Underwater Dolphin Kick Research Articles

Underwater flutter kicking causes deceleration in start and turn segments of front crawl

ABSTRACTThis study investigated the deceleration effect of flutter kicking after dolphin kicking before commencing the stroke at swimmer’s emersion. Eight male competitive swimmers (age 19.6 ± 1.2 years; Fédération Internationale de Natation points 733.6 ± 57.5) performed 15 m front crawl sprints from wall push-off three times in a row, with two types of underwater kicks [dolphin kick only (dolphin condition) and dolphin kick followed by flutter kick (dolphin-flutter condition)]. Sprint bouts were divided into four phases. Phases 1 and 2 were defined, respectively, as the fourth and fifth dolphin kicks. Phase 3 was defined as the first stroke (dolphin condition) and six beats of the flutter kicking (dolphin-flutter condition). Phase 4 was defined as the second stroke (dolphin condition) and the first stroke (dolphin-flutter condition). Two-way repeated measured analysis of variance on mean swimming velocities demonstrated an interaction of condition and phase (p < 0.001) and a simple main effect (p < 0.001) at Phase 3. These results indicated greater deceleration due to adding the flutter kick after the dolphin kick before commencing the stroke. Swimmers should use only the underwater dolphin kick before commencing the front crawl in start and turn segments.

The sound of the underwater dolphin-kick: developing real-time audio feedback in swimming

One of the main factors for improving movement execution and motor performance in competitive sports is the availability of useful feedback. While coaches can communicate verbally with athletes in most sports, swimming is different. Because the swimmer is underwater most of the time, any type of real-time feedback is difficult. Since the presentation of acoustic information through sonification has proven beneficial to certain motor skills, this paper describes initial considerations for an application of interactive sonification as real-time audio feedback to provide useful information to improve motor execution in swimming. Special attention is given to the underwater dolphin-kick (UDK), which is performed by athletes after every start and every turn and is one of the critical factors for overall performance in world-class swimming. It was examined whether the characteristics of the UDK are represented in the sound in order to create congruency between sound, action and reaction.Two different sonification models were designed using data from 11 national athletes (six juniors, aged 17.0 ± 1.5 years and five seniors aged 23.6 ± 1.3 years). The sonified data were presented to sport scientists and coaches and tested in in a pilot study with three club-level swimmers (17.0 ± 0.8 years) in swimming training. The results indicate that the athletes became aware of relevant aspects of the movement with both sonification models, to which they had no access so far. In detail, the sonification provided information on forward propulsion, movement rhythm and kick frequency – all factors contributing to overall motor performance. Individual statements showed that the athletes noticed deceleration phases in the forward propulsion and the time duration in the movement execution and tried to adapt their movements accordingly. The approaches presented here could therefore serve as a useful training tool for swimmers to improve their UDK.

Effect of increased kick frequency on propelling efficiency and muscular co-activation during underwater dolphin kick

In this study, we investigated the effects of increased kick frequency on the propelling efficiency and the muscular co-activation during underwater dolphin kick. Participants included eight female collegiate swimmers. The participants performed seven 15-m underwater dolphin kick swimming trials at different kick frequencies, which is 85, 90, 95, 100, 105, 110, and 115% of their maximum effort. The Froude (propelling) efficiency of the dolphin kick was calculated from the kinematic analysis. The surface electromyography was measured from six muscles (rectus abdominis, erector spinae, rectus femoris, biceps femoris, tibialis anterior, and gastrocnemius). From the EMG data, the co-active phase during one cycle in the trunk, thigh, and leg was evaluated. Our results show that the Froude efficiency decreased at the supra-maximum kick frequency (e.g. 100%F: 0.72±0.03 vs. 115%F: 0.70±0.03, p<.05). The co-active phase in the trunk, thigh, and leg increased with increasing the kick frequency (e.g. 85%F vs. 115%F, p<0.05). Furthermore, it was observed that there was a negative relationship between the trunk co-active phase and the Froude efficiency (r=−0.527, p<0.05). Therefore, both the propelling efficiency and the muscular activation pattern became inefficient when the swimmer increased their kick frequency above their maximum effort.

