Test bike bench design for 3d kinematic and kinetic optimisation in cycling
- Joaquín Ojeda Director
- Juana María Mayo Núñez Director
Defence university: Universidad de Sevilla
Fecha de defensa: 19 April 2023
Type: Thesis
Abstract
The main objective of this thesis was to solve the 3D inverse dynamic problem during cycling. For this purpose, the procedures used for motion capture using videogrammetry were adapted to the practice of cycling. In addition, modifications were made to a commercial bicycle in order to measure the forces applied to it. In order to achieve the objective, the first of the studies carried out in this thesis was the 3D lower body movement analysis during pedalling. The complexity of accurately measuring movements outside the sagittal plane (plane parallel to the bicycle frame), caused the number of studies focusing on 3D kinematic analysis of cycling to be limited. The studies that opt to analyse kinematics outside the sagittal plane tended to use marker protocols from gait analysis, which did not take into account the cycling particularities. Due to the lack of a specific marker protocol for cycling, one of the aims of this thesis was to develop and evaluate a new marker protocol with which to carry out a 3D kinematic analysis in cycling at the level of position, velocity and acceleration in a simple way and without affecting the comfort of the participant. Because there is no gold-standard of 3D pedalling kinematics accepted by the scientific community, the results obtained have been evaluated by physiological and comparative analysis with previous works. The results obtained were similar to those in the literature, with low intra-subject variability in the sagittal and transverse planes and a high repeatability of the order of that reported by other protocols for gait analysis. Velocity and acceleration results outside the sagittal plane suggested their importance when considering them in the resolution of the inverse dynamic problem. To solve the inverse dynamic problem in the lower body, in addition to the movement of this, the 3D force applied to the pedals had to be known. To obtain this force, the most commonly used equipment tended to focus only on the components contained in the sagittal plane, which means that one of the components of the force was disregarded. On the other hand, equipment intended to measure all three components of force tended to be bulky and heavy, which could affect the naturalness of pedalling. In this work an equipment capable of measuring the three components of the force applied to both pedals, with a reduced mass and size, has been developed and evaluated. The results obtained when measuring the pedalling forces were similar to those shown in the literature. The correct estimation of the lateral-medial direction force was of great interest to assess possible joint overload. The temporal evolution of the total power over the pedalling cycle was also estimated with values also similar to the literature. Once a procedure for obtaining the 3D motion of the cyclist and calculating the three components of the force applied to the pedals was available, the 3D dynamics analysis during pedalling was possible. In the literature, most of the works that carry out a dynamic analysis of pedalling focused on the sagittal plane. Few studies performed a 3D dynamic analysis and those that carried it out, did not study all the joints that form the lower body. In this thesis, the 3D inverse dynamic problem was solved for the three joints that make up the lower body using the bottom-up methodology. In order to carry out this study, the marker protocol designed in this thesis and the force measurement equipment installed in both pedals were used. Additionally, a process had to be designed to synchronise the kinematic data and the forces applied to the pedals. As a result, joint moments and forces and joint-specific powers were obtained, but they could only be partially evaluated due to the limited information available for data outside the sagittal plane. Those results that could be compared showed significant similarities with the published results. The study of cycling dynamics showed that the pedalling ability of the participants analysed had a notable effect on the results obtained. In addition to the main objective, this thesis also carried out other types of studies applying the knowledge obtained in the processes described above. One of these studies was the analysis of the asymmetries in the forces applied to the pedals by both legs. This study was important because the asymmetries may affect the performance of the cyclist or prevent the occurrence of injuries. Studies focused on analysing asymmetries in forces tend to consider only the effective force, disregarding the three-dimensional nature of the force. Another characteristic of these studies was that they tend to analyse asymmetries using significant scalar data, such as the maximum value of the force or the range. This way of operating can also hide information. Therefore, in this thesis the analysis of the asymmetries for the three components of the force evaluated at all the instants of the pedalling cycle was carried out using the normalised symmetry index and the cross-correlation coefficient. The combination of both indices not only made possible to detect if there were asymmetries, but also the possible cause of these asymmetries: differences in force levels and/or time lags in the temporal evolutions of the forces applied by each leg. Forces in the sagittal plane showed a high level of symmetry. The lateral-medial force presented the highest level of asymmetry due to the difference in the magnitudes of the applied forces by both legs and the existing time shift between the two force patterns. Another application of the knowledge obtained in this thesis was the analysis of the effect of pedalling power on joint angles, forces and moments and joint-specific powers. This type of study has been carried out in the literature focusing on the sagittal plane and using scalar variables (ranges, maximum or minimum values). This way of working causes loss of information, as well as not identifying in which instants or phases of the cycle the pedalling power used has the greatest effect. In this thesis, the effect of using different pedalling powers on the variables mentioned above was analysed using three different pedal powers (170 W, 240 W and 310 W). All the variables were analysed in a 3D way and throughout the whole pedalling cycle (vector variables). The study of the effects of power was carried out by analysis of variance using the statistical parametric mapping methodology. From these statistical analyses the conclusion was that pedalling power did not affect kinematics. Joint moments and forces were the variables most sensitive to pedalling power, while the knee was the joint that showed the greatest sensitivity to changes in pedalling power. For joint moments, significant differences were obtained for all three anatomical planes. Similarly, joint forces also showed significant differences in the three directions of space. For both variables, the instants where the greatest differences occurred were near the top or bottom dead centre or the zone of maximum force application. As a final part of this thesis, the conclusions reached were presented together with the limitations presented in the different studies carried out. Additionally, the contributions of this thesis to scientific journals and congresses were listed together with the future lines of research.