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1.
Abstract

The aims of this study were to determine the validity of fat mass of the trunk as a predictor for visceral fat area at the umbilicus level and to develop equations to predict visceral fat mass at the umbilicus level using fat mass of the trunk measured by dual-energy X-ray absorptiometry (DXA) and bioelectrical impedance analysis (BIA). The participants were 121 normal Japanese adults (69 males, 52 females). Another 60 volunteer adults (34 males, 26 females) were recruited for examination of cross-validity. Altogether, 41 adults (15 males, 26 females) in the original group and 19 adults (7 males, 12 females) in the cross-validity group received BIA measurement. We measured fat mass by DXA and the BIA system, which was a single-frequency BIA with 8-point contact electrodes, and visceral fat area by computed tomography. We observed significant correlations for visceral fat area in waist circumference (0.56) and fat mass of the trunk measured by DXA (0.64). There was no significant difference in fat mass of the trunk between the DXA and BIA systems, but the BIA system tended to provide an underestimate compared with DXA. With combined fat mass of the trunk measured by DXA and waist circumference as predictors, visceral fat area was estimated by equation (1) (R = 0.87, R 2 = 0.76, standard error of the estimate = 20.9 cm2). When substituting fat mass of the trunk measured by BIA into equation (1), there was no significant difference in visceral fat area between the reference and predicted values. An equation using fat mass of the trunk measured by BIA (equation 2) was obtained (R = 0.89, R 2 = 0.78, standard error of the estimate = 20.7 cm2), but a systematic error was found for the males. There was cross-validity in both equations. In conclusion, fat mass of the trunk is an effective predictor for the visceral fat area at the umbilicus level. Fat mass of the trunk measured by BIA might be a valid method to predict visceral fat, although further studies with larger samples taking into account the extent and type of obesity are required.  相似文献   

2.
Accurate measurement of head volume is indispensable for precise assessments of body composition determined by hydrostatic weighing without head submersion. The purpose of this study was to establish a prediction equation for head volume measured by the immersion method from multiple regression analysis using head parameters (head circumference, head length, head breadth, neck girth and head thickness) as independent variables. The participants were 106 Japanese young adults (55 males and 51 females) aged 17?–?27 years. Intra-class correlation coefficients (ICCs) for each head parameter and head volume in males and females were very high (ICC = 0.993?–?0.999, 0.992?–?0.998). Head circumference was closely related to head volume measured by the immersion method (r = 0.719, 0.861, P <?0.05), and was the most important parameter for the prediction equation in both sexes. Head breadth was related poorly (r = 0.475, 0.500, P <?0.05) and showed a small individual difference. It was, therefore, excluded from the independent variables. The prediction equation for males was predicted head volume = 122.10X 1 + 106.19X 3 + 37.16X 4 - 89.46X 5 - 4754.93, R = 0.909, SEE = 121.75?ml, and that for females was predicted head volume = 213.83X 1 + 45.24X 3 + 36.85X 4 - 74.34X 5 - 8912.43, R = 0.913, SEE = 136.26?ml (where X 1 = head circumference, X 3 = head length, X 4 = neck girth, X 5 = head thickness, and SEE = standard error of the estimate). The limits of agreement for predicted and measured head volume were –?234.5 to 234.1?ml for males, and ??261.0 to 261.0?ml for females. In cross-validation groups of both sexes, there were no significant differences between measured head volume and predicted head volume. The correlation coefficients between measured head volume and predicted head volume in males and females were 0.894 and 0.908, respectively. The predicted head volume from prediction equations was considered to have high reliability and validity.  相似文献   

