Relationship of handgrip strength with anthropometric and body composition variables in prepubertal children

The purpose of the present study was to examine the relationship of handgrip strength with basic anthropometric variables, hand anthropometric variables, total body and hand composition, total body and hand bone mineral density (BMD) and bone mineral content (BMC) in prepubertal children aged between 8 and 11 years (n=64, 27 boys, 37 girls). Height and body mass were measured and body mass index (BMI kg/m²) was calculated. Biceps and triceps skinfolds, arm relaxed, arm flexed, forearm and wrist girths, acromiale-radiale, radiale-stylion-radiale and midstylion-dactylion length and humerus breadth were measured. Specific hand anthropometric variables according to Visnapuu and Jürimäe [2007. Handgrip strength and hand dimensions in young handball and basketball players. J. Strength Cond. Res. 21, 923-929] were used. Five fingers’ spans, fingers’ lengths and perimeters of the hand were measured. Total body and right-hand fat percentage, fat mass and lean mass (LBM) were measured by dual-energy X-ray absorptiometry (DXA). Right-hand BMC and BMD were analysed from the bone variables. Maximal handgrip strength of the right hand was measured with the hand dynamometer. Stepwise multiple regression analysis indicated that the most important predictive value from the basic anthropometric variables was body height, explaining 76.1% (R²×100), 40.7% and 50.6% of the handgrip strength in boys, girls and total group, respectively. Measured skinfold thicknesses and breadths were not related to handgrip strength in any group. Forearm girths significantly predicted handgrip strength in boys (30.8%), girls (43.4%) and total group (43.4%). As a rule, handgrip strength was more dependent on the anthropometric and body composition variables in boys than girls. It was concluded that body height, forearm girth, midstylion-dactylion and acromiale-radiale length and hand LBM and BMC are the most limiting factors influencing handgrip strength in prepubertal children.     

Muscular strength and jumping performance relationships in young women athletes

The relationships between muscular strength and vertical jumping performance were examined in young women (14-19 years) track and field jumpers (n = 20) and volleyball players (n = 21). The knee extensor muscular strength measured at 9 knee angles was correlated with jumping height and peak power at the squat (SJ) and the countermovement (CMJ) vertical jump tests. Pearson product coefficient of correlation was used to test the significance of these relationships (p 0.80). Specifically, in the volleyball players, the strong relationships were noted for muscular strength at the knee angle range of 40 degrees to 90 degrees and CMJ jumping height as well as SJ peak power. Results indicate the dissimilarity in the relationships between the knee extensor muscular strength and jumping performance in the young female track and field jumpers and volleyball players. In addition, it appears that the measure selected to evaluate jumping performance alters the correlational results.     

Anthropometric and performance variables discriminating elite American junior men weightlifters

The purpose of this study is to identify physical and performance variables that discriminate elite American junior-aged men weightlifters from nonelite performers. Using a cross-sectional design, multiple discriminant analysis was used to determine field tests identifying elite male junior weightlifters. Young men who were participants (n = 115) at the Junior National and Junior Olympics Weightlifting Championships volunteered as subjects (mean +/- SD age = 14.8 +/- 2.3 years). Elite weightlifters (n = 20) were identified as the top 17.5% of national-level competitors when weightlifting performances were adjusted for body mass using the Sinclair equation. All other weightlifters were classified as nonelite (n = 95). Test batteries were performed immediately upon completion of a national-level weightlifting competition. Variables measured included easily-administered field tests of physical dimensions and body composition, muscular strength and power, flexibility, and gross motor control. The resulting regression equations correctly classified 84.35% of the weightlifters as elite or nonelite. Five variables significantly contributed to the discriminant analysis (Wilks Lambda = 0.6637392, chi(2) = 44.880, df = 5, p < 0.0001, adjusted R(2) = 0.67). Body mass index accounted for 23.13% of the total variance, followed by vertical jump (22.78%), relative fat (18.09%), grip strength (14.43%), and torso angle during an overhead squat (0.92%). The use of these 5 easily administered field tests is potentially useful as a screening tool for elite American junior men weightlifters.     

