首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 31 毫秒
1.
We aimed to assess the agreement of a commercially available bioelectrical impedance analysis (BIA) device in measuring changes in fat, lean and bone mass over a 10-week lifestyle intervention, with dual energy X-ray absorptiometry (DXA) as reference. A sample of 136 volunteers (18–66 years) underwent a physical activity intervention to enhance lean mass and reduce fat mass. BIA (Tanita BC545) and DXA (Hologic Explorer) measures of whole-body composition were taken at baseline and at the end of the intervention. After an average of 74 ± 18 days intervention, DXA showed significant changes in 2 of 3 outcome variables: reduced fat mass of 0.802 ± 1.092 kg (P < 0.001), increased lean mass of 0.477 ± 0.966 kg (P < 0.001); minor non-significant increase of 0.007 ± 0.041 kg of bone mass (P = 0.052). The respective changes in BIA measures were a significant reduction of 0.486 ± 1.539 kg fat (P < 0.001), but non-significant increases of 0.084 ± 1.201 kg lean mass (P = 0.425), and 0.014 ± 0.091 kg bone (P = 0.074). Significant, but moderately weak, correlations were seen in absolute mass changes between DXA and BIA: 0.511 (fat), 0.362 (lean) and 0.172 (bone). Compared to DXA, BIA demonstrated mediocre agreement to changes in fat mass, but poor agreement to lean mass changes. BIA significantly underestimated the magnitude of changes in fat and lean mass compared to DXA.  相似文献   

2.
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   

3.
Introduction: There is a large variety of body fat (BF) measurements, which differ in validity and reliability. The aim of this study was to measure subcutaneous adipose tissue (SAT) using ultrasound (US) in highly trained junior rowers in a field setting, establish fat patterning profiles, and compare the profiles between male and female athletes. Skinfold thickness (SKF) measurements were also taken and compared to US measurements. Methods: Sixteen athletes participated. US measurements were taken at eight sites and reported as a sum of SAT (D): DExcl (without embedded structures) and DIncl (including embedded structures). SKF was measured at three sites and reported as a sum of adipose tissue thickness (SUMSKF). Results: Mean SAT thickness (DIncl) was 27.6?±?12.4?mm for males and 65.5?±?11.8?mm for females. Females had significantly more embedded structures than males (P?=?.016). Significant correlations were found (P?<?.001, r?=?0.92) comparing SUMSKF to DIncl and between SKF and US measurements at the thigh site (P?<?.001, r?=?0.86). Conclusion: US is a suitable tool to measure BF in the field testing of athletes and enables measurements of SAT with an accuracy and reliability not reached before. The sum of thicknesses (DIncl or DExcl) can be used to represent subcutaneous fat based on accurate measurements of uncompressed SAT thicknesses.  相似文献   

4.
Purpose: To determine the effect of limb selection (upper/lower), cuff width (small (6?cm)/medium (13?cm) upper; medium/large (18?cm) lower) and anthropometry on arterial occlusion pressure (AOP) in ischemic preconditioning (IPC). Methods: Twenty athletes (10 females and 10 males) had surface anthropometry and dual x-ray absorptiometry (DXA) assessments before using Doppler ultrasound to confirm AOP for each limb. Subsequently, 5?min of occlusion occurred, with near-infrared spectroscopy (NIRS) measuring muscle oxygenation changes. Resultant AOP was compared between sexes, limbs and cuff sizes using linear regression models. Results: Mean AOP was higher in the lower limbs than the upper limbs (161?±?18 vs. 133?±?12?mm?Hg; p?p?p?=?.222). Sex and resting systolic blood pressure (SBP) accounted for 77% (small cuff) to 83% (medium cuff) of variance in AOP for upper limbs, and 61% (medium cuff) to 63% (large cuff) in lower limbs. Including anthropometry accounted for 82% (small cuff) to 89% (medium cuff) and 78% (medium cuff) to 79% (large cuff) of variance for upper and lower limbs, respectively. Adding DXA variables improved the explained variance up to 83% (small cuff) to 91% (medium cuff) and 79% (medium cuff) to 87% (large cuff) for upper and lower limbs, respectively. NIRS data showed significantly greater tissue oxygenation changes in upper versus lower limbs. Conclusions: The AOP in athletes is dependent on limb occluded, sex, SBP, limb and cuff size, and body composition.  相似文献   

