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The objective of this study was to develop a comprehensive method for musculoskeletal simulation in swimming. In the developed method, the motion capture data of a swimming motion were first transformed into input data for the swimming human simulation model Swimming Human Model (SWUM). Then, the output data from SWUM were transformed into input data for the musculoskeletal simulation. In order to examine the validity of the developed method, the musculoskeletal simulations of the crawl and breaststroke by two swimmers were conducted. Based on the results of the crawl, the muscles of the upper limbs were activated significantly at the pull and push phases. The swimmer also adjusted the swimming speed, not by changing the effort of the upper limbs during the pull and push phases but by changing the length of the entry phase and the effort of the flutter kick. The results of the breaststroke showed that the muscles of the lower limbs were activated significantly at the kick phase. The swimmer adjusted the swimming speed, not by changing the effort of the upper limbs but by changing the length of the glide phase and the effort of kicking. The results from this study were consistent with the findings in previous studies, except for the period of large (nearly 180 degrees) flexion or abduction at the shoulder joint. The results also revealed the strategies of the swimmers to adjust their swimming speed. This indicates the promising potential of the musculoskeletal simulation, that is, it will be possible to estimate the strategy of a swimmer by conducting the simulation.

Compression garments are widely used in various sports activities. Since the cloths in a compression garment are sufficiently attached to the human body, it is possible for a compression garment to have particular mechanical functions by appropriately arranging the tension distribution in the garment. However, the effects of such garment on muscle activity have not been sufficiently investigated yet. Therefore, a method of musculoskeletal simulation for such problems were developed in the present study. In the developed musculoskeletal model, particular belt-like parts of cloths which had larger tension against stretch were modelled as virtual ligaments. In order to distribute the virtual ligaments, 403 reference points for upper half of the body were defined on the whole body in the musculoskeletal model. These points could be used as start, end and via points for the virtual ligaments. As an example of analysis, a running motion was analyzed in the present study. The running motion was acquired from the experiment using motion capture system, and put into the simulation model. One simple pattern of tension distribution was examined by the simulation. From the simulation, it was confirmed that the muscle activity changed according to the tension of the belt-like cloths. Therefore the developed simulation method will be useful for the design (the arrangement of the belt-like cloths) of the whole body compression garments.

Every year, recreational distance running gains in popularity, with about 15% of the Western population that often goes for a run. The majority of the runners seem to prefer short distances, since ...

In this study, a numerical design method for high-performance sports spats was proposed. The effect of sports spats on the human body during running motions was calculated. An anisotropic hyperelastic model considering stress softening was implemented to reproduce the mechanical characteristics of the sports spats fabric. Also, cyclic tensile loading tests were conducted to evaluate the mechanical characteristics of the sports spats fabric, which was composed of tricot fiber. The stiffness changed with loading direction, and the stiffness was softened depending on previous maximum stretch. The material parameters of the sports spats were identified using the cyclic loading test results. The theoretical calculations showed good agreement with experimental results. The anisotropic hyperelastic model was applied to a 3D-CG human model and running motion data were also introduced into the human model. The proposed numerical design method enabled calculation of the stress induced by the sports spats during running motions. Also, the joint torque generated in each knee was calculated using the stress calculation. The effect of high-performance sports spats on the human body was thus evaluated numerically.

Recently, there have been many developments in compression sportswear and swimwear. The main purpose of compression sportswear is to keep athletes’ muscles warm to prevent muscle strain and fatigue. Now, some compression sportswear has been developed to include a joint protection function. In this study, a design method for joint torque generated by compression sportswear such as competitive swimwear and compression long running tights is proposed. Information on the joint torque generated by sportswear would be useful for compression sportswear design. The proposed method calculates stress-strain relationships of sportswear fabrics using the anisotropic hyperelastic model, and calculates the frictional displacement between the human body and sportswear using a 3D-CG human model. In order to accurately calculate stress, anisotropic material modeling and a stress-softening model were applied to the mechanical characteristics of compression sportswear fabrics. The frictional displacement between the human body and swimwear during swimming was also considered for stress calculations. Typical sportswear fabrics exhibit anisotropic mechanical behavior depending on tensile direction. Also, the stiffness of the fabrics is softened by the maximum strain experienced in each warp and weft fiber. To accurately calculate the joint torques generated by compression sportswear, the anisotropy and stress softening of sportswear fabrics are considered for numerical modeling.

