Arnaud Decatoire

Influence of saddle setback on pedalling technique effectiveness in cycling

Abstract Besides its regulation by Union Cycliste Internationale, the evidence relating saddle setback to pedalling performance remains inconclusive. This study investigates the influence of saddle setback on pedalling effectiveness through two indexes: an index of pedalling force effectiveness and an index of pedalling work effectiveness. Eleven cyclists were assessed six saddle setback conditions while pedalling at a steady power output of 200 W and cadence of 90 rpm. A force sensor was integrated within the seat post to compute the centre of pressure on the saddle. From instrumented pedals, an index of force effectiveness (ratio between the force directed perpendicular to the crank arm and the total force applied to the pedal) and an index of work effectiveness (based on the minimisation of negative crank work) were calculated. In comparison with a forward position, sitting backward significantly decreased 5% cumulative total work, increased index of work effectiveness (84.2 ± 3.7 vs. 82.0 ± 4.7%), and increased index of force effectiveness (41.7 ± 2.9 vs. 39.9 ± 3.7 and 36.9 ± 0.7%). Thus, while it was previously reported that sitting more forward favours maximal power, this study demonstrates that it also leads to a decreased effectiveness in steady-state pedalling.

Muscle force strategies in relation to saddle setback management in cycling.

The correct cycling posture consists in both enhancement of the performance and avoiding injuries related to a badly adjusted posture. In particular, several authors underlined that the most common injuries encountered by road racing cyclists (i.e. patellofemoral pain, biceps femoris or quadriceps tendonitis) are related to a badly adjusted fore-aft saddle position (De Vey Mestdagh 1998). The forward-leaning lower limb configuration of the cyclist changes with fore-aft saddle position. Although external cycling power is produced mainly by muscles that span the ankle, knee and hip joints (Martin et al. 2000), these postural constraints probably influence the amplitude and the pattern of muscle forces. Therefore, the changes in muscle coordination strategy related to saddle setback management directly affect lower limb’s ligament and bone-to-bone forces. The purpose of this study was to estimate the effect of changes in fore-aft saddle position on individual muscle forces produced by the cyclist. The main hypothesis was that for a given external power output, a forward position would lead to greater knee extensor muscle forces.

Influence of saddle setback on knee joint forces in cycling

Abstract Knee functional disorders are one of the most common lower extremity non-traumatic injuries reported by cyclists. Incorrect bicycle configuration may predispose cyclist to injury but the evidence of an effect of saddle setback on knee pain remains inconclusive. The aim of this study was to determine the effect of saddle setback on knee joint forces during pedalling using a musculoskeletal modelling approach. Ten cyclists were assessed under three saddle setback conditions (range of changes in saddle position ~6 cm) while pedalling at a steady power output of 200 W and cadence of 90 rpm. A cycling musculoskeletal model was developed and knee joint forces were estimated using an inverse dynamics method associated with a static optimisation procedure. Our results indicate that moving the saddle forwards was not associated with an increase of patellofemoral joint forces. On the contrary, the tibiofemoral mean and peak compression force were 14 and 15% higher in the Backward than in the Forward condition, respectively. The peak compression force was related to neither pedal force nor quadriceps muscle force but coincided with the eccentric contraction of knee flexor muscles. These findings should benefit bike fitting practitioners and coaches in the design of specific training/rehabilitation protocols.

Estudio biomecánico de la carrera a pie

El estudio biomecanico de la carrera a pie ha sido objeto de numerosos trabajos de investigacion. Para que estos sean eficaces, deben emplearse instrumentos de observacion y medicion cada vez mas perfeccionados. El movimiento se evalua en los tres ejes del espacio con recursos tecnicos que incluyen sistemas de analisis de imagenes para la medicion cinematica del movimiento, sincronizados con plataformas de fuerzas para medir los esfuerzos de contacto. Estos dispositivos experimentales, asociados a las leyes de la dinamica de sistemas multicorporales, permiten estudiar en su totalidad y de forma cualitativa y cuantitativa los movimientos realizados por el deportista profesional. La aplicacion de modelos dinamicos, en particular la denominada dinamica inversa, ofrece, por ejemplo, la posibilidad de estudiar magnitudes no mensurables como los esfuerzos accionadores articulares. ystos reflejan la actividad resultante de los musculos generadores del movimiento, interpretada como una autentica firma de la accion efectuada por el atleta. En este sentido, validan y completan los enunciados tecnicos de los entrenadores. Ademas, el conocimiento de estos esfuerzos conduce a establecer dos balances energeticos distintos, en especial el balance que mejor expresa el coste energetico mecanico impuesto por el movimiento. La correspondencia de esta valoracion energetica con la establecida por los enfoques fisiologicos es un tema que apasiona y preocupa a muchos investigadores. Estos trabajos se prolongan en el perfeccionamiento de los modelos musculares, que tambien constituyen un tema de investigacion actual. En otro ambito, el estudio biomecanico de la carrera contribuye a perfeccionar el calzado especifico para esta actividad y a la elaboracion de materiales inherentes a la practica del deporte como los suelos deportivos.

Comparison of motor strategy between confirmed and professional cyclists during an incremental maximal test

The motor strategy used by cyclists is the fruit of training in relation with the pedalling technique. It has been merely considered that mechanical power output at each pedal is related to pedalli...

Comparison of shoulder's net moment between practice and real condition

At the begining of skill training, gymnasts have some difficulties to perform twisting somersaults. Although upper limbs coordination is repeated on the ground, gymnasts are not able to repeat the same movement during somersault. The purpose of this paper was to propose a mechanical explanation of this problem. A comparison of joint dynamics between two gesture was made: on the one hand the upper limbs movement is executed on the ground (T); on the other hand, the same movement is executed during a twisting somersault. Comparison was made with regard to net joint moment because they are responsible to segments movement (Vaughan, 1996). These computations are made on shoulder’s joint.