3.
Abstract

The purpose of this study was to examine the accuracy and reliability of whole-body volume, body density, and percent body fat calculated from body volume without the head (V NH), as assessed by hydrostatic weighing without head submersion and predicted head volume (pV H) based on head parameters, as compared with standard hydrostatic weighing. Participants comprised 29 males and 27 females aged 17–26 years. Head volume was predicted from anthropometric head parameters using a prediction equation. Underwater weights with/without head submersion were measured five times. The reliability of underwater weighing without head submersion was very good (intraclass correlation coefficient: males=0.998, females=0.998) as was that for traditional head submersion. The relationship between the sum of V NH and pV H and the whole-body volume measured by hydrostatic weighing was very high (males=0.998, females=0.999), and their values were very similar with an error range of 300–400 ml. Although percent body fat assessed from the sum of V NH and pV H showed a slight scatter of 2–3% from the identity line of percent body fat assessed by hydrostatic weighing, the relationships for both sexes were very strong (males=0.918, females=0.957). The errors (2 standard deviations) as determined by Bland-Altman plots between the two methods were ?3.2 to 2.6% in males and ?2.3 to 2.8% in females. There was no significant bias in percent body fat estimated by the two methods (hydrostatic weighing with/without head submersion), and the sum of V NH and pV H could validly estimate body composition, regardless of physical size. It is suggested that hydrostatic weighing without head submersion is a valid and convenient alternative technique.  相似文献   

4.
Abstract

The purpose of this study was to validate and cross-validate the Beunen-Malina-Freitas method for non-invasive prediction of adult height in girls. A sample of 420 girls aged 10–15 years from the Madeira Growth Study were measured at yearly intervals and then 8 years later. Anthropometric dimensions (lengths, breadths, circumferences, and skinfolds) were measured; skeletal age was assessed using the Tanner-Whitehouse 3 method and menarcheal status (present or absent) was recorded. Adult height was measured and predicted using stepwise, forward, and maximum R 2 regression techniques. Multiple correlations, mean differences, standard errors of prediction, and error boundaries were calculated. A sample of the Leuven Longitudinal Twin Study was used to cross-validate the regressions. Age-specific coefficients of determination (R 2) between predicted and measured adult height varied between 0.57 and 0.96, while standard errors of prediction varied between 1.1 and 3.9 cm. The cross-validation confirmed the validity of the Beunen-Malina-Freitas method in girls aged 12–15 years, but at lower ages the cross-validation was less consistent. We conclude that the Beunen-Malina-Freitas method is valid for the prediction of adult height in girls aged 12–15 years. It is applicable to European populations or populations of European ancestry.  相似文献   

5.
Abstract

This study attempted to validate an anthropometric equation for predicting age at peak height velocity (APHV) in 193 Polish boys followed longitudinally 8–18 years (1961–1972). Actual APHV was derived with Preece–Baines Model 1. Predicted APHV was estimated at each observation using chronological age (CA), stature, mass, sitting height and estimated leg length. Mean predicted APHV increased from 8 to 18 years. Actual APHV was underestimated at younger ages and overestimated at older ages. Mean differences between predicted and actual APHV were reasonably stable between 13 and 15 years. Predicted APHV underestimated actual APHV 3 years before, was almost identical with actual age 2 years before, and then overestimated actual age through 3 years after PHV. Predicted APHV did not differ among boys of contrasting maturity status 8–11 years, but diverged among groups 12–15 years. In conclusion, predicted APHV is influenced by CA and by early and late timing of actual PHV. Predicted APHV has applicability among average maturing boys 12–16 years in contrast to late and early maturing boys. Dependence upon age and individual differences in actual APHV limits utility of predicted APHV in research with male youth athletes and in talent programmes.  相似文献   

6.
The purpose of this study was to develop a step test with a personalized step rate and step height to predict cardiorespiratory fitness in 80 college-aged males and females using the self-reported perceived functional ability scale and data collected during the step test. Multiple linear regression analysis yielded a model (R = 0.90, SEE = 3.43 mL·kg?1·min?1) that included gender, body mass, perceived functional ability, step rate, and recovery heart rate. Based on the standardized β-weights, gender explained the largest proportion of variance in VO2max values followed by perceived functional ability. The cross validation predicted residual sum of squares statistics show minimal shrinkage (RPRESS = 0.88, SEEPRESS = 3.57 mL·kg?1·min?1) in the accuracy of the regression model. This study provides a model to predict VO2max from non-exercise data and data collected during an individualized multistage step test that is accurate, time-efficient, and easy to administer.  相似文献   

