A comparative study on the reliability and validity of body composition results by impedance method measurement device.

The purpose of this study was to analyze the reliability and validity of the body composition results for each impedance device and use them as primary data for body composition research. Total of 58 participants, including 24 men and 34 women, were recruited. The correlation was analyzed by measuring two repetitive measurements for each device. Dual energy x-ray absorptiometry (DEXA) equipment was used as reference equipment for body composition research. All data were analyzed as IBM SPSS Statistics ver. 25.0, and the validity and reliability were estimated by calculating the timely correlation coefficient. As a result of the study, repeated measurements of the measuring instrument showed high reliability by gender and age, especially in the child age group, with relatively higher reliability than those in their 50s or older. In the validity analysis between DEXA, in the case of the male group, the validity of the fat mass amount was relatively higher than the body fat amount and body fat rate. In the case of the women's group, the validity of the body fat amount and body fat rate was relatively higher than that of the fat mass amount. The company B had the highest validity for body fat rate and body fat amount in both men and women. However, the validity for men's fat mass amount was the lowest. In subsequent studies, it is believed that studies that have expanded the population further and studies targeting special groups such as athletes should be conducted.

Relative Contribution among Physical Fitness Factors Contributing to the Performance of Modern Pentathlon.

This study reveals the relationship between physical fitness factors and performance in modern pentathlon and identifies the contribution of each physical factor to overall performance. The physical fitness assessment data and the competition records collected by the Korean national team pentathletes for the years 2005 to 2019 were tracked. The correlation between the competition records and fitness factors was confirmed by correlation analysis. In addition, the physical factors affecting performance were identified through multiple regression analysis, and the average difference between national and international competitions was verified by t-test. The first result was that fencing, swimming, and horseback riding rankings were more relevant to the overall pentathlon performance score than the combined rankings in national competitions. In the international competitions, performance in the combined running and shooting event was more relevant than fencing, swimming, and horseback riding. Second, the basic fitness factors of grip strength and sergeant jump and the specific fitness factors of leg strength-left and right average flexor were correlated with overall pentathlon performance national competitions. However, in international competitions, sergeant jump, 20 m shuttle run, reaction time, lung capacity, and back strength were correlated (presented in high to low order). In terms of the specific fitness factors, relative (%BW) and absolute (Nm) leg strength-left and right average flexor, lower body anaerobic fatigue rate, half squat, relative (W/kg) and absolute (Watts) maximal lower body anaerobic power were correlated accordingly with overall pentathlon performance. Third, we analyzed the differences between average performance in national and international competitions. Only the combined running and shooting event out of the five modern pentathlon events showed a difference. Grip strength and relative leg strength-average extensor AP (%BW) appeared to be different among the physical fitness factors. Fourth, we examined the level of contribution of each of the fitness factors on overall performance. The model's goodness of fit was confirmed, and grip strength was found to have a significant contribution on overall performance. Furthermore, the level of contribution was higher in the following order: relative leg strength-left and right average flexor (%BW), bench press, half squat, relative leg strength-average extensor AP(%BW), GXT-time to exhaustion, relative lower body anaerobic average power (W/kg), and maximal lactic acid concentration. With the 2020 Tokyo Olympics just around the corner, combined running and shooting performance appeared to be a decisive factor in the final ranking in modern pentathlon according to the analysis of the basic and specific fitness factors of pentathletes. The basic fitness factors are critical in order of sergeant jump, grip strength, reaction time, lung capacity, side-step, back strength, 20m shuttle run, sit-and-reach, sit-ups, and single leg standing. With respect to the specific fitness factors, relative leg strength-left and right average flexor (%BW), bench press, half squat, relative leg strength-average extensor AP (%BW), GXT-time to exhaustion, relative lower body anaerobic average power (W/kg), and maximal lactic acid concentration showed their relevance accordingly.

The Relationship between Changes in GRIT, Taekwondo Ability, and Academic Achievement of University Students Majoring in Science and Engineering and Participating in Taekwondo Class.

