Anthony Bernard

Kinematic hand parameters in front crawl at different paces of swimming

The aim of this study was to investigate the evolution of kinematic hand parameters (sweepback angle, angle of attack, velocity, acceleration and orientation of the hand relative to the absolute coordinate system) throughout an aquatic stroke and to study the possible modifications caused by a variation of the swimming pace. Seventeen competitive swimmers swam at long distance, middle distance and sprint paces. Parameters were calculated from the trajectory of seven markers on the hand measured with an optoelectronic system. Results showed that kinematic hand parameters evolve differently depending on the pace. Angle of attack, sweepback angle, acceleration and orientation of the hand do not vary significantly. The velocity of the hand increases when the pace increases, but only during the less propulsive phases (entry and stretch and downsweep to catch). The more the pace increases and the more the absolute durations of the entry and stretch and downsweep to catch phases decrease. Absolute durations of the insweep and upsweep phases remain constant. During these phases, the propulsive hand forces calculated do not vary significantly when the pace increases. The increase of swimming pace is then explained by the swimmers capacity to maintain propulsive phases rather than increasing the force generation within each cycle.

Unsteady computational fluid dynamics in front crawl swimming

Abstract The development of codes and power calculations currently allows the simulation of increasingly complex flows, especially in the turbulent regime. Swimming research should benefit from these technological advances to try to better understand the dynamic mechanisms involved in swimming. An unsteady Computational Fluid Dynamics (CFD) study is conducted in crawl, in order to analyse the propulsive forces generated by the hand and forearm. The k-ω SST turbulence model and an overset grid method have been used. The main objectives are to analyse the evolution of the hand-forearm propulsive forces and to explain this relative to the arm kinematics parameters. In order to validate our simulation model, the calculated forces and pressures were compared with several other experimental and numerical studies. A good agreement is found between our results and those of other studies. The hand is the segment that generates the most propulsive forces during the aquatic stroke. As the pressure component is the main source of force, the orientation of the hand-forearm in the absolute coordinate system is an important kinematic parameter in the swimming performance. The propulsive forces are biggest when the angles of attack are high. CFD appears as a very valuable tool to better analyze the mechanisms of swimming performance and offers some promising developments, especially for optimizing the performance from a parametric study.

Experimental and computational studies of the front crawl swimming, at the end of the entry-and-stretch phase

Competitive swimming is a physical codified practice aiming at the achievement of high performances in an aquatic environment. In this context, the swimmer searches to produce themuch important propulsionwhile decreasing the drag forces as much as possible. The front crawl is the most effective swimming, and the role of arms is dominating (Maglischo 2003). Their path is traditionally decomposed into several phases: entry-and-stretch, downsweep-to-catch, insweep, upsweep and exit of water. Every phase has its appropriate function and this sequence of movements produces at present the most effective kinematics. The phase of stretch begins by the entry of the hand into the water and is completed when the opposite hand exits the water. Its path is made in the sagittal plane of progress and can be considered as two dimensional. This phase produces a quasi-steady flow because there are few variations of angles of incidence and velocities. Relatively little interest has been given to this phase, because it is considered as not propulsive and only serves to place segments as forward as possible to create the most ample path (Maglischo 2003). So, the aim of this paper was to study this phase by analysing precisely its role in the global coordination of swimming. The kinematic study will give us the characteristics of the movement, and the dynamic analysis will try to interpret them.

Comparative study between fully tethered and free swimming at different paces of swimming in front crawl

Abstract Tethered swimming is a method often used to measure or enhance the physical and technical resources of swimmers. Although it is highlighted that the technique used in tethered swimming is probably different from that used in free conditions, there are few comparative studies on this subject. The current study aims to compare fully tethered and free swimming based on kinematic hand parameters (orientation, velocity and acceleration of the hand, sweepback and angle of attack), which are known to act directly on the generation of propulsive forces. The results show that there are significant differences during the stretch and catch phases but less during the insweep and upsweep phases. Tethered swimming makes it possible to estimate the propelling forces generated by the hand in free swimming at distance and middle-distance paces, but overestimates it at sprint pace. However, in view of the modifications of the kinematic parameters, it should not be used under repeated conditions of use, such as for the development of swimmers’ capacity.

Analysis of a swimmer’s hand and forearm in impulsive start from rest using computational fluid dynamics in unsteady flow conditions

The propulsive forces generated by the hands and arms of swimmers have so far been determined essentially by quasi-steady approaches. This study aims to quantify the temporal dependence of the hydrodynamic forces for a simple translation movement: an impulsive start from rest. The study, carried out in unsteady numerical simulation, couples the calculation of the lift and the drag on an expert swimmer hand-forearm model with visualizations of the flow and flow vortex structure analysis. The results of these simulations show that the hand and forearm hydrodynamic forces should be studied from an unsteady approach because the quasi-steady model is inadequate. It also appears that the delayed stall effect generates higher circulatory forces during a short translation at high angle of attack than forces calculated under steady state conditions. During this phase the hand force coefficients are approximately twice as large as those of the forearm. The total force coefficients are highest for angles of attack between 40° and 60°. For the same angle of attack, the forces produced when the leading edge is the thumb side are slightly greater than those produced when the leading edge is the little finger side.

Unsteady forces on a hand in swimming in impulsive start configuration

Competitive swimming aims to achieve high performances by the only mechanical action of the swimmer in the fluid at rest. The cyclic action of the arms and legs generates a flow which, by the principle of reciprocal actions (Newton’s 3rd law) acts on the body surfaces. In this context, the hand movement is crucial. The hand propulsive forces directly depend on this flow. Study of these propulsive forces have made mostly from quasi-steady approaches (Schleihauf 1979), and results are commonly given in the form of lift (CL) and drag (CD) coefficients:

The role of the entry-and-stretch phase at the different paces of race in front crawl swimming

Abstract The aim of this study was to determine the role played by the entry-and-stretch phase in the coordination of swimming, at the different paces of race. Three national level swimmers (two men and one woman) were recorded, in lateral and bottom views, in three swimming paces: sprint (50 m and 100 m), middle-distance (200 m and 400 m) and long-distance (800 m and 1500 m). Anatomical landmark positions were obtained by manual digitalisation of the videos. Computational fluid dynamics and experimental studies (with a strain gauge balance and particle image velocimetry method) were used to measure and to calculate the external forces applied to the hand and to the forearm and to visualise the flow around the profile. Entry-and-stretch is the phase which varies the most according to the swimming pace. This phase can be decomposed into two sub-phases: one, the extension forward coordinated with the insweep of the opposite arm, and another one, the rotation downward coordinated with the upsweep. Results show that, at the three paces, this phase is not propulsive and could contribute essentially to maintain the horizontal balance of the body.