title: A reduction of the saddle vertical force triggers the sit-stand transition in cycling.
abstract: The purpose of the study was to establish the link between the saddle vertical force and its determinants in order to establish the strategies that could trigger the sit-stand transition. We hypothesized that the minimum saddle vertical force would be a critical parameter influencing the sit-stand transition during cycling. Twenty-five non-cyclists were asked to pedal at six different power outputs from 20% (1.6 ± 0.3 W kg(-1)) to 120% (9.6 ± 1.6 W kg(-1)) of their spontaneous sit-stand transition power obtained at 90 rpm. Five 6-component sensors (saddle tube, pedals and handlebars) and a full-body kinematic reconstruction were used to provide the saddle vertical force and other force components (trunk inertial force, hips and shoulders reaction forces, and trunk weight) linked to the saddle vertical force. Minimum saddle vertical force linearly decreased with power output by 87% from a static position on the bicycle (5.30 ± 0.50 N kg(-1)) to power output=120% of the sit-stand transition power (0.68 ± 0.49 N kg(-1)). This decrease was mainly explained by the increase in instantaneous pedal forces from 2.84 ± 0.58 N kg(-1) to 6.57 ± 1.02 N kg(-1) from 20% to 120% of the power output corresponding to the sit-stand transition, causing an increase in hip vertical forces from -0.17 N kg(-1) to 3.29 N kg(-1). The emergence of strategies aiming at counteracting the elevation of the trunk (handlebars and pedals pulling) coincided with the spontaneous sit-stand transition power. The present data suggest that the large decrease in minimum saddle vertical force observed at high pedal reaction forces might trigger the sit-stand transition in cycling.
authors: University of Toulouse, UPS, PRISSMH, 118 Route de Narbonne, 31062 Toulouse Cedex 9, France. Electronic address: antony.costes@univ-tlse3.fr.
authors: Antony
authors: A
authors: Costes
authors: University of Toulouse, UPS, PRISSMH, 118 Route de Narbonne, 31062 Toulouse Cedex 9, France; Center for Interdisciplinary Research in Rehabilitation (CRIR), Institut de Réadaptation Gingras-Lindsay de Montréal and Jewish Rehabilitation Hospital, Laval, Quebec, Canada.
authors: Nicolas A
authors: NA
authors: Turpin
authors: University of Toulouse, UPS, PRISSMH, 118 Route de Narbonne, 31062 Toulouse Cedex 9, France.
authors: David
authors: D
authors: Villeger
authors: University of Toulouse, UPS, CRCA, 118 route de Narbonne, F-31062 Toulouse Cedex 9, France; CNRS, CRCA, 118 route de Narbonne, F-31062 Toulouse Cedex 9, France.
authors: Pierre
authors: P
authors: Moretto
authors: CNRS, LAAS, 7 Avenue du Colonel Roche, F-31400 Toulouse, France; University of Toulouse, UPS, LAAS, F-31400 Toulouse, France.
authors: Bruno
authors: B
authors: Watier
mesh_terms: D001642:Bicycling / Q000502:physiology*; D001696:Biomechanical Phenomena; D005528:Foot / Q000502:physiology; D006615:Hip / Q000502:physiology; D006801:Humans; D008297:Male; D055595:Mechanical Phenomena; D011187:Posture; D055815:Young Adult
keywords: Inverse dynamics; Pedaling; SEAT; STAND