7.
A number of field-based investigations have evidenced practically significant relationships between clubhead velocity (CHV), vertical jump performance and maximum strength. Unfortunately, whilst these investigations provide a great deal of external validity, they are unable to ascertain vertical ground reaction force (vGRF) variables that may relate to golfers’ CHVs. This investigation aimed to assess if the variance in European Challenge Tour golfers’ CHVs could be predicted by countermovement jump (CMJ) positive impulse (PI), isometric mid-thigh pull (IMTP) peak force (PF) and rate of force development (RFD) from 0–50 ms, 0–100 ms, 0–150 ms and 0–200 ms. Thirty-one elite level European Challenge Tour golfers performed a CMJ and IMTP on dual force plates at a tournament venue, with CHV measured on a driving range. Hierarchical multiple regression results indicated that the variance in CHV was significantly predicted by all four models (model one R2 = 0.379; model two R2 = 0.392, model three R2 = 0.422, model four R2 = 0.480), with Akaike’s information criterion indicating that model one was the best fit. Individual standardised beta coefficients revealed that CMJ PI was the only significant variable, accounting for 37.9% of the variance in European Challenge Tour Golfers’ CHVs.  相似文献   

8.
PurposeTo evaluate the potential of a year-round school calendar (180-day school year distributed across 12 months) as an intervention compared to a traditional school calendar (180-day school year distributed across 9 months) for mitigating children's weight gain and fitness loss via a natural experiment.MethodsHeight, weight, and cardiorespiratory fitness (CRF) (i.e., Fitnessgram Progressive Aerobic Cardiovascular Endurance Run) were measured in children (5–12 years old) in 3 schools (2 traditional, 1 year-round, n = 990 students, age = 8.6 ± 2.4 years, 53.1% male, 68.9% African American) from 1 school district. Structure (represented by the presence of a school day) was the independent variable. Changes in body mass index (BMI), age- and sex-specific BMI z-scores (zBMI), BMI percentile, percent of overweight or obese children, and CRF (Progressive Aerobic Cardiovascular Endurance Run laps completed) were assessed for summer 2017 (May–August 2017), school year 2017/2018 (August 2017–May 2018), and summer 2018 (May–August 2018). Primary analyses examined the overall change in weight and CRF from summer 2017 until summer 2018 via multilevel mixed effects regression, with group (traditional vs. year-round calendar), time, and a group-by-time interaction as the independent variables. Secondary regression analyses estimated differences in change within and between groups during each time period, separately.ResultsYear-round students gained less BMI (difference in ∆ = –0.44, 95% confidence interval (CI): –0.67 to –0.03) and less CRF (difference in ∆ = –1.92, 95%CI: –3.56 to –0.28) than students attending a traditional school overall. Compared with traditional students, during both summers, year-round students gained less BMI (summer 2017 difference in ∆ = –0.15, 95%CI: –0.21 to –0.08; summer 2018 difference in ∆ = –0.16, 95%CI: –0.24 to –0.07) and zBMI (summer 2017 difference in ∆ = –0.032, 95%CI: –0.050 to –0.010; summer 2018 difference in ∆ = –0.033, 95%CI: –0.056 to –0.009), and increased CRF (summer 2017 difference in ∆ = 0.40, 95%CI: 0.02–0.85; summer 2018 difference in ∆ = 0.23, 95%CI: –0.25 to 0.74). However, the opposite was observed for the school year, with traditional students gaining less BMI and zBMI and increasing CRF compared with year-round students (difference in BMI ∆ = 0.05, 95%CI: 0.03–0.07; difference in zBMI ∆ = 0.012, 95%CI: 0.005–0.019; difference in Progressive Aerobic Cardiovascular Endurance Run laps ∆ = –0.43, 95%CI: –0.58 to –0.28).ConclusionThe year-round school calendar had a small beneficial impact on children's weight status but not CRF. It is unclear if this benefit to children's weight would be maintained because gains made in the summer were largely erased during the school year. Trajectories of weight and CRF gain/loss were consistent with the structured days hypothesis.  相似文献   