5.
Abstract

This study investigated the participation and performance trends as well as the age and gender interaction at the Olympic distance ‘Zürich Triathlon’ (1.5?km swim, 40?km cycle and 10?km run) from 2000 to 2010 in 7,939 total finishers (1,666 females and 6,273 males). Female triathletes aged from 40 to 54 years significantly (P?<?0.05) increased their participation while the participation of younger females and males remained stable. Males of 50–54 years of age and females of 45–49 years of age improved their total race time. For elite top five overall triathletes, mean gender differences in swimming, cycling, running and overall race time were 15.2?±?4.6%, 13.4?±?2.3%, 17.1?±?2.5%, and 14.8?±?1.8%, respectively. For both elite and age group athletes, the gender difference in cycling time was significantly (P?<0.001) lower than for swimming and running. The gender difference in overall Olympic distance triathlon performance increased after the age of 35 years, which appeared earlier compared to long distance triathlon as suggested by previous studies. Future investigations should compare gender difference in performance for different endurance events across age to confirm a possible effect of exercise duration on gender difference with advancing age.  相似文献   

6.
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 cm(2)). 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 cm(2)), 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   

7.
Abstract

This study determined the precision of pencil and fan beam dual-energy X-ray absorptiometry (DXA) devices for assessing body composition in professional Australian Football players. Thirty-six professional Australian Football players, in two groups (fan DXA, N = 22; pencil DXA, N = 25), underwent two consecutive DXA scans. A whole body phantom with known values for fat mass, bone mineral content and fat-free soft tissue mass was also used to validate each DXA device. Additionally, the criterion phantom was scanned 20 times by each DXA to assess reliability. Test–retest reliability of DXA anthropometric measures were derived from repeated fan and pencil DXA scans. Fat-free soft tissue mass and bone mineral content from both DXA units showed strong correlations with, and trivial differences to, the criterion phantom values. Fat mass from both DXA showed moderate correlations with criterion measures (pencil: r = 0.64; fan: r = 0.67) and moderate differences with the criterion value. The limits of agreement were similar for both fan beam DXA and pencil beam DXA (fan: fat-free soft tissue mass = ?1650 ± 179 g, fat mass = ?357 ± 316 g, bone mineral content = 289 ± 122 g; pencil: fat-free soft tissue mass = ?1701 ± 257 g, fat mass = ?359 ± 326 g, bone mineral content = 177 ± 117 g). DXA also showed excellent precision for bone mineral content (coefficient of variation (%CV) fan = 0.6%; pencil = 1.5%) and fat-free soft tissue mass (%CV fan = 0.3%; pencil = 0.5%) and acceptable reliability for fat measures (%CV fan: fat mass = 2.5%, percent body fat = 2.5%; pencil: fat mass = 5.9%, percent body fat = 5.7%). Both DXA provide precise measures of fat-free soft tissue mass and bone mineral content in lean Australian Football players. DXA-derived fat-free soft tissue mass and bone mineral content are suitable for assessing body composition in lean team sport athletes.  相似文献   

