Biomechanics and Medicine in Swimming XI

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An Analysis of the Underwater Gliding Motion in Collegiate Competitive Swimmers Wada, t. 1 , sato, t. 2 , ohishi, K. 2 , tago, t. 3 , Izumi, t. 1 , Matsumoto, t. 1 , Yamamoto, n. 4 , Isaka, t. 5 , shimoyama, Y. 6 1 Kokushikan University, Tokyo, Japan 2 Nippon Sport Science University, Tokyo, Japan 3 Tokushima Bunri University, Sanuki, Japan 4 Japanese Red Cross Hokkaido College of Nursing, Kitami, Japan 5 Ritsumeikan University, Kusatsu, Japan 6 Niigata University of Health and Welfare, Niigata, Japan The purpose of this study was to analyze the underwater gliding motion in collegiate competitive swimmers. Twelve male collegiate swimmers were monitored with a video camera (SK-2130, SONY, Japan) with a sampling frequency of 60Hz in the sagittal plane to measure the angular displacement of their different joints. A motion analysis system (Frame-DIAS4, DKH, Japan) was used to digitize ten body landmarks. The following results were obtained: the highest speed was maintained during the gliding motion when the knee and the hip joint angles of 180 degrees were maintained from push off from the wall to 0.8sec (1.82m). In addition, swimming speed slowed down when the involuntary movements of flexion-extension in the knee and the hip joints were observed during the gliding motion. Key words: Motion analysis, underwater gliding motion, competitive swimming IntroductIon In competitive swimming races, the improvement of swimming performance is related not only to the effect of stroking but also to performance of the start and the turn phase. Furthermore, it is important that the momentum created by a swimmer in the forward swimming direction is larger than in the opposite direction. Passive drag is produced by measuring the force necessary to tow a swimmer through the water at a constant speed with his body in a prone position (Adrian and Cooper 1995). The underwater gliding motion during the start and turn phases are important for the total race time in modern swimming (Marinho et al. 2009). Recently, the development of the swimsuit progressed rapidly. Previous studies suggested that this new model swimsuit had an effect on the body compression and the good streamlined posture (Chatard and Wilson 2008, Mollendorf et al. 2004, Roberts et al. 2003), and could reduce the passive drag during the underwater gliding motion (Chatard and Wilson 2008, Mollendorf et al. 2004). Furthermore, many companies have been developed new product of fabrics. These swimsuits were called “high speed” swimsuits. However, most research done by these companies, focusing on the effects of new fabrics, is not published. The “high speed” swimsuit were hypothesized to assist maintaining the knee and hip joint angles of 180 degrees, consequently, swimmers could keep a better body position and higher speed during the underwater gliding motion. The purpose of this study was to analyze the underwater gliding motion in collegiate competitive swimmers and to investigate whether wearing “high speed” swimsuit could maintain the knee and the hip joint angles of 180 degree. Methods Subjects and experimental procedures: Twelve healthy male collegiate swimmers (age 19.4±1.3yrs, height 170.0±5.0cm, body weight 67.0±4.8kg, BMI 23.2±1.5) volunteered to participate in this study. The chaPter2.Biomechanics subjects performed underwater gliding motion as fast as possible after a pushoff from the pool wall. During the underwater phase of gliding motion, the swimmer maintained streamline position (Elipot et al. 2009), and it was directed not to kick it. The head of the subjects were completely submerged during gliding. For each subject, only the fastest gliding motion was analyzed. The subjects were monitored with an underwater video camera (SK- 2130, SONY, Japan, Figure 1) with a sampling frequency of 60Hz in the sagittal plane to measure the angular displacement of their different joints. The underwater area covered by the camera ranged from the start wall to the 5-meter point. Figure 1. The underwater video camera (SK-2130, SONY, Japan) In this study, the subjects were asked to wear two different models of swimsuits: one is made of the conventional fabrics; the other is a newly developed, so-called “high speed” swimsuit (Figure 2 and 3, respectively). All subjects received a written and verbal explanation of the study and gave their written informed consent