Acute effect of whole-body vibration on sprint and jumping performance in elite skeleton athletes

The winter sliding sport known as skeleton requires athletes to produce a maximal sprint followed by high speed sliding down a bobsled track. Athletes are required to complete the course twice in 1 hour and total time for the 2 runs determines overall ranking. The purpose of this investigation was to examine the effect of whole-body vibration (WBV) on lower body power to explore the utility of WBV as an ergogenic aid for skeleton competition. Elite skeleton athletes (1 male and 6 females) completed an unloaded squat jump (SQJ) immediately followed by 2 countermovement jumps (CMJs) and a maximal 30-m sprint before and after WBV or no vibration (CON) using a crossover design. The second 30-m sprint was slower following both CON (1.4% decrement; p = 0.05) and WBV (0.7% decrement; p = 0.03). Mean vertical velocity was maintained following WBV in the SQJ but decreased following CON (p = 0.03). There was a trend for athletes to commence the SQJ from a higher starting stance post-WBV compared to CON (p = 0.08). WBV decreased total vertical distance traveled compared to CON in the SQJ (p = 0.006). WBV had little effect on peak velocity, jump height, dip, and peak acceleration or any CMJ parameters. When sprint athletes' warm up and perform maximal jumps and a 30-m sprint with 15-20 minutes of recovery before repeating the sequence, the second series of performances tend to be compromised. However, when WBV is used before the second series of efforts, some aspects of maximal jumping and sprinting appear to be influenced in a beneficial manner. Further research is required to explore whether WBV can improve the second sprint for athletes in actual competition and/or what sort of WBV protocol is optimal for these populations.     

Upper-body anthropometric and strength measures and their relationship to start time in elite luge athletes

Start time has been shown to be a significant predictor of overall performance in the sport of luge. The starting motion in luge has been described as an explosive upper-body movement that requires significant technique and skill to perfect. This study aims to investigate upper-body factors that may relate to start time in luge. Twenty-two subjects participated in the study as part of their normal off-season training. Each subject had a minimum of 3 years' experience in the sport of luge, and at the time was a member of a U.S. Luge National Team. Subjects completed a 1 repetition maximum (1RM) in the bench press (BP), prone row (PR), and weighted pull-up (WP). Anthropometric distances were taken measuring finger-tip span (FS), biacromial breadth (BB), acromio-radial length, acromio-olecranon length (AO), hand length, and sitting cervical height. Subjects were divided into 2 groups based on which U.S. Luge National team they were currently a member of, Senior National (SN, n = 13) and Junior National (JN, n = 9). A Pearson product-moment correlation coefficient showed several significant (p ≤ 0.05) relationships between upper-body variables and start time among the groups. The BP and PR 1RM were shown to have a significant relationship in both groups. Among the anthropometric variables, AO was also significant in both groups. The WP, FS, BB, and height were all shown to have a significant relationship with start time in the SN group, but not in the JN group. These results suggest that as luge athletes become more efficient in the starting technique, outside factors such as upper-body strength and anthropometric measures play a larger role in performance.     

Training leading to repetition failure enhances bench press strength gains in elite junior athletes

The purpose of this study was to investigate the importance of training leading to repetition failure in the performance of 2 different tests: 6 repetition maximum (6RM) bench press strength and 40-kg bench throw power in elite junior athletes. Subjects were 26 elite junior male basketball players (n = 12; age = 18.6 +/- 0.3 years; height = 202.0 +/- 11.6 cm; mass = 97.0 +/- 12.9 kg; mean +/- SD) and soccer players (n = 14; age = 17.4 +/- 0.5 years; height = 179.0 +/- 7.0 cm; mass = 75.0 +/- 7.1 kg) with a history of greater than 6 months' strength training. Subjects were initially tested twice for 6RM bench press mass and 40-kg Smith machine bench throw power output (in watts) to establish retest reliability. Subjects then undertook bench press training with 3 sessions per week for 6 weeks, using equal volume programs (24 repetitions x 80-105% 6RM in 13 minutes 20 seconds). Subjects were assigned to one of two experimental groups designed either to elicit repetition failure with 4 sets of 6 repetitions every 260 seconds (RF(4 x 6)) or allow all repetitions to be completed with 8 sets of 3 repetitions every 113 seconds (NF(8 x 3)). The RF(4 x 6) treatment elicited substantial increases in strength (7.3 +/- 2.4 kg, +9.5%, p < 0.001) and power (40.8 +/- 24.1 W, +10.6%, p < 0.001), while the NF(8 x 3) group elicited 3.6 +/- 3.0 kg (+5.0%, p < 0.005) and 25 +/- 19.0 W increases (+6.8%, p < 0.001). The improvements in the RF(4 x 6) group were greater than those in the repetition rest group for both strength (p < 0.005) and power (p < 0.05). Bench press training that leads to repetition failure induces greater strength gains than nonfailure training in the bench press exercise for elite junior team sport athletes.     