The Relationship Between Dolphin Kick Movement And Underwater EMG Of Lower Leg Muscles In Competitive Swimmers

Improvement in swimming performance is not only associated with stroke technique but also with the gliding movement during the start and turn phases. The underwater dolphin kick movement during the start and turn phases is important for improving total race time in modern swimming. PURPOSE: The study was designed to analyze the findings of underwater electromyography of lower limb muscles during the underwater dolphin kick movement in competitive collegiate swimmers. METHODS: Six healthy male collegiate swimmers volunteered to participate in this study. The subjects performed underwater gliding movement at maximum speed after pushing off from the start wall. In addition, three types of underwater dolphin kick movement [Control (C): maximum effort kick; Build-up (BU): small-to-large kick; and Dynamic (D): large kick) were performed with maximum effort. The subjects were monitored through an underwater video camera with a sampling frequency of 60 Hz in the sagittal plane to measure the angular displacement of their different joints. A wireless electromyography system (Biolog DL-5000, S&ME, Japan) was used to collect the muscle activities from the vastus lateralis, hamstrings, tibialis anterior, and gastrocnemius. Speed Meter (Vine Co., Japan) was used to measure swimming speed, and a motion analysis system (Frame-DIAS4; DKH, Japan) was used to digitize body landmarks. RESULTS: Among the underwater dolphin kick movement types, the BU kick was the fastest (BU: 1.67 m/s; C: 1.65 m/s; and D: 1.65 m/s). The rectified EMG findings showed that gastrocnemius and hamstrings muscle activities of elite swimmers were higher than non-elite swimmers during these movements. However, elite swimmers had no muscle activity in the tibialis anterior. CONCLUSIONS: The present study results suggested that the angular displacement of the knee joints gradually increases during underwater dolphin kick movement. In addition, the muscle activity of the hamstrings and gastrocnemius increase during underwater dolphin kick movement. However, the muscle activity of tibialis anterior was inhibited during these movements. Our results also suggested that swimmers experienced a large propulsion force and a small resistance force with the help of these movements.

エリート女性競泳選手の水中ドルフィンキックにおける体幹，大腿，下腿の筋活動様式

エリート女性競泳選手の水中ドルフィンキックにおける体幹，大腿，下腿の筋活動様式

Importance of sagittal kick symmetry for underwater dolphin kick performance

The purpose of this study was to determine how sagittal kick symmetry in the underwater dolphin kick (UDK) between the downkick and upkick phases is related to UDK performance. Fifteen adult male competitive swimmers ranging from provincial to international level were filmed performing three trials each of maximum effort UDK over 15m using an underwater video camera. Video frames were manually digitized and each subjects’ single fastest trial was evaluated for between-subject comparisons. Kinematic variables were calculated for each individual and Pearson product-moment correlations between the average horizontal centre of mass velocity (Vx) and all kinematic variables were calculated. Horizontal velocity during the downkick, horizontal velocity during the upkick, relative time spent in each phase, maximum chest flexion angle, maximum knee and ankle extension angles, the ratio of flexion/extension for chest, knee and ankle angles, and maximum vertical toe velocity during the upkick phase correlated significantly with Vx (p<0.05). The ratio of downkick vertical toe velocity/upkick vertical toe velocity was significantly negatively correlated with Vx (p<0.05). These results indicate the importance of kick symmetry for UDK performance, and indicate that performing the upkick phase well appears to be most important for UDK performance.

Pelvis-Upper Trunk Coordination at Butterfly Stroke and Underwater Dolphin Kick: Application on an Elite Female Butterfly Swimmer

Pelvis-Upper Trunk Coordination at Butterfly Stroke and Underwater Dolphin Kick: Application on an Elite Female Butterfly Swimmer Swimming strokes kinematics are traditionally monitored, analyzed and extracted for a small part of a race. This practice may facilitate methodological limitations due to restricting issues arising from video analysis, though it is not scientifically solid, despite the cyclic nature of swimming movements, which may justify it. Skill level, swimming speed and fatigue are just some of the factors or constraints that may interfere with the cyclic nature of swimming and therefore affect inter-segmental coordination from stroke to stroke. There are studies that describe inter-segmental coordination in swimming using up to four consecutive stroke cycles. Nevertheless, studyinG coordination especially under the perspective of dynamic systems theory demands a large number of strokes to be analyzed in order to bring out the underlying coordination pattern, accounting also for its stability over time.

