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North American Congress on Biomechanics Canadian Society for Biomechanics - American Society of Biomechanics University of Waterloo Waterloo, Ontario, Canada August 14-18, 1998 |
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This study measured kinematic variables during uphill, out-of-the-saddle-cycling (OSC). Researchers have found that the rhythmic lateral oscillation of the bicycle that is part of the natural cycling technique during OSC difficult to replicate accurately in the laboratory. The primary aim of this study was to investigate the kinematics of uphill, OSC to create normative data currently absent from cycling literature.
Forces at the pedals and handlebars have been investigated with a view to explaining differences that arise due to the transition from seated to standing positions (Stone et al., 1993). There is currently a paucity of research quantifying the kinematics of OSC. Furthermore, there have been no attempts made to link kinematic data with kinetic data to form a detailed analysis of cycling in the standing position.
Investigations focussing primarily on OSC have found large differences between forces generated at the pedal and handlebars in seated and standing positions. Handlebar forces, in particular, change as the role of the arms alters from one in which they are stabilisers of the upper body during seated cycling to active contributors of positive force during OSC. Previous studies have alluded to kinematic factors that may become important to force production in a standing position such as the vertical and horizontal translation of the body (Stone et al., 1993) and bicycle tilt (Soden et al., 1979). These studies though, have failed to provide any detailed analysis of the kinematics of the lower extremities during OSC.
The purpose of the current study was to accurately quantify the kinematics pertaining to selected parameters postulated as being critical to the action of cycling, namely the translation of the body in relation to the bicycle and the lateral oscillation of the bicycle. Lower limb kinematics were also quantified. These analyses not only produced normative data for OSC but also showed which of the kinematic elements are most important in determining the hill climbing standard of cyclists.
SUBJECTS: Data were collected outdoors in this study to simulate normal cycling conditions. A slope (10.5% grade) was selected such that the incline was similar in gradient to slopes that would normally cause cyclists to make a transition to a standing position. Sixteen subjects were recruited for the study, forming two groups based on cycling ability. A group of six elite subjects were recruited from the Queensland Academy of Sport and a group of ten non-elite subjects who each usually raced two levels below the elite cyclists were recruited from the cycling club of The University of Queensland.
PROTOCOL: Subjects used the bicycle that they normally rode when racing so that conditions were maintained as close as possible to a race situation. Data collection was performed using video cameras placed both behind the cyclists and perpendicular to the plane of motion of the cyclists. All subjects had spherical markers precisely attached to specific body landmarks to aid in the identification of the necessary sites for digitising. Subjects completed seven trials with five being filmed from the side and two being filmed from the rear. Video data were digitised using the Ariel Performance Analysis Software (APAS) and subsequently analysed with custom code formulated using Matlab.
STATISTICS: Independent sample t-tests were performed across groups for each variable. A discriminant analysis was also performed and the a level was set at 0.05.
Normative data were provided for the translation of the body during OSC as well as for angular movements at the hip, knee and ankle joints. The range of angular displacement at the hip was similar for both groups (68.84 ± 6.72°) as it was at the knee (28.69 ± 8.80°). Maximum (137.40 ± 9.53°) and minimum (96.82 ± 11.07°) ankle joint angles were also similar for both groups although the pattern of angular displacement did show a trend for non-elite subjects to reach a position of maximum plantar flexion earlier in the pedal cycle than elite subjects (Figure 1).
The range of bicycle tilt was also similar between groups although an analysis of maximum (3.72 ± 1.66°) and minimum (-6.60 ± 1.17°) values did show an asymmetric tilt pattern for elite cyclists. Small subject numbers made it difficult to achieve statistical significance, however four variables could be identified that appeared useful in discriminating between the groups. These variables were maximum ankle angle, minimum ankle angle, the range of bicycle tilt and the amount of forward hip translation.
It was found that the transition from seated to standing positions creates large changes to the ranges of motion of the joints of the lower limbs. The angular range of motion at the knee (28.69 ± 8.80°) decreases dramatically from that of a seated position (73.0 ± 6.41°). This large change was caused primarily by the forward translation of the body in relation to the bicycle and also by the fact that some degree of bicycle tilt is introduced into the movement. Changes to the position of the body also appear to affect the angular ranges of the other joints of the lower limbs. The range of motion at the hip (68.84 ± 6.72°) was greatly increased from the sitting position (42.8 ± 4.96°) and the range of motion for the ankle joint (40.58 ± 6.01°) is increased from that of seated cycling (25.7 ± 14.14°) (Too, 1996) (see Figure 2).
The fact that maximum and minimum ankle angles were found to be the best discriminatory tool seems sensible due to the fact that the plantar flexor muscles of the lower leg contribute to force production during OSC more than during seated cycling. This inference was indicated by the much larger range of motion of the ankle joint during out-of-the-saddle efforts. As bicycle tilt has an affect on the kinematics of lower limb joints it seems logical to expect that obtaining an optimum amount of tilt is important to the ability of cyclists to climb. The amounts of forward translation of the hip and bicycle tilt are the two factors most likely to change the ranges of motion of the joints of the lower limbs. Thus it was reasonable to find that they were also among the variables most capable of discriminating between elite and non-elite cyclists' hill climbing ability.
Soden, P. et al. J.Biomech, 12(7), 527-541, 1979.
Stone, C. et al. J.App.Biom., 9, 202-218, 1993.
Too, D. Proceed. 9th CSB biennial conference, 184-185, 1996.
The University of Queensland
The Queensland Academy of Sport
The University of Queensland Cycling Club
