Relationship between boat velocity and stroke parameters in the men's junior canoe single 200m race

This study aimed to assess boat velocity and stroke parameters in the men’s junior canoe single 200m race, focusing mainly on identifying which stroke parameters are most closely linked to boat velocity. Our analysis included forty junior male canoe paddlers, with race times ranging from 42.799 to 54.231 seconds. We measured boat velocity, stroke frequency (SR), and distance per stroke (DPS) across three race phases: the initial (0−25 m), middle (100−125 m), and final (175−200 m), using video footage. The findings reveal that SR and DPS significantly correlate with boat velocity. However, SR appears to have a more substantial influence on boat velocity. This emphasizes the need for coaches and paddlers to closely monitor and adjust SR and DPS during training to optimize performance

Estimations of body segment parameters in Japanese adult females using MRI methods

This study aimed to estimate of Body segment parameters （BSPs） in Japanese adult females using magnetic resonance imaging （MRI） methods. Whole-body MR date of 14 Japanese adult females were obtained using 1.5-T MRI scanner. Thirteen tissue areas were identified by MR dates using Fiji/ImageJ software. Body composition and Limb composition were calculated by multiplying each area,10-mm slice thickness and identified tissue densities. Fourteen body segments such as head and neck, trunk, upper arm, forearm, hand, thigh, shank and foot were defined according to the anatomical landmarks in MR dates. Segment mases （%body mass; %BW） and center of masses （%segment length; %SL） obtained from MRI were compared with regression modeling from previous studies. 　The results of this study have trended to be smaller in upper arm and forearm than typical values. Females were bigger thigh and shank than males, indicating sex difference affected segment mass. Center of masses （CMs） were affected by the definition of segment lengths. It suggested females accumulated fat mass close to trunk. The CM of trunk in female was lower than previous studies, because upper trunk had lower muscle mass than male. These results suggest to consider the influence of female-specific body segment components

Characteristics of the Take-off phase of the Top Japanese men's pole vaulter

This study aims to clarify kinematic and kinetic characteristics during the Takeoff Phase, for Japanese pole vaulters including top-class Japanese athletes. This study was conducted with seven male pole vaulters (PB：5.46±0.23 m, height：178±4.7 cm, weight：70±5.2 kg). The trials were captured using a three-dimensional motion analysis system (VICON) to acquire three-dimensional kinematic data. Ground reaction forces (GRF) during the Take-off Phase were recorded using a force plate (KISTLER) situated underneath the runway and box. Subject A considered as the top performer, exhibiting the greatest propulsive GRF (0.5 N/BW) compared to other subjects . Subject A demonstrated a propensity to have a higher horizontal velocity of COM at TO, with PP appearing later in the contact phase, consistent with previous research. It was suggested that the pole began to bend at the point where the maximum propulsive force GRF of the supporting limb occurred, thereby acquiring a larger horizontal box reaction force and a larger horizontal velocity COM at takeoff

Comparison of Kinematics and Kinetics in Elite Rowers Using a Slide Rowing Ergometer

Rowing ergometers are widely used in land-based training for various types of athletes. The relationship between athletic performance, mechanical power, physiological indicators, and other factors has been discussed about the fixed-type rowing ergometer. However, it has been pointed out that the movement and sensation of the athlete differed from the actual rowing motion on water. To address this issue, a slide-type rowing ergometer has been devised, where the ergometer is placed on rails, allowing both the seat and the ergometer to slide. However, there is limited prior research on the slide-type rowing ergometer, and many aspects regarding its usefulness remain unclear. This study aimed to characterize junior and senior rowers using a sliding ergometer. A custom-made Air pressure resistance type rowing ergometer (Concept II model c indoor Rower) was used for this study. The sliding-type rowing ergometer was mounted on two ergometer slides (manufactured by Concept II). The subjects were 12 high school and college rowers who performed a 2000 m simulation using a sliding rowing ergometer. Rowing motion was filmed by a high speed video camera (200fps) from right angles beside the subject. Hip and knee joint angles were measured as 180 degrees of full extension. The subject placed their foot on each foot plate (VINE, 200Hz). Spatiotemporal parameters of the handle, mechanical output from the handle and stretcher, and angular displacements and angular velocities of the ankle, knee, and hip were calculated. Senior rowers had shorter drive phases and longer recovery phases. Senior rowers also had higher handle and stretcher forces. Senior rowers are suggested to utilize different techniques than juniors during rowing due to higher leg and handle strength and different drive and recovery times

Changes in medial longitudinal arch and plantar load during walking at different speeds

