Construction of a physical fitness evaluation index system and model for high-level freestyle skiing aerials athletes in China

OBJECTIVE

This study aims to enhance the competitive level of Chinese freestyle skiing aerials athletes by developing a specialized physical fitness evaluation index system and model tailored for high-level Chinese athletes. This system intends to provide theoretical references and training monitoring schemes in preparation for the 25th Milan Winter Olympics.

METHODS

A study was conducted on 29 high-level Chinese freestyle skiing aerials athletes. Physical fitness test indexes were selected using a literature review, expert interviews, and questionnaire surveys, and athletes were tested. Athletes were ensured to be in optimal physical condition before testing. Based on the test results, the representative indexes of the evaluation system are finally determined by combining R-type clustering analysis, multiple linear regression analysis. Determine index weights through weight questionnaires and normalization, and develop evaluation standards through methods such as percentile counting and weighted scoring.

RESULTS

Physical fitness evaluation system for Chinese freestyle skiing aerialists includes three aspects: evaluation index, index weight, and evaluation standard. The evaluation indexes include 3 first-level, 11 second-level, and 11 third-level indexes of body form, physiological function, and physical quality. In the evaluation weight, physical quality is ranked first, and physiological function and body form rank second and third, respectively. The evaluation standard consists of a scoring evaluation standard and a rating evaluation standard. Based on the index system, this study constructs the general and ideal physical fitness model of China's high-level freestyle aerials athletes.

CONCLUSION

The constructed physical fitness evaluation system effectively represents physical fitness development status of high-level freestyle skiing aerials athletes, providing a basis for creating personalized training plans. The established model serves as a reference for athletes' physical fitness development objectives.

CHANGES IN LOWER LIMB BONE DENSITY IN YOUNG JUMPERS

ABSTRACT Introduction The research on the exercise effect on the human bone density and skeletal muscle content mainly focuses on the middle-aged and elderly population. However, few studies on different sports’ effects upon bone and muscle density in college students and adolescents. Objective Study the effect of physical training on bone density and lower limb jumping ability in young people. Methods The relationship between bone mineral density and lower limb jumping ability was analyzed by mathematical statistics. Male individuals aged 10-20 years were divided into the early adolescence group (n=26) and late adolescence group (n=37). According to training status, they were divided into preadolescent athletic group (n=11), non-athletic group (n=15); puberty athletic group (n=11) and non-athletic group (n=15). The following indicators were used: bone density, vertical jump test, continuous vertical jump test, RDJ index. Results Athletes’ bone mineral density (BMD) is related to their muscle strength. These results suggest a certain internal connection between the (BMD) of bone tissue and the development of muscle strength. Therefore, there is evidence of differences in lower limb bone mineral density and jumping ability between the two groups. Conclusion Bone mineral density in the lower limbs of adolescents is correlated with jumping ability. Exercise can help improve bone density in adolescents. Evidence level II; Therapeutic Studies - Investigating the results.

Bone Density and Bone Geometry in University Athletes From Sports With Different Levels of Impact: Simultaneous Association With Multiple Factors

ABSTRACT

Moraes, MS, Fernandes, RA, Moreno, YMF, Pelegrini, A, and Silva, DAS. Bone density and bone geometry in university athletes from sports with different levels of impact: simultaneous association with multiple factors. J Strength Cond Res XX(X): 000-000, 2022-The aim of this study was to use the bone loading unit (BLU) classification to compare bone density and bone geometry of sports with different levels of impact, simultaneously controlling the multiple factors that interfere with bone metabolism in athletes. Overall, 167 university athletes (92 men) participated in the study. Bone mineral density (BMD), strength index, cross-sectional area (CSA) at the moment of inertia, section modulus (Z), CSA, neck-shaft angle (NSA), and hip axis length (HAL) were measured. Sports were categorized by level of impact, high BLU (higher impact) and moderate/low BLU (lower impact). Covariates were fat mass, lean tissue mass, training volume, time of practice, dietary supplementation, use of oral contraceptives and menstrual status. Multiple linear regression with 5% significance level (p < 0.05) was used. In men, HAL was higher in sports with high BLU compared with those with moderate/low BLU (β: -0.21; R2: 0.30; p = 0.03). In women, NSA was higher in sports with moderate/low BLU compared with those with high BLU (β: 0.31; R2: 0.11; p = 0.02). There was no difference between BLU groups for BMD. These results persisted when the simultaneous interference of covariates was controlled. Thus, this study recommends BLU to classify sports and reinforces the importance of monitoring HAL and NSA in athletes in addition to the control of multiple factors that interfere with bone metabolism, because they influence physical performance and bone health during and after athletic life.

