The effect of chain-ring systems on the performance and pedalling technique in BMX elite and cadet riders

Abstract

BACKGROUND: Sprinting at the start of a BMX race is considered one of the most important determinants of performance. Therefore, different devices and technologies have been developed to improve this ability to sprint, such as non-circular CR (CR) systems. OBJECTIVE: To compare new pedalling performance determinants for the first meters of the acceleration phase in BMX, with two different CR systems, circular and non-circular, in Elite abd Cadet cyclists. METHODS: Two level of BMX cyclists of the Spanish national team – Elite (n= 7), and Cadet (n= 7) – performed two sprints with different CR conditions (circular and non-circular). Each condition was performed in ecological BMX race conditions. Total distance (m), reaction time (s), power output (W) and the ratio between the powers of 90 and 270∘ (local extrema) and the powers at 0 and 180∘ (dead centres) of the pedalling (%PM) were analysed. RESULTS: In Elite group, no differences were found between circular and non-circular CR in total distance, reaction time, and %PM. In the Cadet group, differences were found between circular and non-circular CR conditions in %PM (p= 0.02), resulting in better results for the circular CR. In addition, no differences in total distance and reaction time were found. CONCLUSIONS: The use of non-circular CR system does not result in performance improvement in either Elite or Cadet cyclists.