The purpose of this study was to clarify the changes in the medial longitudinal arch (MLA) and plantar load distribution during the stance phase of walking at different speeds. Eight healthy male subjects participated in this study. Plantar pressure measurement plate (Novel GmbH®, 100Hz), motion capture system (Oxford, 100Hz) and force plate (Kistler, 1KHz) were synchronized. Using this system, subjects performed 3 walking trial at 0.8 (Slow), 1.2 (Normal), 1.7 (Fast) m/s. Plantar load distribution was divided into five sub-area based on anatomical measurement points. MLA angle was calculated as the angle between the distal first metatarsal, navicular tuberosity and calcaneus. In comparison with Slow, Fast showed no difference in the amount of change in MLA angle, despite the greater load applied to the medial forefoot at push-off phase. Increasing the plantar loads in medial foot as well as stiffening the MLA might be important roles during push-off phase in walking at fast speed

Effects of exposing to periodic hypobaric normoxia environment on physiological parameters and swimming performance

The purpose of this study was to (1) determine the effects of staying in PHNC during the recovery period after supramaximal exercise on oxygen uptake (VO₂), HR and blood lactate (La). (2) To determine the effect of PHNE intervention on performance and skin temperature in the post-training period. Experiment (1) : Seven healthy male athletes (23±5 yrs, 173±6 cm, 79±15 kg) participated in this study. All tests were conducted by an electromagnetically braked cycle ergometer, and PHNE was an environment that repeats cycles of decompression (Atmospheric pressure : approximately 670mmHg) in 3 minutes and abdominal pressure (Atmospheric pressure : approximately 730mmHg) in 3 minutes. At first, subjects had been measured the maximal oxygen uptake (VO₂max). Secondly, supramaximal constant exercise are performed at 115%VO₂max of 1min, and the rest after two different conditions of 60min recovery (NN vs. PHNE). Experiment (2) : Ten male and female competitive swimmers were included in the study (PHNE group : 5, CON group : 5). Both groups had the same training menu, and the PHNE group was exposed to PHNE at rest for 1 hour after the end of training. Surface skin temperature was also measured and recorded before and after the intervention for the PHNE group. Performance was based on 8 target matches that were between December 2016 and May 2017. The results of each match were calculated as a percentage of their personal best through November 2016 (performance index). During the exercise, there was no significantly difference in VO₂ in two conditions. VE, HR and La no differences in two conditions during recovery period. On the other hand in PHNE condition, VO₂ and a time constant were higher, and VE/VO₂ and R were lower compared to NN condition. Improvement of ventilation efficiency and promotion of a fat metabolism might be suggested by staying at PHNE. PHNE exposure had no influence on blood lactic acid accumulations. Hyperfunctions of VO₂ and fat metabolism might be suggested by exposuring PHNE during recovery period after one minute supramaximal exercise bout. It is also possible that PHNE intervention between training sessions may promote recovery and consistent performance

Biomechanics study on Penche rotation in Japanese elite female rhythmic gymnast

This study aimed to compare the angular momentum during Penche rotations in skilled and unskilled rhythmic gymnastics. Eleven collegiate female rhythmic gymnasts participated in this study. The experimental trial consisted of Penche rotations intended to turn many number of rotations as possible. The skilled group (n＝6) consisted of athletes who could perform 2 to 3 rotations, and the unskilled group (n＝5) consisted of athletes who performed one rotation or less. Kinematics data were collected using a motion capture system to calculate angular momentum around the body’s center of gravity and the z-axis for each segment. The skilled group that performed two to three Penche rotation rotations had significantly greater angular momentum around the body center of gravity, head, trunk, pelvis, left upper extremity, and free leg than the unskilled group. The maximum angular momentum of the right upper limb in the preparatory phase was significantly greater in the skilled group than in the unskilled group. These results suggest that the movements of the left and right upper limbs and the free leg in the preparatory phase are important to increase the number of Penche rotations

Reaction times of punching movements in female collegiate karate athletes based on ground reaction forces and kinematics : Focus on kumite international level athlete

The purpose of this study was to clarify the reaction times of karate athletes against opponents based on kinetics and kinematics in karate kumite. In addition, the reaction times of international, university and kata athletes are compared to examine the characteristics of international-level athletes. Thirteen female university karate athletes (kumite international level：n＝2, kumite university level：n＝6, kata：n＝5) participated in this study. Fourteen motion capture cameras and three force plates were used to record kizami-tsuki and gyaku-thuki movements to LED light stimuli and the opponent’s movement. Kinetics and kinematics analysis showed no differences in reaction times od LED light stimuli between kumite, kata and competition levels. But international level kumite athletes tended to have the shorter reaction times against opponent’s movement. In conclusion, these results suggest that kumite international level athletes have an excellent ability to predict and estimate the movements of their opponents