9.
The purpose of this study was to develop an age-generalized regression model to predict maximal oxygen uptake (VO2max) based on a maximal treadmill graded exercise test (GXT; George, 1996) George, J. D. 1996. Alternative approach to maximal exercise testing and VO2max prediction in college students. Research Quarterly for Exercise and Sport, 67: 452–457. [Taylor & Francis Online], [Web of Science ®] , [Google Scholar]. Participants (N?=?100), ages 18–65 years, reached a maximal level of exertion (mean?±?standard deviation [SD]; maximal heart rate [HRmax]?=?185.2?±?12.4 beats per minute (bpm); maximal respiratory exchange ratio [RERmax]?=?1.18?±?0.05; maximal rating of perceived exertion (RPEmax)?=?19.1?±?0.7) during the GXT to assess VO2max (mean?±?SD; 40.24?±?9.11 mL·kg?1·min?1). Multiple linear regression generated the following prediction equation (R?=?.94, standard error of estimate [SEE]?=?3.18 mL·kg?1·min?1, %SEE?=?7.9): VO2max (mL·kg?1·min?1)?=?13.160?+?(3.314 × gender; females?=?0, males?=?1) ? (.131 × age) ? (.334 × body mass index (BMI))?+?(5.177 × treadmill speed; mph)?+?(1.315 × treadmill grade; %). Cross validation using predicted residual sum of squares (PRESS) statistics revealed minimal shrinkage (Rp ?=?.93 and SEE p ?=?3.40 mL·kg?1·min?1); consequently, this model should provide acceptable accuracy when it is applied to independent samples of comparable adults. Standardized β-weights indicate that treadmill speed (.583) was the most effective at predicting VO2max followed by treadmill grade (.356), age (?.197), gender (.183), and BMI (?.148). This study provides a relatively accurate regression model to predict VO2max in relatively fit men and women, ages 18–65 years, based on maximal exercise (treadmill speed and grade), biometric (BMI), and demographic (age and gender) data.  相似文献   

10.
Abstract

The purpose of this study was to develop a regression equation to predict maximal oxygen uptake (VO2max) based on nonexercise (N-EX) data. All participants (N= 100), ages 18–65 years, successfully completed a maximal graded exercise test (GXT) to assess VO2max (M= 39.96 mL·kg -1· min -1 , SD = 9.54). The N-EX data collected just before the maximal GXT included the participant's age; gender; body mass index (BMI); perceived functional ability (PFA) to walk, jog, or run given distances; and current physical activity (PA-R) level. Multiple linear regression generated the following N-EX prediction equation (R = .93, SEE = 3.45 mL·kg -1· min -1 , %SEE= 8.62): VO2max (mL·kg -1· min -1 ) = 48.0730 + (6.1779 x gender; women = 0, men = 1) – (0.2463 x age) – (0.6186 x BMI) + (0.7115 x PFA) + (0.6709 x PA-R). Cross validation using PRESS (predicted residual sum of squares) statistics revealed minimal shrinkage (R p = .91 and SEE p = 3.63 mL·kg -1· min -1 ); thus, this model should yield acceptable accuracy when applied to an independent sample of adults (ages 18–-65 years) with a similar cardiorespiratory fitness level. Based on standardized β-weights, the PFA variable (0.41) was the most effective at predicting VO2max followed by age (-0.34), gender (0.33), BMI (-0.27), and PA-R (0.16). This study provides a N-EX regression model that yields relatively accurate results and is a convenient way to predict VO2max in adult men and women.  相似文献   