GRIT, which was conceptualized by the American psychologist Duckworth, was designed by grouping growth (G), resilience (R), intrinsic motivation (I), and tenacity (T), which means continuing to be patient and put in effort to achieve goals without being frustrated by adversity or failures experienced in the process of striving toward one's goals. The purpose of this study was to determine GRIT changes caused by participation of students majoring in science and engineering in taekwondo class. Effects of taekwondo ability on GRIT and academic achievement were also examined to determine structural relationships among taekwondo ability, GRIT, and academic achievement. We selected a total of 305 students (204 participants and 101 non-participants) as research subjects and conducted a GRIT (preliminary) measurement. After one-year of taekwondo class, we collected and statistically processed the data of GRIT (post) measurement, taekwondo ability, and academic achievement of the participants. Reliability analysis, technical statistics, paired sample t-test, correlation analysis, and path analysis were performed. Changes in the GRIT values of the participants were found to be greater than those of non-participants. It was also found that taekwondo ability, GRIT, and academic achievement had significant correlations with each other. Finally, it was found that the higher the taekwondo ability, the higher the academic achievement and the higher the GRIT. Moreover, the higher the GRIT, the higher the academic achievement. Taekwondo training increased the GRIT values of participants. In addition, the taekwondo ability had positive effects on GRIT and academic achievement. GRIT also had a positive effect on academic achievement. Thus, there were structural relationships among taekwondo ability, GRIT, and academic achievement.

Percent Body Fat Cut-Off Points for Diagnosing Metabolic Syndrome in Korean Adolescents.

BACKGROUND: This study aimed to identify percent body fat cut-off points related to metabolic syndrome in a large sample of Korean adolescents. METHODS: The subjects (n=2120; boys=1107, girls=1013) were middle and high school students aged 12-17 yr who participated in the Korean National Fitness Award Project in 2013. Percent body fat was estimated via eight-polar bioelectrical impedance analysis. Metabolic syndrome was classified using established standards based on the National Cholesterol Education Program with the definition modified for age. Age- and sex-specific percent body fat z-scores were calculated for every adolescent using skewness, median, and coefficient of variation curves to account for growth and development. Receiver operating characteristic curve analysis was used to identify the percent body fat cut-off points using percent body fat z-scores from skewness, median, and coefficient of variation curves as the test and metabolic syndrome as the criterion. RESULTS: Based on the modified National Cholesterol Education Program criteria for metabolic syndrome, the areas under the receiver operating characteristic curve for percent body fat were 0.882 and 0.893 for boys and girls, respectively. The percent body fat percentiles were 82.2 and 87.3 for boys and girls, respectively. According to the skewness, median, and coefficient of variation curves, the percent body fat cut-off points based on the modified National Cholesterol Education Program criteria were 23.6%-25.7% for boys and 32.8%-37.3% for girls, both aged 12-17 yr. Age- and sex-specific percent body fat cut-off points were identified in relation to the metabolic syndrome status of Korean adolescents. CONCLUSION: These percent body fat cut-offs might be useful for identifying metabolic abnormality due to obesity in Korean adolescents.

Physical Fitness Levels in Korean Adolescents: The National Fitness Award Project.

BACKGROUND: Although physical fitness in adolescents has been widely studied, there is the lack of information regarding developmental patterns of various youth fitness components. The LMS (L=skewness, M=median curve, and S=coefficient of variation) statistical method has been utilized to develop growth percentiles for height and weight as well as for fitness in the US and Europe countries. The purpose of this study was to develop age- and sex-specific smoothed percentile curves for fitness using the LMS method in Korean adolescents aged 13-18 years. METHODS: A sample of 14,794 adolescents (7,688 boys and 7,106 girls) who participated in the National Fitness Award Project in 2013 and 2014 was analyzed. The components were cardiorespiratory fitness (20-m PACER), muscle strength (handgrip strength), muscle endurance (partial curl-up, 30-s endurance jump), and flexibility (sit and reach). Age- and sex-specific smoothed percentile curves were calculated for fitness using the LMS method. RESULTS: Age- and sex-specific smoothed percentile curves (5th, 10th, 25th, 50th, 75th, 90th, and 95th) were presented for each fitness component. Except for flexibility, fitness levels were higher in boys than in girls. In general, performance in fitness components, except for partial curl-ups, increased with age in boys. However, in girls, performance in fitness components, except for partial curl-ups, slightly increased or remained stable. CONCLUSION: This study presented age- and sex-specific fitness percentile curves for Korean adolescents aged 13-18 years. This material might be useful in understanding and evaluating the fitness status of Korean adolescents.