Flows around a swimmer's body in a prone glide position are computed with a Computational Fluid Dynamics (CFD) technique in order to understand the effect of a body shape on flow characteristics. A human model which consists of artificial bones, joints and an overlying skin is used to model the body shape in the consistent form via manipulation of the joints. A finite-volume based Navier-Stokes solver is used with unstructured tetra, prism and hexahedral grids for the flow computation to cope with the complicated geometry of a human body. The computed results of the underwater swimming show that the pressure drag is more than six times larger than the frictional drag. Various types of longitudinal vortices, flow separations and reattachments are observed due to the concave and convex geometry of the body. The parameter study for the gliding depth is conducted to evaluate the free-surface effects and the wave making resistance. The deformation of free-surface is computed reasonably well and it is shown that the wave making resistance can be estimated by the CFD technique.
The present study investigated the attitude of exercise adherence and aquatic environment in swimming across Lake Kasumigaura. The participants were 60 males and 17 females (23-77 years) who completed a questionnaire survey. The questionnaire was composed of 27 items that represented 6 categories: self-efficacy, exercise-induced feeling, self-esteem, exercise adherence, participation meaning, and aquatic-environmental attitude. The results indicated that the participants had a positive feeling for efficacy of swimming, physical self-perception and exercise adherence, and got a significant concern for aquatic environment. It suggests a possibility that swimming across a lake leads to the change of attitude not only exercise adherence but also preserving nature and enjoying swimming in open water such as a lake.
The purpose of this study was to examine the hand reaction force in backstroke start including new backstroke grip positions. The subjects were elite-backstroker (n=6). The instruments consisted of backstroke grip on water proof force platform. Two-dimensional motion analysis technique was used to collect motion data. As result, there were two peaks (peak 1 and peak 2) in the elite swimmer's hand reaction horizontal force. Elite swimmers pulled the grip strongly at peak1. The results suggest that the pulling a grip is important skill in backstroke starts. And in the comparison of the grip positions, significant differences were found between horizontal lower grip at peak1 and other grip at peak1 (p<0.05), however horizontal lower grip showed the slowest transition time at 5m. This study was the first to investigate hand reaction force during backstroke start motion. The data in the present study was contrary to the describing reported by many coaching books.
The purpose of this study was to develop a method to predict fluid forces acting on the foot and to clarify those characteristics during breaststroke kicking motion. Three male competitive swimmers whose specialties were breaststroke participated in this study. They performed breaststroke kicking motion without upper limb motion at three different effort trials (Slow, Normal, Fast). The trials were recorded by digital video cameras (60Hz) and we calculated coordinates of a right foot by using 3D-DLT method. Eight pressure sensors (200Hz) were attached on the right foot of swimmers and measured pressure distribution. Fluid forces acting on the foot were obtained by the way of multiplying measured pressure value and area of foot. As a result, fluid forces acting on the foot reflected the motion of foot. Furthermore, we found differences of influence by the change of effort each of subjects.