1,430 research outputs found
Race-time prediction for the Va’a paralympic sprint canoe
The 2016 Paralympic Games in Rio de Janeiro will see 200m sprint canoe events for the first time, using the Va’a class. The aim of this study is to predict race times for the Va’a over a 200m sprint event, through simulation of the hydrodynamic resistance of the hull (with outrigger) and the propulsion provided by the athlete. Such a simulation, once suitably validated, allows investigation of design and configuration changes on predicted race performance. The accuracy of the simulation is discussed through a comparison to times recorded for an athlete over a 200m race distanc
Effects of a sand running surface on the kinematics of sprinting at maximum velocity
Performing sprints on a sand surface is a common training method for improving sprint-specific strength. For maximum specificity of training the athlete’s movement patterns during the training exercise should closely resemble those used when performing the sport. The aim of this study was to compare the kinematics of sprinting at maximum velocity on a dry sand surface to the kinematics of sprinting on an athletics track. Five men and five women participated in the study, and flying sprints over 30 m were recorded by video and digitized using biomechanical analysis software. We found that sprinting on a sand surface was substantially different to sprinting on an athletics track. When sprinting on sand the athletes tended to ‘sit’ during the ground contact phase of the stride. This action was characterized by a lower center of mass, a greater forward lean in the trunk, and an incomplete extension of the hip joint at take-off. We conclude that sprinting on a dry sand surface may not be an appropriate method for training the maximum velocity phase in sprinting. Although this training method exerts a substantial overload on the athlete, as indicated by reductions in running velocity and stride length, it also induces detrimental changes to the athlete’s running technique which may transfer to competition sprinting
Improving sprint performance in road cycling: The forward standing sprint position
The majority of road cycling races finish with a sprint and as such sprints are a key determinant of success. Surprisingly, the scientific literature on this specific topic is scarce, with limited to few studies describing the characteristics of road cycling sprinters and the demands of road sprinting. Cyclists’ sprinting velocity, which is mostly influenced by power output and aerodynamic drag (CdA) is critical to performance outcomes. However, to date, there is very limited research specifically examining how to maximise road sprint velocity. Thus, the overall objective of the four studies outlined in this thesis was to manipulate CdA, physiology, and coaching cues to improve road sprint cycling velocity and performance.
The first study examined the validity of the Velocomp PowerPod, which calculates power output based on opposing/resistive forces experienced. When power output is known (using a direct force power meter), the Velocomp PowerPod is able to calculate a continuous CdA which was the reason why this study was included into this thesis. The research was split in to two separate studies: i) 12 recreational male road cyclists completed a power profile test (5-600 s); and ii) 4 elite male road cyclists completed 13 outdoor cycling training sessions. In both studies, power output of cyclists was continuously measured using both the Velocomp PowerPod and Verve Cycling InfoCrank power meters. The results showed that rolling resistance estimated by the Velocomp PowerPod (0.011 ± 0.0) was higher than what has been previously reported (0.006), which likely occurred due to errors in the subjective selection of road surface type in the device setup. This overestimation of rolling resistance increased the calculated power output, which was significantly greater than the power output measured by the Verve Cycling InfoCrank power meter in both study i and ii (27 to 39% and 16 to 49%, respectively). When rolling resistance was adjusted to previously reported values (0.006), the Velocomp PowerPod power meter was shown to be comparable to the Verve Cycling InfoCrank power meter during a controlled field test (−0.57 to 0.24%) but not dynamic training sessions (8.94 to 33.14%). Consequently, the Velocomp PowerPod power meter was not used in subsequent studies within this thesis.
The following two studies examined the effect of a seated, standing, and novel forward standing (lower and further forward head and torso) sprint position on performance. In study 2, eleven recreational male road cyclists rode 250 m at approximately 25, 32, and 40 km·h−1 and in each of the three positions. Riding velocity, power output, wind direction and velocity, road gradient, temperature, relative humidity, and barometric pressure were measured and used to calculate CdA using regression analysis. Sprinting in a forward standing position resulted in a 23% and 26% lower CdA, when compared with a seated and standing position, respectively. Furthermore, in contradiction with previous research no difference in CdA was observed between a seated and standing position. Additionally, despite no significant difference in CdA between the two test days a poor between-day reliability was observed. In study 3, eleven recreational male road cyclists performed a 14 s sprint in the three different sprint positions before and directly after a 10 min high-intensity lead-up. Peak and mean power output were similar between the forward standing (1126 ± 49 W and 896 ± 33 W, respectively) and both the seated (1043 ± 47 W and 857 ± 29 W, respectively) and standing positions (1175 ± 45 W and 928 ± 29 W, respectively). Collectively the results from studies 2 and 3 indicate that sprinting in the forward standing position may result in an increase in sprint cycling velocity of 5.6-6.5 km·h-1 and 2.1-5.1 km·h-1, when compared with the seated and standing sprint positions, respectively.
