Differences in body composition and physical fitness of Korean national bobsleigh and skeleton athletes.

BACKGROUND: The aim of this study was to classify Olympic medalists and non-medalists among national bobsled and skeleton athletes and determine the physical fitness differences between the two groups. METHODS: Five bobsleigh and skeleton athletes who won gold and silver medals in the 2018 Pyeongchang Winter Olympics and 11 national bobsled and skeleton team athletes were recruited. The participants were assessed for physiological parameters such as body composition, anthropometry, physical fitness, isokinetic strength, and maximum strength. RESULTS: Physical fitness factors back strength (t=2.571, P<0.05), squat ability (t=3.061, P<0.01), and left and right leg curls (t=4.578, P<0.001; t=4.719, P<0.001, respectively) were significantly different between the groups. The original value of the primary discriminant analysis was 1.868 and the canonical correlation was 0.807. The average value of the discriminant function of the medalists was 1.896, while the of the non-medalists was -0.862, indicating that the two groups were completely different. CONCLUSIONS: Medalists have higher squat abilities, abdominal strength, and leg curl strength than non-medalists, particular regarding hamstring strength. Currently, in most sports events, athletes undergo physical training to improve performance; however, training programs that reflect the characteristics of the sport and the physical characteristics of excellent athletes are still insufficient.

The effect of whole body vibration on the sprint ability of Korean national bobsled and skeleton athletes.

This study aims to find out whether whole body vibration has an effect on the sprint ability to shorten the time of bobsled-skeleton athletes. Seventeen bobsled-skeleton athletes (male = 11, female = 6) were recruited from Korea Winter Olympics National Team. Participants were randomly assigned to either a sprint immediately after whole body vibration or a sprint without whole body vibration protocol during two separate visits by a period of 3 months. To evaluate the effects of the sprint ability, measurements were performed 60-m sprint recorded test. In males, at the 45m (p<0.05) significant faster sprint section record after WBV more than Non-WBV. In females, at the 15m (p<0.05), 30m (p<0.01), 45m (p<0.05), and 60m (p<0.05) significant faster sprint section record after WBV more than Non-WBV. In males, at the 30m (p<0.05), 45m (p<0.05), and 50m (p<0.05) significant faster sprint cumulative record after WBV more than Non-WBV. In females, at the 15m (p<0.05), 30m (p<0.05), 45m (p<0.01), 50m (p<0.01), and 60m (p<0.01) significant faster sprint cumulative record after WBV more than Non-WBV. This study indicated that significant faster after WBV more than Non-WBV in males and females bobsled-skeleton athletes.

Effects of Deposition Strategy and Preheating Temperature on Thermo-Mechanical Characteristics of Inconel 718 Super-Alloy Deposited on AISI 1045 Substrate Using a DED Process.

Thermomechanical characteristics are highly dependent on the deposition strategy of the directed energy deposition (DED) process, including the deposition path, the interpass time, the deposition volume, etc., as well as the preheating condition of the substrate. This paper aims to investigate the effects of the deposition strategy and the preheating temperature on thermomechanical characteristics of Inconel 718 super-alloy deposited on an AISI 1045 substrate using a DED process via finite element analyses (FEAs). FE models for different deposition strategies and preheating temperatures are created to examine the thermomechanical behavior. Sixteen deposition strategies are adopted to perform FEAs. The heat sink coefficient is estimated from a comparison of temperature histories of experiments and those of FEAs to obtain appropriate FE models. The influence of deposition strategies on residual stress distributions in the designed model for a small volume deposition is examined to determine feasible deposition strategies. In addition, the effects of the deposition strategy and the preheating temperature on residual stress distributions of the designed part for large volume deposition are investigated to predict a suitable deposition strategy of the DED head and appropriate preheating temperature of the substrate.

Purification and characterization of recombinant human endothelin receptor type A.

Human endothelin receptor type A (ET(A)) is a G-protein coupled receptor that mediates vasoconstriction of blood vessels. To determine the structural characteristics and signaling mechanism of ET(A), we have expressed recombinant ET(A) as a fusion protein with p9 envelope protein from phi6 bacteriophage. The His-tag-labeled p9-ET(A) fusion protein was highly expressed in the membrane fraction of Escherichia coli and purified to homogeneity by single affinity chromatography after solubilization with detergents. Purified p9-ET(A) appeared as an oligomer and presented mainly as an α-helical structure. The protein also showed specific binding to endothelin-1 (ET-1) and the alpha subunit of G(q) protein with apparent K(D) values of 17 and 20 nM, respectively. An antagonist of ET(A), bosentan, prevented the interaction between p9-ET(A) and ET-1 in a concentration-dependent manner. These results indicate that recombinant p9-ET(A) has a competent conformation for interactions with ET-1 and the alpha subunit of G(q) protein.