than the typically preferred pole length have a modest metabolic advantage in G3 skating. Future studies should examine to what extent pole ground contact time and pole force effectiveness could explain the benefits of pole length in skating, and whether our findings would apply during outdoor on-snow skiing where air drag also plays a role.