Plasma zinc, copper, leptin, and body composition are associated in elite female judo athletes

This study evaluated levels of plasma zinc, copper, and leptin, body composition, and their relationship in nine elite female judo athletes under two different training conditions. Body composition and biochemical measurements (hematological indexes, plasma zinc, plasma copper, and plasma leptin) were analyzed 24 h after intense training and following a 5-d period without training (no-training). Plasma leptin and plasma zinc increased with no-training. Plasma zinc correlated negatively with percent fat mass (r=−0.62; r=0.05) and positively with plasma leptin (r=0.83; p=0.002) in the no-training condition Plasma copper did not change during the study and correlated positively with plasma leptin (r=0.66; p=0.05) and with percent fat mass (r=0.80; p=0.007) after training. Percent fat mass was associated negatively with plasma zinc (r=−0.62; p=0.05) in the no-training condition. Moreover percent fat mass was negatively associated with the Zn/Cu plasma ratio under both training conditions (r<−0.78, p<0.001). These results are consistent with the possible function of zinc as a lipid-mobilizing factor and of copper as a limiting factor in energy metabolism.     

Relative importance of strength, power, and anthropometric measures to jump performance of elite volleyball players

The purpose of this investigation was to examine the potential strength, power, and anthropometric contributors to vertical jump performances that are considered specific to volleyball success: the spike jump (SPJ) and counter-movement vertical jump (CMVJ). To assess the relationship among strength, power, and anthropometric variables with CMVJ and SPJ, a correlation and regression analysis was performed. In addition, a comparison of strength, power, and anthropometric differences between the seven best subjects and the seven worst athletes on the CMVJ test and SPJ test was performed. When expressed as body mass relative measures, moderate correlations (0.53-0.65; p < or = 0.01) were observed between the 1RM measures and both relative CMVJ and relative SPJ. Very strong correlations were observed between relative (absolute height-standing reach height) depth jump performance and relative SPJ (0.85; p < or = 0.01) and relative CMVJ (0.93; p 相似文献   

Cranial variables as predictors of hominine body mass

Body mass is a key variable in investigating the evolutionary biology of the hominines (Australopithecus, Paranthropus, and Homo). It is not only closely related to life-history parameters but also provides a necessary baseline for studies of encephalization or megadonty. Body mass estimates are normally based on the postcranial skeleton. However, the majority of hominid fossils are cranio-dental remains that are unassociated with postcranial material. Only rarely can postcranial material be linked with craniodentally defined hominid taxa. This study responds to this problem by evaluating body mass estimates based on 15 cranial variables to determine whether they compare in reliability with estimates determined from postcranial variables. Results establish that some cranial variables, and particularly orbital area, orbital height, and biporionic breadth, are nearly as good mass predictors for hominoids as are some of the best postcranial predictors. For the hominines in particular, orbital height is the cranial variable which produces body mass estimates that are most in line with postcranially generated estimates. Both orbital area and biporionic breadth scale differently in the hominines than they do in the other hominoids. This difference in scaling results in unusually large estimates of body mass based on these variables for the larger-sized hominines, although the three cranial variables produce equivalent predicted masses for the smaller-bodied hominines. © 1994 Wiley-Liss, Inc.     