11.
The purpose of this study was to assess the accuracy of three recommended anthropometric equations for women and then develop an updated prediction equation using dual energy x-ray absorptiometry (DXA). The percentage of body fat (%BF) by anthropometry was significantly correlated (r = .896-.929; p < .01) with DXA, but each equation underestimated %BF (3.2-5.6 %BF; p < .01). The following DXA criterion (DC) equation was created: %BF= -6.40665 + 0.41946(S3SF) - 0.00126(S3SF)2 + 0.12515(hip) + 0.06473 (age); (S3SF = sum of triceps, suprailiac, thigh; hip = circumference in cm; age = years). The predicted residual sum of squares (PRESS) R2 was high (0.86), and the PRESS standard error of estimate (SEE) was low (2.5 %BF) for our sample of 150 women. The DC equation was further crosschecked on a separate sample of women (n = 25) and again showed excellent agreement. The DC equation appears to be a more accurate estimation of %BF in women.  相似文献   

12.
We evaluated the impact of bilateral leg extension power and fat-free mass on 2000?m rowing ergometer performance in 332 young oarsmen (age 21±2 years, height 1.76±0.05?m, body mass 62±6?kg; mean±s). The 2000?m rowing performance time was correlated with height (1.62–1.93?m; R 2?=?0.23, P?<0.001), body mass (53–95?kg; R 2?=?0.53, P?<0.001), fat-free mass (47–82?kg; R 2?=?0.58, P?<0.001) and bilateral leg extension power (1202–3302?W; R 2?=?0.38, P?<0.001). Multiple regression analysis selected fat-free mass and bilateral leg extension power as regressor variables. Fat-free mass explained 58% of the variability in rowing performance and the inclusion of bilateral leg extension power improved the power of prediction by 5%. The results suggest that rowing involves almost every muscle in the body and that bilateral leg extension power is very important during this activity.  相似文献   

13.
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14.
Abstract

We previously proposed two predictive equations of visceral fat area applicable in a field setting (Demura & Sato, 2007a Demura, S. and Sato, S. 2007a. Prediction of visceral fat area at the umbilicus level using fat mass of the trunk: The validity of bioelectrical impedance analysis. Journal of Sports Sciences, 25: 823–833. [Taylor & Francis Online], [Web of Science ®] , [Google Scholar], 2007b Demura, S. and Sato, S. 2007b. Prediction of visceral fat area in Japanese adults: Proposal of prediction method applicable in a field setting. European Journal of Clinical Nutrition, 61: 727–735. [Crossref], [PubMed], [Web of Science ®] , [Google Scholar]). One uses the fat mass of the trunk measured by bioelectrical impedance as the main predictor (equation 1) and the other uses internal fat mass estimated from several anthropometric variables (equation 2). In this study, we examined the inter- and intra-individual accuracy of estimated values using these equations after 8 weeks of exercise training. Participants were 42 Japanese adults aged 42.7 ± 10.3 years (22 males, 20 females). Visceral fat area, body composition, and blood biochemistry were measured at baseline and after 8 weeks. There were no significant differences in reference visceral fat area measured by computed tomography and visceral fat area predicted by the equations either at baseline or after 8 weeks, and the values were highly consistent (equation 1: baseline R 2 = 0.829, after R 2 = 0.860; equation 2: baseline R 2 = 0.832; after R 2 = 0.850). No significant relationship was observed between the reference and change in visceral fat area for equation 1 (males: r = 0.272, P > 0.05; females: r = 0.428, P > 0.05), but there was a significant relationship for females with equation 2 (males: r = 0.279, P > 0.05; females: r = 0.474, P <0.05). Our findings indicate that these equations have high inter-individual consistency but low intra-individual consistency with the reference and are of limited use for the longitudinal evaluation of visceral fat area.  相似文献   