An Analysis Of The Underwater Gliding Motion And Dolphin Kick In The Competitive Swimming

An Analysis Of The Underwater Gliding Motion And Dolphin Kick In The Competitive Swimming

코어 안정화 운동과 서킷 웨이트 트레이닝이 신체구성, 유연성, 근력, 근지구력 및 수중 돌핀킥 기록에 미치는 영향

The objective of the research was to analyze the change of the record of the dolphin kick as well as the body composition and healthy fitness and to compare the effect of the different type of exercise programs; circuit weight training and core stability exercise. We divided into two groups of eleven people; one group was trained with complex programs of core stability exercise(CSE, n=11), the other was with circuit weight training(CWT, n=11) programs three times a week for 12 weeks for 100 minutes each session. Experimental data were analysed by SPSS 12.0 using two-way ANOVA with repeated measure. WHR and %FAT of body composition significantly decreased in two groups of exercising program(p<0.05). Weight significantly decreased only in core stability exercise group(p<0.05). The flexibility significantly increased only in core stability exercise group(p<0.05). The lumbar strength and lumbar strength ratio significantly increased only in circuit weight training group(p<0.05), but lumbar endurance strength significantly increased in two groups together(p<0.05). The record of the underwater dolphin kick significantly improved in two groups(p<0.05). According to the results both groups showed the positive effects in every measurement parameters. Therefore, it could be concluded that both of the exercise programs are suggested as the effective complex programs to every swimmer including amateur who has a goal to shorten their record of the underwater dolphin kick.

Propulsive Efficiency of the Underwater Dolphin Kick in Humans

Three-dimensional fully unsteady computational fluid dynamic simulations of five Olympic-level swimmers performing the underwater dolphin kick are used to estimate the swimmer's propulsive efficiencies. These estimates are compared with those of a cetacean performing the dolphin kick. The geometries of the swimmers and the cetacean are based on laser and CT scans, respectively, and the stroke kinematics is based on underwater video footage. The simulations indicate that the propulsive efficiency for human swimmers varies over a relatively wide range from about 11% to 29%. The efficiency of the cetacean is found to be about 56%, which is significantly higher than the human swimmers. The computed efficiency is found not to correlate with either the slender body theory or with the Strouhal number.

A computational method for analysis of underwater dolphin kick hydrodynamics in human swimming

We present a new method that combines the use of laser body scans, underwater video footage, software-based animation, and a fully unsteady computational fluid dynamics technique to simulate and examine the hydrodynamics of the dolphin kick. The focus of the current work is to model this particular stroke in all its complexity with minimal ad-hoc assumptions or simplifications. Simulations of one female and one male swimmer (both at about 1.7 m beneath the water surface) at velocities of 0.95 and 1.31 m/s and Strouhal numbers of 1.21 and 1.06 respectively are presented. Vorticity and fluid velocity profiles in the wake are examined in detail for both swimmers. A three-dimensional vortex ring is clearly identified in the wake for one of the cases and a two-dimensional slice through the ring corroborates previous experiments of Miwa et al. (2006). We also find that most of the thrust is produced by the feet and in both cases the down-kick produces much larger thrust than the up-kick.

Simulation Analysis of the Effect of Trunk Undulation on Swimming Performance in Underwater Dolphin Kick of Human

The objectives of this study were to investigate the effect of trunk undulation on the swimming performance in underwater dolphin kick, and to clarify the ideal trunk undulation form. The reference swimming motion of an elite swimmer was firstly acquired from the video analysis, and input into the swimming human simulation model SWUM, which had been developed by the authors. The trunk motion was next optimized by the simulation for three objective functions: maximizing swimming speed, maximizing propulsive efficiency, and minimizing fluid force acting on hands. The following findings were obtained: In the case of maximizing swimming speed, the whole body forms a ‘C’ shape due to the in-phase trunk undulation. The swimming motion of maximizing propulsive efficiency and the reference swimming are considerably similar to each other. In both cases, the trunk moves as a seesaw with a node; whereas, the lower limbs form a traveling wave in the absolute space. The values of propulsive efficiency are around 0.2 in the cases of maximizing propulsive efficiency, minimizing fluid force on hands, and the reference swimming. The swimming motion in the case of minimizing fluid force on hands is almost the same as that of maximizing propulsive efficiency. The trunk undulation with the appropriate amplitudes and phases, especially bending at the chest, is important in realizing the swimming motion which maximizes propulsive efficiency.

