Laboratory tests are commonly performed by cross-country (XC) skiers due to the challenges of obtaining reliable performance indicators on snow. However, only a few studies have reported reliability data for ski-specific test protocols. Therefore, this study examined the test-retest reliability of ski-specific aerobic, sprint, and neuromuscular performance tests.; Thirty-nine highly trained XC skiers (26 men and 13 women, age: 22 ± 4 years, V̇O; 2max; : 70.1 ± 4.5 and 58.8 ± 4.4 mL·kg; -1; ·min; -1; , respectively) performed two test trials within 6 days of a diagonal V̇O; 2max; test, n = 27; skating graded exercise test to assess the second lactate threshold (LT; 2; ), n = 27; 24-min double poling time trial (24-min DP, n = 25), double poling sprint test (Sprint; DP1; , n = 27), and 1-min self-paced skating sprint test (Sprint; 1-min; , n = 26) using roller skis on a treadmill, and an upper-body strength test (UB-ST, n = 27) to assess peak power (P; peak; ) with light, medium, and heavy loads. For each test, the coefficient of variation (CV), intraclass correlation coefficient (ICC), and minimal detectable change (MDC) were calculated.; V̇O; 2max; demonstrated good-to-excellent reliability (CV = 1.4%; ICC = 0.99; MDC = 112 mL·min; -1; ), whereas moderate-to-excellent reliability was found for LT; 2; (CV = 3.1%; ICC = 0.95). Performance during 24-min DP, Sprint; DP1; , and Sprint; 1-min; showed good-to-excellent reliability (CV = 1.0%-2.3%; ICC = 0.96-0.99). Absolute reliability for UB-ST P; peak; was poor (CV = 4.9%-7.8%), while relative reliability was excellent (ICC = 0.93-0.97) across the loads.; In highly trained XC skiers, sport-specific aerobic and sprint performance tests demonstrated high test-retest reliability, while neuromuscular performance for the upper body was less reliable. Using the presented protocols, practitioners can assess within- and between-season changes in relevant performance indicators.
When exercising in the cold, optimizing thermoregulation is essential to maintain performance. However, no study has investigated thermal parameters with wearable-based measurements in a field setting among elite Nordic skiers. Therefore, this study aimed to assess the thermal response and sensation measured at different body parts during exercise in a cold environment in biathletes.; Thirteen Swiss national team biathletes (6 females, 7 males) performed two skiing bouts in the skating technique on two consecutive days (ambient temperature: -3.74 ± 2.32 °C) at 78 ± 4% of maximal heart rate. Heat flux (HF), core (T; core; ) and skin (T; skin; ) temperature were measured with sensors placed on the thigh, back, anterior and lateral thorax. Thermal sensation (TS) was assessed three times for different body parts: in protective winter clothing, in a race suit before (PRE) and after exercise (POST).; HF demonstrated differences (; p; < 0.001) between sensor locations, with the thigh showing the highest heat loss (344 ± 37 kJ/m; 2; ), followed by the back (269 ± 6 kJ/m; 2; ), the lateral thorax (220 ± 47 kJ/m; 2; ), and the anterior thorax (192 ± 37 kJ/m; 2; ). T; core; increased (; p; < 0.001). T; skin; decreased for all body parts (; p; < 0.001). Thigh T; skin; decreased more than for other body parts (; p; < 0.001). From PRE to POST, TS of the hands decreased (; p; < 0.01).; Biathletes skiing in a race suit at moderate intensity experience significant heat loss and a large drop in T; skin; , particularly at the quadriceps muscle. To support the optimal functioning of working muscles, body-part dependent differences in the thermal response should be considered for clothing strategy and for race suit design.
INTRODUCTION: The cross-country ski sprint prologue involves a 2 – 4 minute long effort on varying terrain with only the top 30 skiers advancing to the subsequent heats. Qualification success not only depends on physiological and technical capacity, but also on optimal pacing strategy and appropriate relative efforts in the various terrains (Sandbakk et al., 2011). METHODS: During the U23 Cross-Country Ski World Championships 2018 freestyle sprint prologue in Ulrichen (SUI), skiing performance in flat, uphill and downhill terrain was analyzed for female (N = 43) and male (N = 64) skiers using time-synchronized video recordings. Relative performance indices for the three different terrains were calculated (Vterrain / Vaverage). A Spearman’s rank order correlation for the terrain indices ranking and overall prologue ranking was calculated and potential sex differences regarding performance in the various terrains were analyzed by ANOVA. Table 1. Spearman’s rank correlation coefficients for terrain index rank and overall prologue performance and corresponding level of statistical significance. Overall prologue rank Women Men Flat index rank -0.42** -0.24 Uphill index rank 0.59*** 0.57*** Downhill index rank -0.39* -0.50*** *p < .05; **p < .01; ***p < .001 RESULTS: Terrain index rank correlations are shown in Table 1. Male skiers demonstrated higher uphill indices than females 0.62 ± 0.01 vs. 0.57 ± 0.02 (p < .001), with no significant differences found for flat and downhill terrain indices (both p > .05). DISCUSSION: A higher relative skiing effort for uphill terrain appeared to be correlated to overall rank in the investigated cross-country ski sprint prologue for both female and male skiers. At the same time, relative skiing performance in flat and downhill sections were negatively correlated to overall rank in the prologue, indicating a smaller relative effort and/or significance. Furthermore, male skiers demonstrated higher relative skiing velocities in the uphill track sections compared to female skiers, which was not observed regarding relative flat and downhill terrain efforts. CONCLUSION: The current study identified higher relative velocities invested during uphill terrain in faster skiers compared to slower skiers at an international freestyle sprint skiing competition, supporting the importance of performance indicators for uphill terrain. In addition, the difference in the relative effort investment between female and male skiers appeared to be only present in uphill terrain, indicating a sex differences in performance concerning uphill relevant performance factors and/or pacing strategy. REFERENCES Sandbakk, O., Ettema, G., Leirdal, S., Jakobsen, V., Holmberg, HC. (2011) Analysis of a sprint ski race and associated laboratory determinants of world-class performance. European Journal of Applied Physiology 111:947-957.
PURPOSE: To examine the effects of exercise-induced trunk fatigue on double poling performance, physiological responses and trunk strength in cross-country skiers. METHODS: Sixteen well-trained male cross-country skiers completed two identical pre- and post-performance tests, separated by either a 25-min trunk fatiguing exercise sequence or rest period in a randomized, controlled cross-over design. Performance tests consisted of a maximal trunk flexion and extension test, followed by a 3-min double poling (DP) test on a ski ergometer. RESULTS: Peak torque during isometric trunk flexion (- 66%, p < .001) and extension (- 7.4%, p = .03) decreased in the fatigue relative to the control condition. Mean external power output during DP decreased by 14% (p < .001) and could be attributed both to reduced work per cycle (- 9%, p = .019) and a reduced cycle rate (- 6%, p = .06). Coinciding physiological changes in peak oxygen uptake (- 6%, p < .001) and peak ventilation (- 7%, p < .001) could be observed. Skiers chose a more even-pacing strategy when fatigued, with the performance difference between fatigue and control condition being most prominent during the first 2 min of the post-test. CONCLUSIONS: In well-trained cross-country skiers, exercise-induced trunk fatigue led to a substantial decrease in DP performance, caused by both decreased work per cycle and cycle rate and accompanied by reduced aerobic power. Hence, improved fatigue resistance of the trunk may therefore be of importance for high-intensity DP in cross-country skiing.