The purpose of this study is to develop a new method for designing compression sportswear from the viewpoint of force by simulation. Applied simulation techniques are 1) skin strain simulation, 2) fabric strain simulation using the anisotropic hyperelastic model, and 3) musculoskeletal simulation. For skin strain simulations, a three dimensional computer graphic (3D-CG) polygon strain was calculated as a skin strain using a 3D-CG model that simulates the human body (CG-Human-Model). The initial strain and the strain caused by physical exercise were given to the polygon model representing the shape of the sportswear (CG-Sportswear-Model). For compression sportswear, the strain of the fabric is approximately the same as skin strain, thus the strain of the CG-Human-Model was given to the CG-Sportswear-Model. In-plane and out-of-plane forces resulting from the CG-Sportswear-Model are calculated using anisotropic hyperelastic models. These forces were given to the musculoskeletal simulation as the external forces, and muscle activity required for any given physical exercise (e.g. swimming motion) was calculated. Information of forces and muscle activity are very useful in designing compression sportswear. It is believed that this new method for designing compression sportswear based on simulation is a sophisticated technique because this method takes into account not only forces resulting from sportswear but also the effect of these forces on physical exercise.

A new design method for designing competitive swimsuits using 3-dimensional stress calculation was investigated in this paper. An anisotropic hyperelastic modeling of swimwear fabric was developed from the results of tensile loading tests. 3-dimensional stress distributions of swimwear in swimming motions were calculated by the anisotropic hyperelastic model. The displacement fields of 3D-CG human model which reproduce swimming motion of human body were applied to stress calculation. For the material modeling, the uniaxial cyclic tensile loading tests were conducted to obtain the mechanical characteristics of competitive swimsuits. From loading test results, the mechanical characteristics of swimwear fabrics show strong-anisotropy and the stiffness of the fabric shows hardening along with the increase of stretch. The cyclic tensile loading test results shows reduction of stiffness which depended on the maximum deformation previously reached in the history of the material. To take the strong anisotropy and stress reduction into account for the material modeling, a stress-softening model for anisotropic hyperelastic model using stiffness ratio of warp or weft was proposed. The results of the simulation showed good agreement with that of pressure test in a design range of competitive swimsuits. Finally, 3-dimensional stress distributions of swimwear were calculated by the proposed anisotropic hyperelastic model. A polygonal model of the swimwear was prepared and deformation of swimwear was adapted to the skin of 3D-CG human model in swimming motions. From the results, stress distributions were able to be visualized on the 3D-CG swimwear model.

The objective of this study was to develop a musculoskeletal simulation for a swimmer wearing competitive swimwear. For the simulation, the body geometry and joint motion were put into the swimming human simulation model SWUM in order to calculate the distributed fluid forces acting on the whole swimmer's body. The distributed fluid forces were put into the musculoskeletal model. In addition to the fluid forces, the forces induced by the tension of the swimwear were also considered. As an example, the simulation for the crawl stroke was conducted. The results showed the time-varying effect of the swimwear on the muscle activity during swimming.

The purpose of this study is development of a new design method for competitive swimwear by numerical simulation. Biaxial tensile loading tests were conducted to obtain the mechanical characteristics of competitive swimwear. The fabrics of competitive swimwear consist of chemical fiber. Therefore, the fabrics show anisotropic characteristics that depend on the fiber orientation angle. From biaxial tensile loading test results, the fabric has orthotropy and the stiffness of the fabric shows the graph like the two polygonal lines along with the increase of stretch. An anisotropic hyperelastic model was applied to the reproduction of mechanical characteristics of swimwear. The anisotropic hyperelastic model in this paper is able to adjust the axial and shear stiffness individually. The material parameters of the anisotropic hyperelastic model for the finite element simulation were determined from biaxial tensile loading test results. And then, finite element simulation of tensile loading tests was conducted to show the applicability of our design method to competitive swimwear. In finite element analysis, the bias of deformation and stress distribution by the anisotropy were reproduced. It is important to design the pressure given by stretch of competitive swimwear from the two viewpoints, the exercise performance and the burden to the heart function. We estimated the pressure caused by wearing competitive swimwear against the human body using a simple cylinder model.