Selected anthropometric variables and aerobic fitness as predictors of cardiovascular disease risk in children

The aim of this study was to assess the suitability of body mass index, waist circumference, waist-to-height ratio and aerobic fitness as predictors of cardiovascular risk factor clustering in children. A cross-sectional study was conducted with 290 school boys and girls from 6 to 10 years old, randomly selected. Blood was collected after a 12-hour fasting period. Blood pressure, waist circumference (WC), height and weight were evaluated according to international standards. Aerobic fitness (AF) was assessed by the 20-metre shuttle-run test. Clustering was considered when three of these factors were present: high systolic or diastolic blood pressure, high low-density lipoprotein (LDL) cholesterol, high triglycerides, high plasma glucose, high insulin concentrations and low high-density lipoprotein (HDL) cholesterol. A ROC curve identified the cut-off points of body mass index (BMI), WC, waist-to-height ratio (WHtR) and AF as predictors of risk factor clustering. BMI, WC and WHR resulted in significant areas under the ROC curves, which was not observed for AF. The anthropometric variables were good predictors of cardiovascular risk factor clustering in both sexes, whereas aerobic fitness should not be used to identify cardiovascular risk factor clustering in these children.     

Anthropometric and strength variables to predict freestyle performance times in elite master swimmers

The aims of this study were to determine in elite master swimmers of both genders whether, using anthropometric variables and the hand grip strength measure, it was possible to predict freestyle performance time, whether the considered predictors were related similarly to different events (50, 100, 200, 400, 800 m), and whether they were the same in male and female master swimmers. The relationships between performance times and age, body mass, height, arm length, forearm length, forearm muscle volume, and hand grip strength were examined in 135 elite master swimmers. Pearson's simple correlation coefficients were calculated and then prediction equations were developed. Age, height, and hand grip strength were the best predictors in short-distance events, whereas only age and height were predictors in middle- and long-distance events. The corresponding coefficient of determination (R) of performance times were 0.84 in the 50-m event, 0.73 in the 100-m event, 0.75 in the 200-m event, 0.66 in the 400-m event, and 0.63 in the 800-m event. These regression equations were then cross-validated in a control group of 126 nonelite, age-matched swimmers, obtaining significant and good correlations for all distances (range, r = 0.67 and 0.83; p < 0.01), indicating that predictors are valid in an extended sample of master swimmers. Differences between sexes were not found in 50-m event, but were present in all other events. These models might be useful to determine individual performance times by contributing to improving the individual's training program and the selection of master swimmers. Coaches could have better accuracy in determining whether an athlete needs a strength training program in order to optimize performance time.     

Explosive strength deficit as a predictor of vertical jumping performance

Currently, variables predictive of vertical jumping performance can account for only part of its total variability. A potential additional source of variation called explosive strength deficit (ESD) was described in 1995 by Zatsiorsky (Science and Practice of Strength Training. Champaign, IL: Human Kinetics, 1995. pp. 34-35.). ESD is determined by measuring the maximum force generated under ideal circumstances (F(mm)) and under task-relevant conditions (F(m)). It is calculated as 100(F(mm) - F(m))/F(m). For this study, the following operational definitions were used: F(mm) = squatting peak force at 0.51 m x s(-1); F(m) = squatting peak force at 1.43 m x s(-1). Data were analyzed using forward stepwise multiple regression. Mean ESD for men was 29.7% (SD = 11.7) and for women was 49.3% (SD = 11.2). For men and women, respectively, zero-order correlations for ESD with restricted vertical jumping (RVJ) distance were -0.35 and -0.60, and between ESD and drop vertical jumping (DVJ) distance were -0.20 and -0.63. However, when the previously identified predictors were taken into account, ESD was not a significant predictor (p > 0.05) of either type of jump. Therefore, it was concluded that ESD on the basis of velocity-regulated squats does not augment the explained variance previously established for vertical jumping performance.     