for participation. Approval was granted from the institutional human ethics committee and the study was conducted in conformity with the Declaration of Helsinki for medical research involving human subjects. Figure 2. A conventional fabric swimsuit. The “high-speed” swimsuit: The Speedo Fastskin LZR racer (LZR) is a fully bonded swimsuit (Figure 3). Its full-length bonded seams are ultrasonically welded together to eliminate stitching, creating the most low profile silhouette and reducing skin friction drag. The LZR is made from Speedo’s own LZR Pulse material the world’s lightest woven swimsuit fabric. It is highly compressive, water repellent, chlorine resistant and fast drying. The LZR is equipped with original panels of ultra-thin polyurethane membrane, precisely cut by laser, which are embedded into the base LZR Pulse fabric. The LZR Pulse fabric was strategically placed on important parts of the body to create a Hydro Form Compression system that provides an optimum streamlined shape and drag reduction for the swimmer. This system also provides a core stabilizer built to support and hold the athlete (Speedo International Limited 2009). However, these objective data were not published. 185
BiomechanicsandmedicineinswimmingXi Figure 3. The Speedo Fastskin LZR racer (LZR) swimsuits. Digitizing and data analysis: A motion analysis system (Frame-DIAS4, DKH, Japan) was used to digitize ten body landmarks. The ten anatomical landmarks chosen and identified are as follows: finger tips, head, tragus (ear), acromions, elbow, wrist, large trochanter, knee(femoral condyles), lateral malleolus, toes. The angular displacement of the joints are defined as internal joint angles (Figure 4). 186 Elbow joint angle Shoulder joint angle Hip joint anlge Knee joint angle Figure 4. The definition of the joint angular displacement. Ankle joint angle results Figure 5 indicates the stick picture of a swimmer obtained by means of the motion analysis system. The swimming speed of the subject’s center of gravity wearing a conventional swimsuit decreased when the flexionextension movement in the knee and the hip joints were performed during underwater gliding motion (a typical example is shown in Figure 6). On the other hand, the swimming velocity of those wearing an LZR swimsuit showed that the highest speed was maintained during the gliding motion when the knee and the hip joint angles of 180 degrees were maintained from the push-off from the wall to 0.8sec (1.82m) (a typical example is shown in Figure 7). The high-speed swimsuit maintained a streamline in a knee joint and a hip joint of 180 degrees in longer time (Table 1). In addition, duration of the swimming speed of the 90% equivalency of the best swimming speed was significantly longer wearing high-speed swimsuit (Table 2). Figure 5. The stick picture of the swimmer. Angular displacement (degree) 200 190 180 170 160 150 Subj.GY (Normal swimsuit) 0 0.2 0.4 0.6 0.8 1 Time (sec) Hip joint Knee joint Velocity of CG Figure 6. Relationship between the joint angle and the velocity for the normal swimsuit. This figure indicates that the knee and hip joints were performed flexion-extension movement from start to 0.8sec (1.2m). Angular displacement (degree) 200 190 180 170 160 150 Subj.GY (High-speed swimsuit) 0 0.2 0.4 0.6 0.8 1 Time (sec) 3 2.5 2 1.5 1 0.5 3 2.5 2 1.5 1 0.5 Hip joint Knee joint Velocity of CG Figure 7. Relationship between the joint angle and the velocity for the LZR swimsuit. This figure indicates that the knee and hip joints angle Biomechanics and Medicine in Swimming XI Chapter 2 Biomechanics b were fixed about 180 degree from start to 0.8sec (1.2m). 184 Table Biomechanics 1. The and comparison Medicine in Swimming high-speed XI swimsuit Chapter and 2 Biomechanics normal swimsuit b 184 in Table angular 1. displacement. The comparison (n=12) high-speed swimsuit and normal swimsuit in angular displacement. (n=12) Normal High-speed Table 1. The comparison high-speed swimsuit and swimsuit normal swimsuit in angular displacement. (n=12) Ave SD Ave SD Maximum hip joint angle(degree) 190.6 Normal 5.7 swimsuit 186.0 High-speed 4.3 swimsuit p
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Figure 1. General biomechanical par
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Figure 2. Repeatability of the LTin
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Pahlen Norge AS Pahlen Norge AS Cha
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