The purpose of the present study was to compare the impedance derivative waveforms using spot and band electrode array and to assess applicability of automated signal processing system for cardiac output kinetics. Five healthy male subjects were tested. Cardiac output (Q) were measured using spot electrode array. Each subject performed rest-exercise transitions in leg and arm exercise on an electrically braked ergometer. The intensities of leg exercise were 25, 50, and 100 W for 5 min and those of arm exercise were 25 and 50 W. Comparisons between spot and band electrodes were made for the absolute magnitude of Q and stroke volume (SV), as well as for impedance derivative waveforms. The waveforms for spot electrodes showed less fluctuation by breathing and movement artifacts than for band electrodes. Q for spot electrodes were larger than those for band electrodes. There was a significant correlationship between oxygen uptake (Vo2) and Q. There was a significant correlationship between Q using spot electrode and Q measured by CO2 rebreathing method. Nonlinear correlation coefficient to exponential curve of Q kinetics for leg exercise was more than 0.7 and for arm exercise more than 0.4 in spite of large movement of upper body. It is suggested that the present system using spot electrodes is superior in signal processing to those for band electrodes and able to evaluate Q kinetics without multiple repetition of exercise tests.

1) We evaluated the method for calibrating the pneumotachograph according to flow rate by the software on personal computer. Flow volume was detected using the approximated equation (y = 1.294x2 + 0.989x + 35.824, r = 0.976, p less than 0.01) from various mean flow rate and integration of output voltage. The error between syringe volume (21) and the estimated value on the equation was 10 +/- 8 ml (0.48 +/- 0.42%). 2) Using the method described in 1), we developed computer-controlled-system for assessing respiratory gas exchange by mixing chamber method. To evaluate the accuracy of the system as compared with the Douglas Bag method, we measured the gas parameters of the both methods for two male subjects at rest(3 and 5min) and steady state exercise (3 min., 60-240watt). The error between the both methods were within +/- 5% in ventilation(VE), mixed expired O2 (FEO2) and CO2 (FECO2) concentration, and were within +/- 8% in O2 uptake(VO2) and CO2 production (VCO2). There were high positive correlation (r greater than 0.99, p less than 0.01) between the both methods in the all parameters. These results indicate that the system in this study would be practical use, that VE can be measured in only one pneumotachograph, even if the range of flow rate was wide(e.g. from rest to heavy exercise).

It has been reported that respiratory frequency (F) serves to determine anaerobic threshold (AT). The purpose of this study was to investigate whether the method detecting AT by using F is influenced by the subject's condition such as the existence of sport experiences. Ten healthy adults volunteered to perform progressive cycle ergometer exercise with workloads increased by 30-W (female:20-W) every 2 min at 60 rpm. VO2 at AT were determined by four different methods, which detect the point of 1)nonlinear increase in VE, VCO2, and increase in VE/VO2 without increasing in VE/VCO2 (AT-v), 2) nonlinear increase in F (visual estimation: AT-VF), 3) inflection in F by multisegment linear regression (AT-CF), 4) inflection with omitting above RC point as with 3) (AT-CF2). The mean VO2 at AT-VF (40.8 +/- 9.2 ml/kg/min) and AT-CF (42.7 +/- 9.9 ml/kg/min) was significantly higher compared with AT-V (28.2 +/- 10.4 ml/kg/min) and not RC (42.3 +/- 10.0 ml/kg/min). It would be possible that AT-VF and AT-CF indicated RC, but not AT. There were no significant differences between AT-CF2 (28.2 +/- 10.9 ml/kg/min) and AT-V, and a highly positive correlation (r = 0.79, p less than 0.05) was observed between them. It was recognized that F reached a plateau at AT in four of the subjects. The error between AT-V and AT-CF2 was observed individual variations and the error between them within 5% was observed in only one subject. These results suggest that F is inadequate as an indicator of the AT, because F may be influenced by entrainment of breathing and pedalling frequency.

This paper investigates an engineering approach using numerical analysis on a new constitutive model of the competitive swimwear. First, an anisotropic hyperelastic model was proposed. It reproduces the mechanical characteristics and its material modulus are estimated by the biaxial loading test. From this biaxial loading test, the fabrics for competitive swimwear have shown nonlinear elasticity which is regarded as hyperelasticity like rubber. In addition, they also have shown anisotropic characteristic which is dependent on the directions of warp and weft yarn. An anisotropic model is represented by the power series of invariants of stretch and shear deformation in each yarn. In order to verify the reproducibility, the material parameters of the proposed model were determined by nonlinear least squares approximation and the theoretical value was introduced. Second, from the cyclic loading test results, the materials have shown the viscosity and stress-softening effect. We proposed softening model for cyclic deformation.