15.
Abstract

The effects of exercise training on heart have been widely explored. However, less understood are the effects of dehydration and rehydration on electrocardiographic (ECG) and echocardiographic (Echo) parameters in wrestlers. The aim of this study was to determine the effect of dehydration and rehydration on some ECG and Echo parameters. Fourteen healthy high school wrestlers (age 18.1±2.6 years, weight 77.2±10.2 kg, BMI 25.2±2.9 kg · m?2; mean±s) were randomly assigned to an experimental (loss of 3–4% of their weight through 10-min bouts in dry sauna) or a control (dry sauna exposure with mineral water proportionate to their body weight loss) group. Blood and urine sampling, 12-lead ECG, and echocardiogram were recorded in euhydration, dehydration, and 18 h after sauna. Moreover, a 6-min high-intensity arm ergometer cranking test (8×15 s intervals at maximum workload and 30 s active recovery) was completed in each of the three stages. Data were analysed with repeated-measures analysis of variance, independent t-tests, and Pearson correlations. Dehydration by 3–4% of body weight in sauna resulted in augmentation of the sum of amplitudes of P waves and QRS complexes (mm), but decreased left ventricular end-systolic volume (LVESV), left ventricular end-diastolic volume (LVEDV), and stroke volume (ml). As expected, rehydration was associated with recovery of the P wave and ECG parameters. In general, QRS amplitude correlated poorly with LVESV, LVEDV, and P wave, but was inversely related to stroke volume (r=–0.387, P=0.011). In conclusion, dehydration in Greco-Roman wrestlers results in physiological alterations (amplitude of the P wave and QRS complex, LVESV, LVEDV, and stroke volume) of the electrical properties of the passive volume conductor. Further research is necessary to assess the potential for adverse events and appropriateness of this short-term weight loss strategy for young wrestlers or other populations.  相似文献   

16.
ABSTRACT

School-based sports and physical education play an important role in the development of youth (Jones, Edwards, et al., 2017), but participation in athletics is unequal for lesbian, gay, bisexual, transgender, and queer (LGBTQ) youth compared to their straight/cisgender peers [Greenspan, S. B., Griffith, C., & Murtagh, E. F. (2017). LGBTQ youths’ school athletic experiences: A 40-year content analysis in nine flagship journals. Journal of LGBT Issues in Counseling, 11(3), 190–200]. Sport cultures, generally, recreate dynamics of exclusion for marginalized youth. However, there are opportunities to transform these spaces into more inclusive and positive environments to support positive growth for all young people [Newman, T., Alvarez, A., & Kim, M. (2017). An experiential approach to sport-based positive youth development. Journal of Experiential Education, 40(3), 308–322]. Our study uses a data set of adolescents, collected as part of a community-based participatory action research project led by high school students in southeast Michigan, USA. Respondents reported their sexual and gender identities, as well as experiences in youth sport, as well as safety using sex-segregated facilities (i.e., bathrooms and locker-rooms). Using mediation models based on linear regression, we found evidence that LGBQ high school students play sports at a significantly lower rate compared to straight students, and among those who play sports, LGBTQ respondents felt significantly less safe compared to straight and cisgender students. Opposite to the LGBQ and trans youth in this study, straight/cisgender youth also reported feeling safer using all facilities. The mediation models suggest that these inequalities help to explain disparities in rates of sports participation and feelings of safety while participating. These findings have important implications for policy, practice, and future research.  相似文献   

17.
ABSTRACT

The purpose of this study was to validate an alternative skinfold equation for women created from dual-energy x-ray absorptiometry (DXA). Anthropometrics and a whole-body DXA scan were completed on 77 women (mean age: 28.0 ± 10.2 years). Four Jackson-Pollack (JP) skinfold prediction equations and the DXA criterion (DC) equation were compared to DXA-derived body fat percentage (%BF). One-way repeated measures ANOVA revealed significant differences (p ≤ .001) in the %BF with post hoc-comparisons revealing significant differences among JP7 (21.3 ± 5.7), JP4 (21.4 ± 5.7), JP3a (22.2 ± 5.9), and JP3b (22.6 ± 5.7) when compared to the DXA-derived %BF; no significant difference existed between DC %BF (26.5 ± 5.6) and DXA-derived %BF (26.5 ± 5.4) (p = 1.0). The DC equation more accurately predicted %BF in women volunteers compared to Jackson-Pollack equations.  相似文献   

