PEDALING ANALYSIS IN BMX BY TELEMETRIC COLLECTION OF MECHANIC VARIABLES

Ano: 2007 | Volume: 1 | Número: 2

Autores: Philippe Campillo, Timothee Doremus, Jean-Michel Hespel

Palavras-chave: cycling, crank arm, power

Resumo Inglês:

CAMPILLO, P.; DOREMUS, T.; HESPEL, J.-M. Pedaling analysis in BMX by
telemetric collection of mechanic variables. Brazilian Journal of Biomotricity. v.
1, n. 2, p. 15-27, 2007. The purpose of the study was to analyze the influence of
crank lengths of the pedals on several kinematic and dynamic variables of
pedaling. Nine national or international level subjects performed 3 series of 3
consecutive accelerations of 20 meters with 3 different crank lengths: 175, 180
and 182 mm. A telemetric acquisition system conceived and adapted
specifically to an experimental BMX made it possible to collect the data of 2
dynamometers placed on the transmission crown and 2 velocity pick-ups fixed
at the level of the teeth of the crown and the back hub. The results showed that
on an acceleration phase of 20 m, linear velocities of the BMX equipped with
cranks of 182 were significantly (P<0.001) higher Vb182 (6.8 ± 2.4 m.s-1) and
Vb175 (5.8 ± 1.9 m.s-1). These results were the consequence of angular
velocities significantly different in P<0.01 ωp182 (10.3 ± 4.3 rad.s-1) and ωp175
(9.4 ± 4.8 rad.s-1), which was not the case for the forces Fp175 (641.3 ± 190.6 N)
and Fp182 (604.3 ± 210.9 N). These results allowed some of these sportsmen to
reconsider the use of 182 mm cranks.