Biomechanical and energetic determinants of technique selection in classical cross-country skiing

Scandinavian Med Sci Sports

Pellegrini

Modena

et al. 2016

This study evaluated muscle activity changes in different body compartments during on-snow double poling at increasing velocities. 21 well-trained, male cross-country skiers performed five 3-min double poling trials on a snowy track at 15, 16.5, 18, 19.5, and 21 km/h (set by an audio-pace system). A sixth trial was performed by maintaining a constant maximal speed. Actual skiing velocities were verified using a photocell system. Only 11 subjects met the pre-defined inclusion criteria during the trials and were included in the data analysis. Electromyographical signals from seven muscles, wrist acceleration and heart rate during the last minute of each trial were recorded. Cycle and poling times were measured from acceleration signals; mean muscular activation over a cycle was calculated for each muscle. With increasing double poling velocities from aerobic to maximal intensity (from 65% to 100% of maximal heart rate), upper limb muscles activation was maintained constant (P > 0.05), while trunk and lower limb involvement increased significantly (P < 0.01) with a linear trend. Rectus abdominis and rectus femoris muscles showed the higher rate of change. Trunk and lower limbs provide a progressively greater contribution to the propulsion when increasing double poling velocities are performed, to support the limited capacity of exercise response of upper body muscles. The remarkable rate of involvement of the muscles near the core region of the body becomes strategic to cope with the increased demands of propulsive power.

Section: Discussionmentioning

confidence: 99%

Changes in upper and lower body muscle involvement at increasing double poling velocities: an ecological study

Scandinavian Med Sci Sports

Pellegrini

Modena

et al. 2016

“…We calculated the duration of the poling action, poling time (PT), as the time between pole ground contact and pole take-off. Because the propulsive action of the leg can occur only when the ski stops with respect to the ground (Nilsson et al, 2004), we calculated leg thrust time (LTT) as the time period during which the ski was still (Bellizzi et al, 1998;Pellegrini et al, 2013). We calculated the speed of the roller skis (v ski ), with respect to the treadmill belt, as the speed along the direction of progression of the marker placed 2 cm in front of the ski binding.…”

Section: Calculation Of Biomechanical Parametersmentioning

confidence: 99%

Gait models and mechanical energy in three cross-country skiing techniques

Pellegrini

Journal of Experimental Biology

Bortolan

et al. 2014

Self Cite

Fluctuations in mechanical energy of the body center of mass (COM) have been widely analyzed when investigating different gaits in human and animal locomotion. We applied this approach to estimate the mechanical work in cross-country skiing and to identify the fundamental mechanisms of this particular form of locomotion. We acquired movements of body segments, skis, poles and plantar pressures for eight skiers while they roller skied on a treadmill at 14 km h −1 and a 2 deg slope using three different techniques (diagonal stride, DS; double poling, DP; double poling with kick, DK). The work associated with kinetic energy (KE) changes of COM was not different between techniques; the work against gravity associated with potential energy (PE) changes was higher for DP than for DK and was lowest for DS. Mechanical work against the external environment was 0.87 J m −1 kg −1 for DS, 0.70 J m −1 kg −1 for DP and 0.79 J m −1 kg −1 for DK. The work done to overcome frictional forces, which is negligible in walking and running, was 17.8%, 32.3% and 24.8% of external mechanical work for DS, DP and DK, respectively. The pendulum-like recovery (R%) between PE and KE was ~45%, 26% and ~9% for DP, DK and DS, respectively, but energy losses by friction are not accounted for in this computation. The pattern of fluctuations of PE and KE indicates that DS can be described as a 'grounded running', where aerial phases are substituted by ski gliding phases, DP can be described as a pendular gait, whereas DK is a combination of both.

“…However, few studies assessed muscle fatigue after prolonged cross‐country skiing (Forsberg et al., ; Viitasalo et al., ; Millet et al., ; Vesterinen et al., ; Cignetti et al., ), observing a marked decrease in the knee extensor (KE) muscles strength (Forsberg et al., ; Viitasalo et al., ; Millet et al., ), together with signs of peripheral fatigue (Millet et al., ). Cross‐country skiing is a competitive endurance sport that involves both the upper and lower limbs, and their contribution varies according to different techniques and track characteristics (Pellegrini et al., ; Holmberg, ). Consequently, one can expect different extent of fatigue between upper and lower limbs.…”

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confidence: 99%

“…Consequently, one can expect different extent of fatigue between upper and lower limbs. Nevertheless, previous studies on neuromuscular fatigue in classical cross‐country skiing investigated mainly the KE muscles (Forsberg et al., ; Viitasalo et al., ; Pellegrini et al., ; Holmberg, ). Moreover, although rapid muscle contractions are essential in all cross‐country ski techniques (Pellegrini et al., ; Holmberg, ), no studies have investigated the effects of fatigue induced by cross‐country skiing on RFD.…”

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confidence: 99%

Central and peripheral fatigue in knee and elbow extensor muscles after a long‐distance cross‐country ski race

Boccia

Dardanello

Scandinavian Med Sci Sports

et al. 2016

Although elbow extensors (EE) have a great role in cross-country skiing (XC) propulsion, previous studies on neuromuscular fatigue in long-distance XC have investigated only knee extensor (KE) muscles. In order to investigate the origin and effects of fatigue induced by long-distance XC race, 16 well-trained XC skiers were tested before and after a 56-km classical technique race. Maximal voluntary isometric contraction (MVC) and rate of force development (RFD) were measured for both KE and EE. Furthermore, electrically evoked double twitch during MVC and at rest were measured. MVC decreased more in KE (-13%) than in EE (-6%, P = 0.016), whereas the peak RFD decreased only in EE (-26%, P = 0.02) but not in KE. The two muscles showed similar decrease in voluntary activation (KE -5.0%, EE -4.8%, P = 0.61) and of double twitch amplitude (KE -5%, EE -6%, P = 0.44). A long-distance XC race differently affected the neuromuscular function of lower and upper limbs muscles. Specifically, although the strength loss was greater for lower limbs, the capacity to produce force in short time was more affected in the upper limbs. Nevertheless, both KE and EE showed central and peripheral fatigue, suggesting that the origins of the strength impairments were multifactorial for the two muscles.