18.
PurposeThe coronavirus disease-2019 (COVID-19) pandemic in the United States led to nationwide stay-at-home orders and school closures. Declines in energy expenditure resulting from canceled physical education classes and reduced physical activity may elevate childhood obesity risk. This study estimated the impact of COVID-19 on childhood obesity.MethodsA microsimulation model simulated the trajectory of a nationally representative kindergarten cohort's body mass index z-scores and childhood obesity prevalence from April 2020 to March 2021 under the control scenario without COVID-19 and under the 4 alternative scenarios with COVID-19—Scenario 1: 2-month nationwide school closure in April and May 2020; Scenario 2: Scenario 1 followed by a 10% reduction in daily physical activity in the summer from June to August; Scenario 3: Scenario 2 followed by 2-month school closure in September and October; and Scenario 4: Scenario 3 followed by an additional 2-month school closure in November and December.ResultsRelative to the control scenario without COVID-19, Scenarios 1, 2, 3, and 4 were associated with an increase in the mean body mass index z-scores by 0.056 (95% confidence interval (95%CI): 0.055–0.056), 0.084 (95%CI: 0.084–0.085), 0.141 (95%CI: 0.140–0.142), and 0.198 (95%CI: 0.197–0.199), respectively, and an increase in childhood obesity prevalence by 0.640 (95%CI: 0.515–0.765), 0.972 (95%CI: 0.819–1.126), 1.676 (95%CI: 1.475–1.877), and 2.373 (95%CI: 2.135–2.612) percentage points, respectively. Compared to girls and non-Hispanic whites and Asians, the impact of COVID-19 on childhood obesity was modestly larger among boys and non-Hispanic blacks and Hispanics, respectively.ConclusionPublic health interventions are urgently called to promote an active lifestyle and engagement in physical activity among children to mitigate the adverse impact of COVID-19 on unhealthy weight gains and childhood obesity.  相似文献   

19.
Abstract

This study investigated the relationship between the physical abilities of adolescent rugby league players and tackling and ball-carrying skills performed during matches, across three seasons (under-15 to under-17). The players were measured each season for acceleration (10–30 m), peak and mean speed (10–30 m), sprinting force (10–30 m), aerobic power, counter-movement jump (CMJ) height and jumping power. The matches were filmed and analysed for ball-carrying and tackling frequency per minute (successful and unsuccessful outcomes). There were strong relationships between successful carries?min–1 and 10 m force in the under-15 (R = 0.61, P < 0.001), under-16 (R = 0.69, P < 0.001) and under-17 groups (R = 0.64, P < 0.001). There were also strong and moderate relationships between predicted vertical power and successful carries?min–1 in the under-15 (R = 0.63, P = 0.011) and under-17 group (R = 0.40, P = 0.030), respectively. There were no relationships between carries or tackles and any other performance indicators. These findings suggest that acceleration, in accordance with gains in body mass, support ball-carrying but not tackling performance. Performance measurements, such as CMJ or aerobic power, do not support ball-carrying ability among youth rugby league players.  相似文献   

20.
Abstract

The aim of this study was to compare equations for estimating percentage body fat from skinfold thickness in elite sport climbers by assessing their agreement with percentage body fat measured using dual-energy X-ray absorptiometry (DXA). Skinfold thickness was measured in a convenience sample of 19 elite sport climbers [9 women and 10 men; mean age 31.2 years (s = 5.0) and 28.6 years (s = 3.6), respectively]. Percentage body fat was estimated using 17 different equations, and it was also measured by DXA. A significant inter-methods difference was observed for all equations, except for Durnin's equation in men (inter-methods difference: ?0.57% and ?0.29%; 1.96 s: 5.56 and 5.23 for Siri's and Brozek's equation, respectively) and women (inter-methods difference: ?0.67% and ?1.29% for Siri's and Brozek's equation, respectively), and for Wilmore's equation using Siri's body fat equation in women (inter-methods difference: ?1.86%). In women, the limits of agreement were lower when using Durnin's equation compared with Wilmore's equation (1.96 s: 3.86% and 5.13%, respectively). In conclusion, of the 17 studied equations, Durnin's equation was the most accurate in estimating percentage body fat in both male and female elite climbers. Therefore, Durnin's equation could be used to assess percentage body fat in elite sport climbers if more accurate methods are not available. The generalizability of the results is limited by the fact that the sample was not selected at random.  相似文献   

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