In study 4, 28 recreational road cyclists completed a two-week (3 sessions per week) sprint training intervention during which they received either i) visual and external focused verbal instructions, and positive feedback on their cycling sprint position (intervention group), or ii) neutral verbal instructions and feedback (control group). The combination of these coaching techniques did not enhance the training induced improvement in forward standing sprint performance. While improvements in peak (4%) and mean power output (3%), and peak torque (5%) were observed in both groups, it is unclear if these improvements are entirely due to the training programme because of the absence of a non-sprint training control group. This thesis has shown that sprinting in the novel forward standing sprint position could result in an increase of cycling velocity by approximately 5 km·h-1, when compared with more traditional sprint positions. In unaccustomed cyclists, sprint performance in this position might be further improved by a short two-week sprint training programme, however, further research is needed in this area. The results from this thesis have implications in training and tactical decisions of cyclists, coaches, and support staff aiming to be successful in competitive road cycling sprints
Reducing aerodynamic drag by adopting a novel road-cycling sprint position
Purpose: To assess the influence of seated, standing, and forward-standing cycling sprint positions on aerodynamic drag (CdA) and the reproducibility of a field test of CdA calculated in these different positions. Methods: A total of 11 recreational male road cyclists rode 250 m in 2 directions at around 25, 32, and 40 km·h. Results: A main effect of position showed that the average CdA of the 2 d was lower for the forward-standing position (0.295 [0.059]) compared with both the seated (0.363 [0.071], P = .018) and standing positions (0.372 [0.077], P = .037). Seated and standing positions did not differ from each other. Although no significant difference was observed in CdA between the 2 test days, a poor between-days reliability was observed. Conclusion: A novel forward-standing cycling sprint position resulted in 23% and 26% reductions in CdA compared with a seated and standing position, respectively. This decrease in CdA could potentially result in an important increase in cycling sprint velocity of 3.9-4.9 km·
A Novel Approach of Modelling and Predicting Track Cycling Sprint Performance
In cycling, performance models are used to investigate factors that determine performance and to optimise competition results. We present an innovative and easily applicable mathematical model describing time-resolved approaches for both the physical aspects of tractional resistance and the physiological side of propelling force generated by muscular activity and test its validity to reproduce and forecast time trials in track cycling. Six elite track cyclists completed a special preparation and two sprint time trials in an official velodrome under continuous measurement of crank force and cadence. Fatigue-free force-velocity profiles were calculated, and their fatigue-induced changes were determined by non-linear regression analysis using a monoexponential equation at a constant slope. Model parameters were calibrated based on pre-exercise performance testing and the first of the two time-trials and then used to predict the performance of the second sprint. Measured values for power output and cycling velocity were compared to the modelled data. The modelled results were highly correlated to the measured values (R2>0.99) without any difference between runs (p>0.05; d<0.1). Our mathematical model can accurately describe sprint track cycling time trial performance. It is simple enough to be used in practice yet sufficiently accurate to predict highly dynamic maximal sprint performances. It can be employed for the evaluation of completed runs, to forecast expected results with different setups, and to study various contributing factors and quantify their effect on sprint cycling performance
Fluid Power Vehicle Challenge
The FPVC combines mechanical engineering disciplines to design and manufacture a vehicle that utilizes hydraulic power. The FDR covers the final manufacturing process and verification processes developed during the front end of research and analysis built upon the Critical Design Review (CDR) and the PDR (Preliminary Design Review). This report showcases the design decisions and extensive research that supports the continuing efforts by the Team Pump My Ride, to build upon the accomplishments of Cal Poly’s previous team, The Incompressibles. The FDR presents how Team Pump My Ride produced the design changes from the CDR and PDR to achieve improvements to the vehicle’s performance. The FDR is detailed with the procurement methods, validation procedures, results, conclusions, recommendations for next year’s team. In addition, details about the virtual competition are included in this report. Major changes that were made during manufacturing included reconstruction of the rear drive train, installation of the new manifold with soft lines, mounting the controller unit, re-designing the controller software and hardware, installation of new bike tires, and re-orientating the accumulator. Testing that was completed include a full trial run for competition as well as testing different pre-charge pressures. In addition, a user manual was developed in order to aid the next team’s members to operate the bike. This report proceeds to conclude team Pump My Ride’s efforts to improve the vehicle and finish as a high-ranking competitor in the 2020 Fluid Power Vehicle Challenge.