シミュレーション解析による水中ドルフィンキック時の足関節底屈角度の増加がパフォーマンスに与える影響

The purpose of this study was to investigate the relationship between plantar flexion angle and underwater dolphin kick performance using a simulation model, SWUM (SWimming hUman Model), in which the entire body was represented as a series of elliptic cylinders. Three unsteady fluid forces (added mass force, normal and tangential resistive force), buoyancy and gravity acting on the elliptic cylinders were computed from the shape and density of the cylinders, and from the joint motion for one cycle. Eight elite competitive swimmers participated in this study. Their body characteristics were measured and input as the simulation data (the shape and density of the elliptic cylinders). The joint motion data for one cycle were obtained by the 2-D DLT method during the underwater dolphin kick. To recreate the dynamics of the underwater dolphin kick in the simulation, three fluid coefficients, used to calculate the three unsteady fluid forces, were identified to minimize the difference between measured and simulated swimming velocity by the least-squares method. This identification was conducted for each of the input data. Simulations of the increased plantar flexion angle in the knee extension phase were executed with the optimal fluid coefficients for each swimmer in order to analyze the change in swimming velocity and thrust generated by the feet. The conclusions can be summarized as follows : (1) Swimming velocity during the underwater dolphin kick increased due to the increment of the thrust generated by the feet after an increase in the plantar flexion angle. (2) It was suggested that flexibility of plantar flexion is important, although it is not a determinant of underwater dolphin kick performance. (3) Swimmers with low flexibility of plantar flexion tended to achieve a faster swimming velocity after increasing the plantar flexion angle.

A39 水中ドルフィンキックにおける体幹のうねりがパフォーマンスに及ぼす影響のシミュレーション解析(ウォータースポーツ)

A39 水中ドルフィンキックにおける体幹のうねりがパフォーマンスに及ぼす影響のシミュレーション解析(ウォータースポーツ)

ドルフィンキック動作と立位体幹屈伸動作における腰椎，骨盤および股関節の連動の比較

Low-back pain is one of the most common injuries in competitive swimmers. Therefore, the prevention of low-back pain would contribute to improved performance of swimmers. A biomechanical analysis is necessary to prevent the sports-related injuries. However, only lumbar movement has been analyzed in swimmers with low-back pain. Lumbar spine movement is closely associated with the pelvis and hip joint. Thus, not only the lumbar joint but also the pelvis and hip joint should be analyzed to determine the cause of low-back pain.The aim of this study was to investigate the relationship of the effect of underwater movement on the motion characteristics of the lumbar, lumbosacral, and hip joints with trunk flexion-extension in the standing position.Fourteen male competitive swimmers were recruited for this study. Trunk flexion-extension motion in the standing position and underwater dolphin kick motion were captured in the saggital plane on a digital video camera. A 2D motion analysis was performed to determine the lumbar, lumbosacral, and hip joint angles during these motions.The results demonstrated that the lumbar angle during the dolphin kick motion was associated with the angle in the standing position when the trunk was extended; and the lumbosacral angle during the same motion was associated with the angle in the standing position when the trunk was flexed.Additionally, the subjects who tilted their pelvis anteriorly while swimming exhibited a bit of pelvis motion during trunk movement in the standing position. Thus, the anterior tilting of the pelvis during swimming leads to low-back pain in swimmers.

A40 シミュレーション解析による足関節底屈角度増加が水中ドルフィンキックのパフォーマンスに与える影響(水泳)

A40 シミュレーション解析による足関節底屈角度増加が水中ドルフィンキックのパフォーマンスに与える影響(水泳)