8.
This study examined the effects of different work?–?rest durations during 40?min intermittent treadmill exercise and subsequent running performance. Eight males (mean?±?s: age 24.3?±?2.0 years, body mass 79.4?±?7.0?kg, height 1.77?±?0.05?m) undertook intermittent exercise involving repeated sprints at 120% of the speed at which maximal oxygen uptake (v-[Vdot]O2max) was attained with passive recovery between each one. The work?–?rest ratio was constant at 1:1.5 with trials involving short (6:9?s), medium (12:18?s) or long (24:36?s) work?–?rest durations. Each trial was followed by a performance run to volitional exhaustion at 150% v-[Vdot]O2max. After 40?min, mean exercise intensity was greater during the long (68.4?±?9.3%) than the short work?–?rest trial (54.9?±?8.1% [Vdot]O2max; P?<?0.05). Blood lactate concentration at 10?min was higher in the long and medium than in the short work?–?rest trial (6.1?±?0.8, 5.2?±?0.9, 4.5?±?1.3?mmol?·?l?1, respectively; P?<?0.05). The respiratory exchange ratio was consistently higher during the long than during the medium and short work?–?rest trials (P <?0.05). Plasma glucose concentration was higher in the long and medium than in the short work?–?rest trial after 40?min of exercise (5.6?±?0.1, 6.6?±?0.2 and 5.3?±?0.5?mmol?·?l?1, respectively; P?<?0.05). No differences were observed between trials for performance time (72.7?±?14.9, 63.2?±?13.2, 57.6?±?13.5?s for the short, medium and long work?–?rest trial, respectively; P = 0.17), although a relationship between performance time and 40?min plasma glucose was observed (P?<?0.05). The results show that 40?min of intermittent exercise involving long and medium work?–?rest durations elicits greater physiological strain and carbohydrate utilization than the same amount of intermittent exercise undertaken with a short work?–?rest duration.  相似文献   

9.
Older adults are a priority within policy designed to facilitate healthy lifestyles through physical activities. Golden Goal is a pilot programme of physical activity-led health improvement for older adults, 55?years and older. Activities were delivered at Burton Albion Football Club. Sessions involved weekly moderate to vigorous intensity exercise sessions including exer-gaming (exercise-orientated video-games), indoor bowls, cricket, new age curling, walking football, and traditional board games and skittles. Secondary analysis of data collected through the original programme evaluation of Golden Goal investigated the impact of the intervention on participants. Older adults completed self-reports for demographics, health screening/complications and quality of life. Attendees, n?=?23 males (42.6%) and n?=?31 females (57.4%) with a mean age of 69.38 (±5.87) (n?=?40), ranging from 55–85?years took part. The mean attendance was 7.73 (±3.12) sessions for all participants, (n?=?51). Older adults with two or more health complications (n?=?22, 42.3%) attended fewer sessions on average (6.91?±?3.322) compared to those reporting less than two health complications (8.65?±?2.694). Self-rated health was higher for women (87.32?±?9.573) vs. men (80.16?±?18.557), although this was not statistically significant (U?=?223.500, p?=?0.350). Results support the potential of football-led health interventions for recruiting older adults, including those reporting health problems.  相似文献   

10.
Attenuated performance during intense exercise with limited endogenous carbohydrate (CHO) is well documented. Therefore, this study examined whether caffeine (CAF) mouth rinsing would augment performance during repeated sprint cycling in participants with reduced endogenous CHO. Eight recreationally active males (aged 23?±?2?yr, body mass 84?±?4?kg, stature 178?±?7?cm) participated in this randomized, single-blind, repeated-measures crossover investigation. Following familiarization, participants attended two separate evening glycogen depletion sessions. The following morning, participants completed five, 6?s sprints on a cycle ergometer (separated by 24?s active recovery), with mouth rinsing either (1) a placebo solution or (2) a 2% CAF solution. During a fifth visit, participants completed the sprints without prior glycogen depletion. Repeated-measures ANOVA identified significant main effect of condition (CAF, placebo, and control [P?P?P?P?P?P?相似文献   

11.
  相似文献   

12.
The primary purpose of this study was to investigate the accuracy of the DF50 (ImpediMed Ltd, Eight Mile Plains, Queensland, Australia) bioelectrical impedance analysis device using dual-energy x-ray absorptiometry as the criterion in two groups: endurance athletes and power athletes. The secondary purpose was to develop accurate body fat percentage prediction equations for each group based on bioelectrical impedance analysis data and/or the combination of bioelectrical impedance analysis and anthropometric data.

