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Fatigue Induced by a Cross-Country Skiing KO Sprint


Medicine & Science in Sports & Exercise: December 2006 - Volume 38 - Issue 12 - p 2144-2150
doi: 10.1249/01.mss.0000235354.86189.7e
APPLIED SCIENCES: Physical Fitness and Performance

Purpose: The aims of the present study were 1) to analyze whether the KO sprint simulation induced a phenomenon of fatigue of upper and lower limbs and 2) if there was any fatigue, to determine its origin.

Methods: Seven elite male skiers were tested before and after a simulation of KO sprints consisting of three 1200-m laps separated by 12 min of recovery. Surface electromyographic activity and force obtained under voluntary and electrically evoked contractions (single twitch) on knee-extensor muscles were analyzed to distinguish neural adaptations from contractile changes. A maximal power output test of the upper limbs was also performed.

Results: During the last lap, the final sprint velocity was significantly lower than during the first lap. After the KO sprint, knee-extensor voluntary (−9.8 ± 9.5%) and evoked (−16.2 ± 11.9%) isometric force and upper-limb power output (−11.0 ± 9.3%) and force (−11.3 ± 8.7%) significantly decreased, whereas the blood lactate concentration increased to 11.6 mM. On the other hand, no changes were seen in RMS measurement during maximal voluntary contractions, RMS normalized by M-wave amplitude, or M-wave characteristics.

Conclusion: Changes in performance, lactate concentration, knee-extensor strength, and upper-limb power indicated that the KO sprint test led the skiers to a state of fatigue. On lower-limb muscles, the decrease of knee-extensor strength was exclusively caused by peripheral fatigue, which was at least in part attributable to a failure of the excitation-contraction coupling.

1Laboratoire de Modélisation des Activités Sportives, Bâtiment Beaufortain, Université de Savoie, Savoie, FRANCE; 2Unité PPEH, Médecine du Sport-Myologie, Hôpital Bellevue, Bellevue, FRANCE; and 3Laboratorio di Ricerca, Centro Inter-Universitario di Bioingegneria e Scienze Motorie Università di Brescia, ITALY

Address for correspondence: Raphaél Zory, Laboratoire de Modélisation des Activités Sportives, Btiment Beaufortain, Université de Savoie, 73376 Le Bourget du Lac, France; E-mail:

Submitted for publication March 2006.

Accepted for publication June 2006.

©2006The American College of Sports Medicine