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Original articles  EXERCISE PHYSIOLOGY AND BIOMECHANICS


The Journal of Sports Medicine and Physical Fitness 2007 Marzo;47(1):40-5

lingua: Inglese

The performance and efficiency of cycling with a carbon fiber eccentric chainring during incremental exercise

Belen L. 1, Habrard M. 1, Micallef J. P. 2, Le Gallais D. 1

1 Motor Efficiency and Deficiency Laboratory UPRES EA 2991 Faculty of Sports Sciences University of Montpellier 1, Montpellier, France
2 Laboratory of Physiology of Interactions INSERM ADR 08, Montpellier, France


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Aim. The aim of this study was to compare cycling performance and efficiency of a carbon fiber eccentric chainring (EC) versus a metallic standard chainring (SC) during an incremental exercise. The main feature of EC was that crank-arm length changed as a function of the crank angle, being maximal during the pushing phase and minimal during the recovery one. Because of its design, cycling with EC was expected to develop higher torque during the downstroke, and lower torque during the upstroke, thus increasing mechanical efficiency and requiring lower cardioventilatory solicitation at submaximal exercise intensities.
Methods. Eleven male subjects performed two incremental cycle tests in a randomized order using EC and SC successively. Cardioventilatory data were recorded every minute using an automated breath-by-breath system. Blood samples were taken at rest, exhaustion, 5 and 15 minutes of recovery to access lactate concentrations, [LA], mmol.L-1 .
Results. The subjects reached significantly lower maximal speed at volitional exhaustion with EC compared with SC (39.4±2.5 versus 41.5±2.9 km.h-1, respectively; P<0.05). Analysis of variance revealed significantly higher values for oxygen uptake and carbon dioxide production during incremental exercise with EC (P<0.05). Lastly, [LA] at exhaustion were similar with the two chainrings.
Conclusion. The carbon fiber EC tested in this study failed to enhance cycling performance and efficiency throughout an incremental exercise. This indicated that carbon fibers did not exhibited its expected mechanical advantage.

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