Disclaimer: This report is meant to be used as a guide for basic orientation with the 2020 Cal Poly Fluid Powered Vehicle. This is a dangerous machine that can cause grave bodily injury if misused. This report is in no way complete and should not be treated as such. High pressure hydraulics are inherently dangerous, and care should be taken whenever in the vicinity of the vehicle. Likewise, the Li-Po battery used on this project must be fully understood to prevent injury or fires. By using the vehicle, you take full responsibility for your safety and the safety of those around you
Experimental and Numerical Analysis of a Sprint Canoe for the Olympic Games
Portuguese culture has always been interconnected with nautical culture. Nowadays, Portugal is a powerful country in canoeing. Besides athletes, excellent training places, Portugal is
one of the best manufacturers of canoes and kayaks in the world. To have a constant evolution in the design of the boats, it is crucial to study the hydrodynamics of canoes. Therefore,
the present work arises in the context of the lack of scientific studies in the area of hydrodynamics in canoeing, mainly the C1 boat.
In this dissertation, simulations of Computational Fluid Dynamics (CFD) were performed
in order to simulate the water and air flow around the hull of two canoes to evaluate their
performance. For this, the Fluid Volume method (VoF) was used to simulate the free surface,
and the turbulence model ?Âe Standard to simulate the turbulence. A mesh independence
study was also carried out to ensure that the mesh used does not affect the intended results.
The software used for this analysis was Ansys Fluent 2019 R3.
In order to validate the numerical study, experimental tests were performed at full scale. The
numerical model was then applied to the two vessels, where the resistance to advance of the
canoes, at a range of velocities was studied, as well as for different pitch angle.
Also for comparison purposes the wave elevation, as well as the effect of the flow velocity, in
both canoes were evaluated.
For the C1 5 L model, the values were overestimated numerically, while for the other model,
the C1 8 L, the results were closer to the values obtained experimentally. Other numerical
studies have shown similar problems, which possibly has to do with the exact determination
of the waterline position, which significantly influences the final results.A cultura portuguesa esteve sempre interligada com a cultura náutica. Atualmente, Portugal
é uma potência na modalidade de canoagem. Para além de atletas, excelentes locais de treino,
Portugal, é um dos melhores fabricantes de canoas e kayaks a nÃvel mundial. Para haver
uma constante evolução dos designs dos barco, é crucial estudar a hidrodinâmica das canoas.
Assim, este trabalho surge no âmbito da falta de estudos cientÃficos na área da hidrodinâmica
na canoagem, principalmente da embarcação C1.
Nesta dissertação foram realizadas simulações de Dinâmica de Fluidos Computacional (CFD),
com o objetivo de simular o escoamento de água e ar em torno do casco de duas canoas, para
avaliar a performance destas. Para isso, foi utilizado o método do Volume de Fluido (VoF)
para simular a superfÃcie livre, e o modelo de turbulência ?Âe Standard para simular a turbulência. Foi também realizado um estudo de independência de malha para garantir que a
malha utilizada não afeta os resultados pretendidos. O software utilizado para esta análise
foi o Ansys Fluent 2019 R3.
Com vista a validar o estudo numérico, foram realizados testes experimentais à escala real.
O modelo numérico foi então aplicado às duas embarcações, onde foi estudada a resistência
ao avanço das canoas para uma gama de velocidades, assim como para diferentes arfagens.
Também para efeitos de comparação foram avaliadas a elevação de onda, assim como o efeito
da canoa nas velocidades do escoamento em ambas as canoas.
Para o modelo C1 5 L, os valores foram sobrestimados numericamente, enquanto que para
o outro modelo, a C1 8 L, os resultados foram mais próximo dos valores obtidos experimentalmente. Outros estudos numéricos demonstraram problemas semelhantes, o que possivelmente terá a ver com a determinação exata da posição da linha de água, que influencia significativamente os resultados finais
Riding against the wind: a review of competition cycling aerodynamics
Aerodynamics has such a profound impact on cycling performance at the elite level that it has infiltrated almost every aspect of the sport from riding position and styles, equipment design and selection, race tactics and training regimes, governing rules and regulations to even the design of new velodromes. This paper presents a review of the aspects of aerodynamics that are critical to understanding flows around cyclists under racing conditions, and the methods used to evaluate and improve aerodynamic performance at the elite level. The fundamental flow physics of bluff body aerodynamics and the mechanisms by which the aerodynamic forces are imparted on cyclists are described. Both experimental and numerical techniques used to investigate cycling aerodynamic performance and the constraints on implementing aerodynamic saving measures at the elite level are also discussed. The review reveals that the nature of cycling flow fields are complex and multi-faceted as a result of the highly three-dimensional and variable geometry of the human form, the unsteady racing environment flow field, and the non-linear interactions that are inherent to all cycling flows. Current findings in this field have and will continue to evolve the sport of elite cycling while also posing a multitude of potentially fruitful areas of research for further gains in cycling performance
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