30-Second Chair Stand Test Predicts Countermovement Jump Performance in Young Adults

BACKGROUND

The countermovement jump (CMJ) is a valid and reliable test of lower extremity (LE) muscle power. However, the CMJ may not be appropriate during early-stage rehabilitation of injuries. Functional muscle strength tests (FMSTs) could evaluate LE muscle power with lower joint reaction forces.

HYPOTHESIS

The lateral step-up test (LSUT), 5 times sit to stand (5×STS), and 30-s chair stand test (30CST) could predict CMJ jump height (JHt) and jump peak power (JPow).

STUDY DESIGN

Cross-sectional study.

LEVEL OF EVIDENCE

Level 2.

METHODS

Eighty-one young adults performed 3 CMJs to measure JHt and JPow using an electronic jump mat and speed analyzer. Participants also performed three FMSTs: 1 trial of the LSUT and a modified trial of LSUT touching the ground with the heel only (MLSUT); 2 trials of the 5×STS; and 2 trials of the 30CST, in a randomized order. Spearman rho correlations and hierarchal multiple linear regressions were used to determine whether FMST performances predicted JHt and JPow, after controlling for sex, body height, and body mass.

RESULTS

30CST, LSUT, MLSUT, sex, body mass, and body height were significantly associated with JHt (P < 0.05). LSUT, sex, body height, and body mass were significantly associated with JPow (P < 0.05). Hierarchical regression analyses showed that the 30CST significantly predicted JHt (P < 0.01) and JPow (P = 0.03), independent of sex, body height, and body mass.

CONCLUSION

30CST performance predicted JHt and JPow in young adults.

CLINICAL RELEVANCE

The 30CST is easy to perform, requires equipment found readily in clinics, and predicts LE muscle power. This test could be used to track progress during the early stages of LE injury rehabilitation.

Interscholastic Athletics and Bone Strength: The Iowa Bone Development Study

ABSTRACT

Pashkova, A, Hartman, JM, Letuchy, EM, and Janz, KF. Interscholastic athletics and bone strength: the Iowa bone development study. J Strength Cond Res 36(5): 1271-1276, 2022-The objective of this study was to determine the relationship between adolescents' participation in various interscholastic sports and differences in bone strength outcomes. Subjects (N = 380) were recruited from the Iowa Bone Development Study and categorized based on sport participation into 3 power groups: no-power, low-power, and high-power. Sports such as basketball, cheerleading/poms, gymnastics, volleyball, track, football, tennis, and soccer were considered high-power. Peripheral quantitative computed tomography (pQCT) was used to determine bone measures of polar stress-strain index (measure of torsion strength), cortical content (measure of cortical bone size and area at the 66% tibia site), and bone strength index (measure of compression strength based on total bone density and area at the 4% tibia site). Adjusted pairwise comparison for group least squares means high-power sport participation compared with no-power sport participation showed significant differences in all bone strength outcomes for both men and women (p value < 0.01). There was a significant difference in all bone strength measures between low-power and no-power groups for men (p value < 0.05), but not women. Because of decreasing levels of physical activity in late adolescence, the promotion of high-power sports may be particularly important for optimal bone development in the final years before peak bone mass.

How is the phase angle associated with total and regional bone mineral density in university athletes?. Physiol Meas 2021;42. [PMID: 34225269 DOI: 10.1088/1361-6579/ac114b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0]

Objective.To investigate how phase angle (PhA) is associated with total and regional bone mineral density (BMD) (femur and lumbar spine) in university athletes.Approach.This cross-sectional study was conducted in Florianópolis, Brazil, with 167 university athletes from different sports (92 males). The PhA was obtained through electrical bioimpedance and BMD was obtained through dual x-ray absorptiometry (DXA). Data on the covariables age, time involved in the sport, type of sport (low, medium and high impact), daily use of oral contraceptives, and vitamin D calcium and/or protein supplementation were obtained through anamnesis, while fat mass and fat- and bone-free mass were obtained through DXA. Simple linear regression and a 5% significance level were used.Main results. In female athletes, PhA was directly associated with total BMD (β: 2.20; 95% CI: 0.43; 3.96) and BMD in the femur (β0.85; 95% CI: -0.23; 1.94) and lumbar spine (β: 1.45; 95% CI: 0.44; 2.46), even after adjusting for the covariates. In male athletes, although PhA was directly associated with regional BMD (femur [β: 0.63; 95% CI: 0.04; 1.22] and lumbar spine [β: 0.64; 95% CI: -0.01; 1.31]) in simple linear regression, this association disappeared when the covariates were added.Significance. PhA was directly associated with total BMD and lumbar spine in female, but not male, athletes.

