title: Effect of skiing speed on ski and pole forces in cross-country skiing.
abstract: OBJECTIVE
  The present study characterized pole and ski forces in classical technique cross-country skiing. Eight elite junior cross-country skiers performed diagonal skiing at 65%, 75%, 90%, and 100% of maximum speed on a stable 100-m-low uphill (2.5 degrees ).
  
  
  METHODS
  : The ski and the pole forces (vertical (Fz) and horizontal (Fy) directions) on the right and left sides were recorded separately when the skier skied over a special custom-made force platform system placed at the end of the uphill course. The entire system consisted of four separate 20-m-long rows of 1-m-long force plates connected in series, row by row.
  
  
  RESULTS
  When the forces were averaged for the various functional phases of skiing cycle, the ski Fz during the gliding phase decreased and the braking ski Fy and Fz remained the same with higher skiing speed. During the subsequent kick phase, both ski Fy and Fz increased significantly as a function of the skiing speed. Consequently, the Fy ratio between the ski and the pole plant increased with faster skiing speed. Simultaneously measured EMGs from five different muscles showed that the abdominals had a pattern of increasing activation with increase in speed of skiing. All the other muscles, vastus lateralis (VL), rectus femoris (RF), erector spinae (ES), and medial gastrocnemius (MG), were obviously active in the preloading and the kick phases.
  
  
  CONCLUSIONS
  The speed dependence of the ski and the pole force distributions in the present study are important for further understanding of the complexity of cross-country skiing. Especially relevant is to use these results as basis for studies aimed at better understanding of the propulsive force production, when more comprehensive EMG analysis is complemented with simultaneous kinematic recordings at varied slope, speed, and waxing conditions.
authors.affiliation: Neuromuscular Research Center, Department of Biology of Physical Activity, University of Jyväskylä, Jyväskylä, Finland. pekka.vahasoyrinki@vuokattisport.fi
authors.forename: Pekka
authors.initials: P
authors.lastname: Vähäsöyrinki
authors.forename: Paavo V
authors.initials: PV
authors.lastname: Komi
authors.forename: Seppo
authors.initials: S
authors.lastname: Seppälä
authors.forename: Masaki
authors.initials: M
authors.lastname: Ishikawa
authors.forename: Veli
authors.initials: V
authors.lastname: Kolehmainen
authors.forename: Jukka A
authors.initials: JA
authors.lastname: Salmi
authors.forename: Vesa
authors.initials: V
authors.lastname: Linnamo
mesh_terms: D000293:Adolescent; D001696:Biomechanical Phenomena; D004576:Electromyography; D006801:Humans; D008297:Male; D018482:Muscle, Skeletal / Q000502:physiology*; D012865:Skiing / Q000502:physiology*; D013647:Task Performance and Analysis