Mid Sweden University

The purpose was to examine skiing velocities, gear choice (G2-7) and cycle rates during a skating sprint time trial (STT) and their relationships to performance, as well as to examine relationships between aerobic power, body composition and maximal skiing velocity versus STT performance. Nine male elite cross-country skiers performed three tests on snow: (1) Maximum velocity test (Vmax) performed using G3 skating, (2) Vmax test performed using double poling (DP) technique and (3) a STT over 1,425 m. Additional measurements of VO2max during roller skiing and body composition using iDXA were made. Differential global navigation satellite system data were used for position and velocity and synchronized with video during STT. The STT encompassed a large velocity range (2.9-12.9 m s-1) and multiple transitions (21-34) between skiing gears. Skiing velocity in the uphill sections was related to gear selection between G2 and G3. STT performance was most strongly correlated to uphill time (r = 0.92, P < 0.05), the percentage use of G2 (r = -0.72, P < 0.05), and DP Vmax (r = -0.71, P < 0.05). The velocity decrease in the uphills from lap 1 to lap 2 was correlated with VO2max (r = -0.78, P < 0.05). Vmax in DP and G3 were related to percent of racing time using G3. In conclusion, the sprint skiing performance was mainly related to uphill performance, greater use of the G3 technique, and higher DP and G3 maximum velocities. Additionally, VO2max was related to the ability to maintain racing velocity in the uphills and lean body mass was related to starting velocity and DP maximal speed.

Cycle and force characteristics were examined in 11 elite male cross-country skiers using the diagonal stride technique while skiing uphill (7.5 degrees) on snow at moderate (3.5 +/- 0.3m/s), high (4.5 +/- 0.4m/s), and maximal (5.6 +/- 0.6m/s) velocities. Video analysis (50Hz) was combined with plantar (leg) force (100Hz), pole force (1,500Hz), and photocell measurements. Both cycle rate and cycle length increased from moderate to high velocity, while cycle rate increased and cycle length decreased at maximal compared to high velocity. The kick time decreased 26% from moderate to maximal velocity, reaching 0.14s at maximal. The relative kick and gliding times were only altered at maximal velocity, where these were longer and shorter, respectively. The rate of force development increased with higher velocity. At maximal velocity, sprint-specialists were 14% faster than distance-specialists due to greater cycle rate, peak leg force, and rate of leg force development. In conclusion, large peak leg forces were applied rapidly across all velocities and the shorter relative gliding and longer relative kick phases at maximal velocity allow maintenance of kick duration for force generation. These results emphasise the importance of rapid leg force generation in diagonal skiing.

This investigation was designed to analyse the kinematics and kinetics of cross-country skiing at different velocities with the herringbone technique on a steep incline. Eleven elite male cross-country skiers performed this technique at maximal, high, and moderate velocities on a snow-covered 15° incline. They positioned their skis laterally (25 to 30°) with a slight inside tilt and planted their poles laterally (8 to 12°) with most leg thrust force exerted on the inside forefoot. Although 77% of the total propulsive force was generated by the legs, the ratio between propulsive and total force was approximately fourfold higher for the poles. The cycle rate increased with velocity (1.20 to 1.60 Hz), whereas the cycle length increased from moderate up to high velocity, but then remained the same at maximal velocity (2.0 to 2.3 m). In conclusion, with the herringbone technique, the skis were angled laterally without gliding, with the forces distributed mainly on the inside forefoot to enable grip for propulsion. The skiers utilized high cycle rates with major propulsion by the legs, highlighting the importance of high peak and rapid generation of leg forces.

To improve current understanding of energy contributions and determinants of sprint-skiing performance, 11 well-trained male cross-country skiers were tested in the laboratory for VO2max , submaximal gross efficiency (GE), maximal roller skiing velocity, and sprint time-trial (STT) performance. The STT was repeated four times on a 1300-m simulated sprint course including three flat (1°) double poling (DP) sections interspersed with two uphill (7°) diagonal stride (DS) sections. Treadmill velocity and VO2 were monitored continuously during the four STTs and data were averaged. Supramaximal GE during the STT was predicted from the submaximal relationships for GE against velocity and incline, allowing computation of metabolic rate and O2 deficit. The skiers completed the STT in 232 ± 10 s (distributed as 55 ± 3% DP and 45 ± 3% DS) with a mean power output of 324 ± 26 W. The anaerobic energy contribution was 18 ± 5%, with an accumulated O2 deficit of 45 ± 13 mL/kg. Block-wise multiple regression revealed that VO2 , O2 deficit, and GE explained 30%, 15%, and 53% of the variance in STT time, respectively (all P < 0.05). This novel GE-based method of estimating the O2 deficit in simulated sprint-skiing has demonstrated an anaerobic energy contribution of 18%, with GE being the strongest predictor of performance.

PURPOSE: To examine the metabolic responses and pacing strategies during the performance of successive sprint time trials (STTs) in cross-country skiing. METHODS: Ten well-trained male cross-country skiers performed four self-paced 1300-m STTs on a treadmill, each separated by 45 min of recovery. The simulated STT course was divided into three flat (1°) sections (S1, S3 and S5) involving the double poling sub-technique interspersed with two uphill (7°) sections (S2 and S4) involving the diagonal stride sub-technique. Treadmill velocity and V˙O2 were monitored continuously and gross efficiency was used to estimate the anaerobic energy supply. RESULTS: The individual trial-to-trial variability in STT performance time was 1.3%, where variations in O2 deficit and V˙O2 explained 69% (P < 0.05) and 11% (P > 0.05) of the variation in performance. The first and last STTs were equally fast (228 ± 10 s), and ~ 1.3% faster than the second and the third STTs (P < 0.05). These two fastest STTs were associated with a 14% greater O2 deficit (P < 0.05), while the average V˙O2 was similar during all four STTs (86 ± 3% of V˙O2max). Positive pacing was used throughout all STTs, with significantly less time spent on the first than second course half. In addition, metabolic rates were substantially higher (~_30%) for uphill than for flat skiing, indicating that pacing was regulated to the terrain. CONCLUSIONS: The fastest STTs were characterized primarily by a greater anaerobic energy production, which also explained 69% of the individual variation in performance. Moreover, the skiers employed positive pacing and a variable exercise intensity according to the course profile, yielding an irregular distribution of anaerobic energy production.