Contribution of High School Sport Participation to Young Adult Bone Strength

INTRODUCTION

Nearly 8 million American adolescents participate in sports. Participation declines in young adulthood.

PURPOSE

This study assessed longitudinal effects of high school sport participation and muscle power on young adult bone strength.

METHODS

Two hundred twenty-eight young adults from the Iowa Bone Development Study completed an interscholastic sport participation questionnaire. Current physical activity (PA) behaviors were assessed via questionnaire. Dual x-ray absorptiometry assessed hip areal bone mineral density and was used with hip structure analysis to estimate femoral neck section modulus and hip cross-sectional area. Peripheral quantitative computed tomography provided strength-strain index and bone strength index at 38% and 4% midshaft tibial sites, respectively. Vertical jump estimated muscle power at 17 yr. Sex-specific multiple linear regression predicted young adult bone outcomes based on sport participation groups. Mediation analysis analyzed the effects of muscle power on relationships between sport participation and bone strength.

RESULTS

At follow-up, males participating in any interscholastic sport had greater bone strength than males who did not participate in sport. The explained variability in bone outcomes was 2% to 16%. Females who participated in sports requiring muscle power had greater bone strength than females who did not participate in sports or females who participated in nonpower sports (explained variability was 4%-10%). Muscle power mediated 24.7% to 41% of the effect of sport participation on bone outcomes in males and 19.4% to 30% in females.

CONCLUSIONS

Former male interscholastic sport participants and female interscholastic power sport participants have stronger bones than peers even when adjusting for current PA. Muscle power did not fully explain differences in all bone outcomes, suggesting that sport participation has additional bone health benefits.

The reliability of vertical jump tests between the Vertec and My Jump phone application

Background

The vertical jump is used to estimate sports performance capabilities and physical fitness in children, elderly, non-athletic and injured individuals. Different jump techniques and measurement tools are available to assess vertical jump height and peak power; however, their use is limited by access to laboratory settings, excessive cost and/or time constraints thus making these tools oftentimes unsuitable for field assessment. A popular field test uses the Vertec and the Sargent vertical jump with countermovement; however, new low cost, easy to use tools are becoming available, including the My Jump iOS mobile application (app). The purpose of this study was to assess the reliability of the My Jump relative to values obtained by the Vertec for the Sargent stand and reach vertical jump (VJ) test.

Methods

One hundred and thirty-five healthy participants aged 18–39 years (94 males, 41 females) completed three maximal Sargent VJ with countermovement that were simultaneously measured using the Vertec and the My Jump. Jump heights were quantified for each jump and peak power was calculated using the Sayers equation. Four separate ICC estimates and their 95% confidence intervals were used to assess reliability. Two analyses (with jump height and calculated peak power as the dependent variables, respectively) were based on a single rater, consistency, two-way mixed-effects model, while two others (with jump height and calculated peak power as the dependent variables, respectively) were based on a single rater, absolute agreement, two-way mixed-effects model.

Results

Moderate to excellent reliability relative to the degree of consistency between the Vertec and My Jump values was found for jump height (ICC = 0.813; 95% CI [0.747–0.863]) and calculated peak power (ICC = 0.926; 95% CI [0.897–0.947]). However, poor to good reliability relative to absolute agreement for VJ height (ICC = 0.665; 95% CI [0.050–0.859]) and poor to excellent reliability relative to absolute agreement for peak power (ICC = 0.851; 95% CI [0.272–0.946]) between the Vertec and My Jump values were found; Vertec VJ height, and thus, Vertec calculated peak power values, were significantly higher than those calculated from My Jump values (p < 0.0001).

Discussion

The My Jump app may provide a reliable measure of vertical jump height and calculated peak power in multiple field and laboratory settings without the need of costly equipment such as force plates or Vertec. The reliability relative to degree of consistency between the Vertec and My Jump app was moderate to excellent. However, the reliability relative to absolute agreement between Vertec and My Jump values contained significant variation (based on CI values), thus, it is recommended that either the My Jump or the Vertec be used to assess VJ height in repeated measures within subjects’ designs; these measurement tools should not be considered interchangeable within subjects or in group measurement designs.