Eighty male athletes (40 elite endurance athletes and 40 were power athletes), age 19–48 with body mass indexes ranging from 18.9 to 37.4 were recruited. Anthropometric measurements were taken. Body composition was assessed by dual-energy x-ray absorptiometry and bioelectrical impedance analysis. An athlete-specific bioelectrical impedance analysis prediction equation was developed by stepwise regression analysis using dual-energy x-ray absorptiometry as the criterion and bioelectrical impedance analysis data and anthropometric measurements as predictor variables.

The DF50 bioelectrical impedance analysis significantly overestimated body fat percentage by 6.4 ± 0.5 in the entire group (p < .001) and in both the endurance group (6.1 ± .6, p < .001) and the power group (6.7 ± 0.7, p < .001). The endurance and power group showed no significant difference in the error of estimation by bioelectrical impedance analysis (p = .554), indicating that bioelectrical impedance analysis has the same error in both groups. The final prediction equation incorporated both anthropometric variables as well as bioelectrical impedance analysis variables and produced an adjusted r2 of .982 and a standard error of the estimate (SEE) of 1.98 for the entire group. This prediction equation used bioelectrical impedance analysis measurements and anthropometric measurements, specifically trunk measurements, to account for trunk size, a common source of error in bioelectrical impedance analysis equations. Follow-up validation studies are necessary to further validate the equations produced.  相似文献   

13.
Abstract

The purpose of this study was to examine the effect of fatiguing exercise on sex-related differences in the function of hamstring and quadriceps muscles at several angular velocities and joint angles. Physically active participants (50 male: 28.7?±?4.5y, 1.82?±?0.07 m, 82.3?±?6.87?kg; 50 female: 27.0?±?5.8y, 1.61?±?0.08 m, 68.75?±?9.24?kg) carried out an isokinetic assessment to determine concentric and eccentric torques during knee extension and flexion actions at three different angular velocities (60/180/300°/s). The H/QFUNCT was calculated using peak torque (PT) values at 3 different joint-angle-specific (15°, 30° and 45° of knee flexion). A repeated measures analysis of variance (ANOVA) was used to compare within group results. Between group comparisons of sex-related differences were assessed by independent T-tests. Fatiguing exercise in males resulted in a decrease in H/QFUNCT ratios for each angle of knee flexion at both 60°/s and 300°/s angular velocities (p?<?0.05). In females, significant decreases in H/QFUNCT ratios were observed following fatiguing exercise for each angle of knee flexion and angular velocity (p?<?0.01). Significant differences in H/QFUNCT ratios following fatiguing exercise were evident between males and females at each joint angle and angular velocity (p?<?0.01). These findings indicate sex related differences in H/QFUNCT ratios following fatiguing exercise. Females have greater reductions in torque and H/QFUNCT ratios following fatigue than their male counterparts. This potentially exposes females to higher risks of injury, particularly when fatigued. Practitioners should attend to the imbalance in fatigue resistance of hamstring and quadriceps function, particularly in female athletes.  相似文献   

14.
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   

15.
This study compared knee angle-specific neuromuscular adaptations after two low-volume isometric leg press complex training programmes performed at different muscle lengths. Fifteen young males were divided into two groups and trained three times per week for 6 weeks. One group (n?=?8) performed 5–7 sets of 3 s maximum isometric leg press exercise, with 4?min recovery, with knee angle at 85°?±?2° (longer muscle-tendon unit length; L-MTU). The other group (n?=?7) performed the same isometric training at a knee angle of 145°?±?2° (180°?=?full extension; shorter muscle-tendon unit length; S-MTU). During the recovery after each set of isometric exercise, participants performed two CMJ every minute, as a form of complex training. Maximum isometric force (MIF) and rate of force development (RFD) were measured over a wide range of knee angles. Countermovement jump (CMJ) performance and maximum half-squat strength (1RM) were also assessed. Training at S-MTU induced a large increase of MIF (22–58%, p?p?p?=?0.001). In contrast, training at L-MTU, resulted in a moderate and similar (≈12.3%, p?=?0.028) improvement of force at all knee angles. CMJ performance and 1RM were equally increased in both groups after training by 10.4%?±?8.3% and 7.8%?±?4.7% (p?相似文献   

