ACTIVATION PATTERN OF TRUNK, THIGH AND LOWER LEG MUCLES DURING UNDERWATER DOLPHIN KICK IN SKILLED FEMALE SWIMMERS

This study investigated the muscle activation pattern between the agonist and the antagonist muscles in the trunk, thigh and lower leg during underwater dolphin kick. Thirteen female elite swimmers participated in this study and they performed 15 m underwater dolphin kick swimming at maximum effort. The surface electromyography (sEMG) of six muscles were measured and the muscle activation pattern between the agonist and antagonist muscles in the trunk, thigh and lower leg were estimated from the sEMG data. As results, the trunk and the thigh muscles showed a reciprocal activation pattern during one-kick cycle. However, the activation pattern of the lower leg muscles did not show a reciprocal pattern and it was clarified that the lower leg muscles were co-activated during the upward kick phase

A FLOW VISUALEATION OF UNDULATORY UNDERWATER SWIMMING -A PILOT STUDY OF THREE DEIMENTIONAL AMALYSIS

The purpose of this study was to visualize the flow characteristic behind a swimmer during undulatory underwater swimming (UUS). A male college swimmer performed dolphin kicks in a water flume channel (flow velocity was set at 0.8 m+sl). By using the stereo PIV system, we captured the flow vector field in cross-sectional areas behind the swimmer and the swimmer's motions with a synchronized motion capture system. The vector fields were averaged for each kicking phase, and for spatial cross-sectional plane. This enabled visualization oft he three dimensional flow field in UUS. The results showed that the swimmer created a counter vortex pair around the feet before the downward kid, and this appeared to assist the generation of thrust during the down kick motion

THREE-DIMENSIONAL FLOW FIELD AND LEG MOTION DURING UNDULATORY UNDERWATER SWIMMING

This study described swimmers’ leg motions and the three-dimensional flow field around their legs during undulatory underwater swimming (UUS). We used the particle image velocimetry (PIV) method and a three-dimensional motion capture system. Seven male swimmers participated and we acquired EMG data of one male swimmer during UUS after the previous experiment. After the downward kick motion that includes the legs’ lateral rotation and the ankles’ dorsal flexion, water’s backward momentum was observed. During the upward kick motion, backward flow velocity decreased, but flow occurred in a vertical, upward direction. This suggested that UUS could demonstrate great propulsion power by generating jet flow through the downward kick motion that might be assisted by upstream flow from the upward kick motion

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

 The purpose of this study was to clarify the pattern of muscular activity in the trunk, thigh and lower leg during the underwater dolphin kick in elite female competitive swimmers. The participants were 9 national-level competitive female swimmers who performed underwater dolphin kick swimming for 15 m at maximum effort. Sagittal movement was recorded for 2-D motion analysis, and surface electromyographic (EMG) data were recorded from 6 muscles: rectus abdominis (RA), elector spinae (ES), rectus femoris (RF), biceps femoris (BF), tibialis anterior (TA), and gastrocnemius (GAS). The EMG data were used to investigate the active phase during one kick cycle. Furthermore, the co-active phases between the agonist and the antagonist in the trunk, thigh and lower leg were evaluated in terms of estimated muscular coordination. The kinematic results indicated that the average swimming velocity and the strouhal number for these swimmers were similar to those for Olympic swimmers in a previous study. Furthermore, a whiplash-like action was observed in their underwater dolphin kick movement. The EMG results indicated that the active phases of all subjective muscles during one kick cycle were approximately 60%. Co-active phases were observed in all pairs (RA-ES: 24.1±10.1%, RF-BF: 23.2±5.5%, TA-GAS: 45.5±20.2%), and the co-active phase of TA-GAS was significantly larger than for the other pairs (p<0.05). From these results, two main findings emerged with regard to the muscular activity pattern during the underwater dolphin kick in elite female competitive swimmers: (1) the muscular activity patterns in the trunk and thigh muscles were reciprocal; (2) the co-active phase for the lower leg muscles was larger than for the other parts and occurred during the first half of the upward kick phase

多段階の泳速度におけるクロール泳中の自己推進時抵抗とストリームライン姿勢中の受動抵抗の比較

The purpose of this study was to compare active drag during front-crawl swimming performed by competitive swimmers with passive drag acting on the same group of swimmers with a streamlined position at various velocities. Seven male competitive swimmers participated in this study, and the testing was conducted in a swimming flume. Active drag was evaluated for front-crawl swimming with upper and lower limb motion using a methodology that estimates the drag in swimming using measured residual thrust values (MRT method). Passive drag was measured by a load cell connected to the swimmers with a streamlined position using a stainless-steel wire. In each case, drag was estimated at six staged velocities ranging from 1.0 to 1.5 m/s. To compare the drags at various velocities, we calculated coefficients a and b by applying the measured force value at each velocity to the equation D = a vb (D: drag, v: velocity). The active drag estimated from the MRT method (a = 35.7 ± 5.3, b = 2.80 ± 0.22) was larger than passive drag (a = 23.6 ± 3.1, b = 2.08 ± 0.23). Furthermore, the difference between active and passive drag was large at high velocities. Therefore, it is possible that the effects of factors other than posture and/or body shape have a large influence on active drag, especially at high velocity

A STUDY OF FLUID FORCES ACTING ON A FOOT DURING EGGBEATER KICKS OF WATER POLO PLAYERS

The purpose of this study was to estimate fluid forces acting on a foot during eggbeater kicks of water polo players by the pressure-distribution-measuring method. Six male water polo players performed eggbeater kicks. Four pairs of pressure sensors were attached to the dominant foot to measure pressure distribution. Fluid-force vectors were calculated. The eggbeater kick cycles were divided into three phases (i.e. out-, in- and upkick phase) based on the knee joint angle and the displacement of the ankle. Maximum values and mean values of the propulsive component of fluid forces were 165.4 * 24.6 N and 38.2 * 4.6 N (mean i SD). Moreover, it was established that a swimmer mainly produces propulsive forces during out-kick and in-kick phases

Kinematic and EMG data during underwater dolphin kick change while synchronizing with or without synchronization of kick frequency with the beat of a metronome

We investigated the effects of synchronizing kick frequency with the beat of a metronome on kinematic and electromyographic (EMG) parameters during the underwater dolphin kick as a pilot study related to the research that entitled “Effect of increased kick frequency on propelling efficiency and muscular co-activation during underwater dolphin kick” (Yamakawa et al., 2017) [1]. Seven collegiate female swimmers participated in this experiment. The participants conducted two underwater dolphin kick trials: swimming freely at maximum effort, and swimming while synchronizing the kick frequency of maximum effort with the beat of a metronome. The kinematic parameters during the underwater dolphin kick were calculated by 2-D motion analysis, and surface electromyographic measurements were taken from six muscles (rectus abdominis, erector spinae, rectus femoris, biceps femoris, tibialis anterior, and gastrocnemius). The results revealed no significant differences in the kinematic and EMG parameters between trials of the two swimming techniques. Therefore, the action of synchronizing the kick frequency with the beat of a metronome did not affect movement or muscle activity during the underwater dolphin kick in this experiment