Relationship of jumping and agility performance in female volleyball athletes

Court sports often require more frequent changes of direction (COD) than field sports. Most court sports require 180 degrees turns over a small distance, so COD in such sports might be best evaluated with an agility test involving short sprints and sharp turns. The purposes of this study were to (a) quantify vertical and horizontal force during a COD task, (b) identify possible predictors of court-sport-specific agility performance, and (c) examine performance difference between National Collegiate Athletic Association Division I, II, and III athletes. Twenty-nine collegiate female volleyball players completed a novel agility test, countermovement (CM) and drop jump tests, and an isometric leg extensor test. The number of athletes by division was as follows: I (n = 9), II (n = 11), and III (n = 9). The agility test consisted of 4 5-meter sprints with 3 180 degrees turns, including 1 on a multiaxial force platform so that the kinetic properties of the COD could be identified. One-way analysis of variance revealed that Division I athletes had significantly greater countermovement jump heights than Division III, and the effect size comparisons (Cohen's d) showed large-magnitude differences between Division I and both Divisions II and III for jump height. No other differences in performance variables were noted between divisions, although effect sizes reached moderate values for some comparisons. Regression analysis revealed that CM displacement was a significant predictor of agility performance, explaining approximately 34% of the variance. Vertical force was found to account for much of the total force exerted during the contact phase of the COD task, suggesting that performance in the vertical domain may limit the COD task used herein. This study indicates that individuals with greater CM performance also have quicker agility times and suggests that training predominantly in the vertical domain may also yield improvements in certain types of agility performance. This may hold true even if such agility performance requires a horizontal component.     

Relative body fat and anthropometric prediction of body density of female athletes

Ninety-one percent (n = 182) of the female members of South Australian representative squads in 14 sports volunteered to act as subjects. Twenty-seven percent of them had represented Australia. The underwater weighing method together with the measurement of residual volume (RV) by helium dilution were used to determine body density (BD); the percent body fat (% BF) was then computed according to Siri. A stepwise multiple regression analysis yielded a correlation coefficient (R) of 0.863 between the criterion (BD) and the best weighted sum of predictors (anthropometric variables): BD (g X cm-3) = 1.14075-0.04959 (log10 sigma triceps, subscapular, supraspinale and calf skinfolds in mm) + 0.00044 (age in decimal years)-0.000612 (waist girth in cm) + 0.000284 (height in cm)-0.000505 (gluteal girth in cm) + 0.000331 (breast girth in cm). Only those predictors which resulted in a statistically significant increase in R (p less than or equal to 0.05) were included. The standard error of estimate of 0.00597 g X cm-3 was equivalent to 2.7% BF at the mean. This equation was shown to be largely population specific. There was a range of 7.6-35.8% of BF and the overall mean 18.5% was significantly lower (p less than 0.001) than that of 23.4% obtained on a moderately active reference sample of similar age (n = 135). If group sizes of only one or two are regarded as too small for meaningful comparison, then the lowest mean of 13.5% was achieved by the long-distance runners (n = 14). The highest averages were registered by the heavyweight rowers (24.2%; n = 7) and soccer players (22.0%; n = 11). The overall average for games players (n = 107) was 19.4%.     

Physiological and anthropometric correlates of tackling ability in junior elite and subelite rugby league players

This study investigated the tackling ability of junior elite and subelite rugby league players, and determined the relationship between selected physiological and anthropometric characteristics and tackling ability in these athletes. Twenty-eight junior elite (mean ± SD age, 16.0 ± 0.2 years) and 13 junior subelite (mean ± SD age, 15.9 ± 0.6 years) rugby league players underwent a standardized 1-on-1 tackling drill in a 10-m grid. Video footage was taken from the rear, side, and front of the defending player. Tackling proficiency was assessed using standardized technical criteria. In addition, all players underwent measurements of standard anthropometry (stature, body mass, and sum of 7 skinfolds), acceleration (10-m sprint), change of direction speed (505 test), and lower body muscular power (vertical jump). Junior elite players had significantly greater (p < 0.05) tackling proficiency than junior subelite players (65.7 ± 12.5 vs. 54.3 ± 16.8%). Junior elite players tended to be taller, heavier, leaner, and have greater acceleration, change of direction speed, and muscular power, than the junior subelite players. The strongest individual correlates of tackling ability were acceleration (r = 0.60, p < 0.001) and lower body muscular power (r = 0.38, p < 0.05). When multiple linear regression analysis was performed to determine which of the physiological and anthropometric characteristics predicted tackling ability, fast acceleration was the only variable that contributed significantly (r2 = 0.24, p < 0.01) to the predictive model. These findings demonstrate that fast acceleration, and to a lesser extent, lower body muscular power contribute to effective tackling ability in junior rugby league players. From a practical perspective, strength and conditioning coaches should emphasize the development of acceleration and lower body muscular power qualities to improve tackling ability in junior rugby league players.     