16.
Purpose: Conventional Bioelectrical Impedance Analysis (BIA) or Bioelectrical Impedance Vector Analysis (BIVA) can provide direct evaluations of body composition. The purpose of this study was to evaluate lean and fat mass (FM), and hydration of children involved in daily competitive sports. Methods: 190 non-athletic [8.2–10.5 years] and 29 competitive children [8.0–10.5 years] were enrolled. They were evaluated: at baseline (t0), 6 months (t1) and one year (t2). Anthropometric, BIA and BIVA, lean and FM, and hydration evaluations were performed. Results: Resistance (R/h) and reactance (Xc/h) were lower at t0 in competitive individuals when compared to controls. Xc/h (+3.28) significantly increases in competitive when compared to non-competitive individuals (+0.66, p for difference: 0.011), while phase angle (PA) was lower at t0 (5.72 vs. 6.17, p?<?.001) and after 6 months (p?=?.001). Total body water adjusted for height (TBW/h) significantly increased only in non-athletes (+0.50?±?0.13, p?<?.001) between t0 and t1. At t1, extracellular water (ECW) significantly decreased (p?=?.026) in the two groups: ?0.45?±?0.19% in non-competitive, ?1.63?±?0.49% in competitive subjects, while intracellular water (ICW) increased. At one-year follow-up (t2), there were no statistically significant differences in R/h, Xc/h and PA in competitive individuals when compared to baseline and t1. Furthermore, we observed at t2 that hours/week of training, age, male gender and body mass index can influence FFM/h and FM/h in both competitive and non-competitive subjects. In particular, a direct correlation was for hours/week and FFM/h, inverse for hours/week and FM/h. Conclusions: Body mass index does not allow evaluating differences in lean body mass and FM between athletes and non-athletes. BIA and BIVA can give more reliable details about body composition differences in competitive adolescents and non-competitive, outlining a progressive decline in ECW and increase in ICW without affecting TBW composition of athletes.  相似文献   

17.
The purpose of this study was to examine the test–retest reliability and construct validity of three age-adapted Yo-Yo intermittent tests in football players aged 9–16 years (n?=?70) and in age-matched non-sports active boys (n?=?72). Within 7 days, each participant performed two repetitions of an age-related intensity-adapted Yo-Yo intermittent test, i.e. the Yo-Yo intermittent recovery level 1 children's test for 9- to 11-year-olds; the Yo-Yo intermittent endurance level 1 for 12- to 13-year-olds and the Yo-Yo intermittent endurance level 2 test for 14- to 16-year-olds. Peak heart rate (HRpeak) was determined for all tests. The distance covered in the tests was 57% (1098?±?680 vs. 700?±?272?m), 119% (2325?±?778 vs. 1062?±?285?m) and 238% (1743?±?460 vs. 515?±?113?m) higher (p?≤?.016), respectively for football-trained than for non-sports active boys aged 9–11, 12–13 and 14–16 years. The typical errors of measurement for Yo-Yo distance, expressed as a percentage of the coefficient of variation (confidence interval), were 11.1% (9.0–14.7%), 10.1% (8.1–13.7%) and 8.5% (6.7–11.7%) for football players aged 9–11, 12–13 and 14–16 years, respectively, with corresponding values of 9.3% (7.4–12.8%), 10.2% (8.1–14.0%) and 8.5% (6.8–11.3%) for non-sports active boys. Intraclass correlation coefficient values for test–retest were excellent in both groups (range: 0.844–0.981). Relative HRpeak did not differ significantly between the groups in test and retest. In conclusion, Yo-Yo intermittent test performances and HRpeak are reliable for 9- to 16-year-old footballers and non-sports active boys. Additionally, performances of the three Yo-Yo tests were seemingly better for football-trained than for non-sports active boys, providing evidence of construct validity.  相似文献   

