INTRODUCTION: The muscle recruitment pattern during alpine skiing is special and characterized by a preponderance of eccentric (lengthening) over concentric (shortening) activity (Berg & Eiken 1999). Eccentric contractions have specific physiological characteristics which have not been studied nearly as well as those of concentric muscle contractions. The key features of eccentric contractions are a much lower (approx. fourfold) metabolic requirement for a given (negative) power requirement combined with a close to twofold reduced recruitment of motor units, ie. smaller EMG activity, for a given (negative) torque. It is surprising that in general, training regimes in alpine skiing have not been tailored to more specifically address the problem of improving and controlling eccentric contractions. METHOD: We have built an eccentric (reclining seat) ergometer that is Software controlled, can deliver a maximum of S'OOO W of power, uses a biofeedback System to adjust training loads, allows for quantitative assessment of required vs. applied power (coordination) and has a number of safety features preventing catastrophic overload of the athlete musculoskeletal System. We have used the eccentric ergometer in various training settings with patients (cardiac and orthopaedic rehabilitation) as well as with junior and elite alpine skiers and selected other athletes. Training outcome was assessed by using a force platform, estimating muscle volume (by DEXA) and analyzing muscle biopsies with morphometric and molecular techniques. RESULTS: Selected results from alpine skiers indicate that: - six weeks of eccentric exercise training increases Jump heights in counter movement Jumps by 7.9% (+4.1 cm). - after five 20-minute eccentric exercise sessions eccentric training load can be increased by over 100% (from 397 to 822 watts) in elite Slalom skiers, without muscle soreness. - the estimated coordination of eccentric force development was best in those athletes with the best world rank position in slalom - all athletes are able to massively improve coordination of eccentric force development already after the second training bout DISCUSSION and CONCLUSIONs: Our results indicate that the quality of eccentric force development can be measured by the use of an eccentric ergometer and that eccentric force and coordination can be improved in elite alpine skiers. The eccentric mode of muscle action during alpine skiing requires high power generating leg and trunk muscles and coordination for eccentric muscle activity. Eccentric exercise training therefore appears to be a promising approach to improve performance and prevent injury in alpine skiers
© Copyright 2008 Science and Skiing IV. Veröffentlicht von Meyer & Meyer. Alle Rechte vorbehalten.