Neuromuscular, anaerobic, and aerobic performance characteristics of elite power athletes

Various aspects of neuromuscular, anaerobic, and aerobic performance capacity were investigated in four powerlifters, seven bodybuilders, and three wrestlers with a history of specific training for several years. The data (means +/- SD) showed that the three subject groups possessed similar values for maximal isometric force per unit bodyweight (50.7 +/- 9.6, 49.3 +/- 4.1, and 49.3 +/- 10.9 N/kg, respectively). However, significant (P less than 0.05) differences were observed in the times for isometric force production, so that e.g., times to produce a 30% force level were shorter for the wrestlers and bodybuilders (28.3 +/- 3.1 and 26.4 +/- 6.6 ms) than that (53.3 +/- 23.7 ms) for the powerlifters. Utilization of elastic energy by the wrestlers was significantly (P less than 0.05) better than that of the other two subject groups, as judged from differences between the counter-movement and squat jumps at 0, 40, and 100 kg's loads. No differences were observed between the groups in anaerobic power in a 1-min maximal test, but the values for VO2 max were higher (P less than 0.05) among the wrestlers and bodybuilders (57.8 +/- 6.6 and 50.8 +/- 6.8 ml X kg-1 X min-1) as compared to the powerlifters (41.9 +/- 7.2 ml X kg-1 X min-1). Within the limitations of the subject sample, no differences of a statistical significancy were observed between the groups in fibre distribution, fibre areas, or the area ratio of fast (FT) and slow (ST) twitch fibres in vastus lateralis.(ABSTRACT TRUNCATED AT 250 WORDS)     

Endurance training and sprint performance in elite junior cross-country skiers

The purpose of the present study was to investigate the relationship between aerobic characteristics and sprint skiing performance, and the effects of high-intensity endurance training on sprint skiing performance and aerobic characteristics. Ten male and 5 female elite junior cross-country skiers performed an 8-week intervention training period. The intervention group (IG, n = 7) increased the volume of high-intensity endurance training performed in level terrain, whereas the control group (CG, n = 8) continued their baseline training. Before and after the intervention period, the skiers were tested for 1.5-km time-trial performance on roller skis outdoors in the skating technique. Maximal oxygen uptake (VO?max) and oxygen uptake at the ventilatory threshold (VO?VT) were measured during treadmill running. VO?max and VO?VT were closely related to sprint performance (r = ~0.75, both p < 0.008). The IG improved sprint performance, VO?max, and VO?VT from pre to posttesting and improved sprint performance and VO?VT when compared to the CG (all p < 0.01). This study shows a close relationship between aerobic power and sprint performance in cross-country skiing and highlights the positive effects of high-intensity endurance training in level terrain.     

Influence of performance level on anaerobic power and body composition in elite male judoists

This study examined the relationship between 30-second anaerobic power and body composition by performance level in elite Judoists. During a 3-month period, 10 male Korean Judo national team athletes (NT), 26 male university varsity team athletes (VT), and 28 male junior varsity team athletes (JT) were assessed for 30-second anaerobic power and body composition at the Youngin University. Anaerobic power was measured using a 30-second Wingate test. Body composition was assessed via bioelectric impedance analysis in standardized conditions using BioSpace (Korean)-specific prediction formulas. All testing occurred at the beginning of the winter nonseason period but excluded a brief weight-loss period before the competition phase. Anaerobic power measures were significantly greater (p < 0.05) in NT and VT than in JT. Fat-free mass (FFM), muscle mass (MM), and total body water in JT were also greater than in VT and JT (p < 0.05). Muscle mass in VT was significantly lower than in NT (p < 0.05). Fat-free mass in NT was strongly correlated to mean and peak anaerobic power (r = 0.77, p = 0.009; r = 0.87, p < 0.001, respectively). Varsity team athletes also indicated a moderate association between FFM and peak and mean anaerobic power (r = 0.63, p < 0.001; r = 0.48, p = 0.013, respectively). However, relationship between FFM and anaerobic power was not statistically significantly correlated in JT (r = 0.14, p = 0.470; r = 0.23, p = 0.232, separately). In conclusion, our data indicated that anaerobic power is closely correlated with increase in FFM and MM and was different dependent among performance levels. Further research in the field is warranted to elucidate the Judo-specific relationship between FFM and performance.