18.
The purpose of this study was to examine the effects of external load on vertical ground reaction force, and linear and angular kinematics, during squats. Eight males aged 22.1?±?0.8 years performed maximal concentric squats using loads ranging from 7 to 70% of one-repetition maximum on a force plate while linear barbell velocity and the angular kinematics of the hip, knee and ankle were recorded. Maximum, average and angle-specific values were recorded. The ground reaction force ranged from 1.67?±?0.20 to 3.21?±?0.29 times body weight and increased significantly as external load increased (P?<?0.05). Bar linear velocity ranged from 0.54?±?0.11 to 2.50?±?0.50?m?·?s?1 and decreased significantly with increasing external load (P?<?0.05). Hip, knee and ankle angles at maximum ground reaction force were affected by external load (P?<?0.05). The force?–?barbell velocity curves were fitted using linear models with coefficients (r 2) ranging from 0.59 to 0.96. The results suggest that maximal force exertion during squat exercises is not achieved at the same position of the lower body as external load is increased. In contrast, joint velocity coordination does not change as load is increased. The force?–?velocity relationship was linear and independent from the set of data used for its determination.  相似文献   

19.
The aim of this study was to compare the somatotype and size of elite female basketball players in terms of playing position and team performance. Anthropometry and somatotype data were collected on 168 players from 14 countries before the Women's World Basketball Championship, Australia, 1994. There were 64 guards (mean?±?s: age 25.4?±?3.3 years, height 1.72?±?0.06?m, mass 66.1?±?6.2?kg, somatotype?=?2.9?–?3.9?–?2.6), 57 forwards (age 25.2?±?3.8 years, height 1.81?±?0.06?m, mass 73.3?±?5.9?kg, somatotype?=?2.8?–?3.5?–?3.2) and 47 centres (age 24.1?±?3.1 years, height 1.90?±?0.06?m, mass 82.6?±?8.2?kg, somatotype?=?3.2?–?3.1?–?3.4). Mean somatotypes by position were significantly different (F?=?7.73, P?<?0.01). Guards had greater mesomorphy than centres and less ectomorphy than forwards and centres. When discriminant function analysis was applied to endomorphy, mesomorphy, ectomorphy, age, height and mass, only height, mass and ectomorphy entered (Wilks' λ?=?0.351, F?=?31.40, P?<?0.000), 70% of the variance was accounted for, and 72% of players were correctly classified. In the four top versus four bottom teams, guards were taller and more ectomorphic, forwards were taller, with lower mesomorphy and higher ectomorphy, and centres did not differ. Thus there are some differences in somatotypes by position and team placing, but the combination of height, mass and ectomorphy provide the best differentiation by position.  相似文献   

20.
Abstract

In this study, video and force analysis techniques were used to distinguish between dragon boat paddlers of different ability. Six elite paddlers (three males, three females) and six sub-elite paddlers (two males, four females) were compared during high-intensity paddling (80–90 strokes · min?1). Video filming was conducted for two-dimensional kinematic analysis and an instrumented paddle was used to collect force data. Paddling efficiency, paddle force characteristics, and paddler kinematic variables were measured. Elite paddlers achieved higher paddling efficiency than sub-elite paddlers (elite: 76 ± 4%; sub-elite: 67 ± 10%; P = 0.080). Elite paddlers also showed higher peak force (elite: 16.3 ± 4.8 N · kg?2/3; sub-elite: 11.4 ± 2.6 N · kg?2/3; P = 0.052), average force (elite: 7.9 ± 2.8 N · kg?2/3; sub-elite: 5.5 ± 1.4 N · kg?2/3; P = 0.084), and impulse (elite: 3.0 ± 0.9 (N · s) · kg?2/3; sub-elite: 1.9 ± 0.4 (N · s) · kg?2/3; P = 0.026) than sub-elite paddlers, but these three results should be viewed with caution due to the small sample size and the unequal number of males and females in the two groups. Superior technique and greater strength enable the elite paddlers to achieve higher paddling efficiency. Paddlers use different joint movement patterns to develop propulsion, which are reflected in variations in the force–time curve.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号