Prediction of fat and fat-free mass in male athletes using dual X-ray absorptiometry as the reference method

The ability of bioelectrical impedance analysis and anthropometry to predict fat mass and fat-free mass was compared in a sample of 82 male athletes from a wide variety of sports, using dual-energy X-ray absorptiometry (DXA) as the reference method. The percent fat measured by DXA was 10.9 - 4.9% (mean - s ), and fat mass was predicted with a standard error of the estimate of 1.7 kg for skinfolds and 2.8 kg for bioelectrical impedance analysis (P?0.001). Fat-free mass was predicted with a standard error of the estimate of 1.7 kg for anthropometry and 2.6 kg for bioelectrical impedance analysis (P?0.001). Regression of various individual skinfolds and summed skinfolds, to examine the eff ect of skinfold selection combinations by stepwise regression, produced an optimal fat mass prediction using the thigh and abdominal skinfold sites, and an optimal fat-free mass prediction using the thigh, abdominal and supra-ilium sites. These results suggest that anthropometry off ers a better way of assessing body composition in athletes than bioelectrical impedance analysis. Applying the derived equations to a separate sample of 24 athletes predicted fat and fat-free mass with a total error of 2.3 kg (2.9%) and 2.2 kg (2.7%), respectively. Combining the samples introduced more heterogeneity into the sample (n=106), and the optimal prediction of fat mass used six skinfolds in producing a similar standard error of the estimate (1.7 kg), although this explained a further 4% of the variation in DXA-derived fat. Fat-free mass was predicted best from four skinfolds, although the standard error of the estimate and coefficient of determination were unchanged.     

Variability and progression in competitive performance of Paralympic swimmers

Abstract

Analysis of variability and progression in performance of top athletes between competitions provides information about performance targets that is useful for athletes, practitioners, and researchers. In this study, 724 official finals times were analysed for 120 male and 122 female Paralympic swimmers in the 100-m freestyle event at 15 national and international competitions between 2004 and 2006. Separate analyses were performed for males and females in each of four Paralympic subgroups: S2–S4, S5–S7, S8–S10 (most through least physically impaired), and S11–S13 (most through least visually impaired). Mixed modelling of log-transformed times, with adjustment for mean competition times, was used to estimate variability and progression. Within-swimmer race-to-race variability, expressed as a coefficient of variation, ranged from 1.2% (male S5–S7) to 3.7% (male S2–S4). Swimming performance progressed by approximately 0.5% per year for males and females. Typical variation in mean performance time between competitions was ～1% after adjustment for the ability of the athletes in each competition, and the Paralympic Games was the fastest competition. Thus, taking into account variability, progression, and level of competition, Paralympic swimmers who want to increase substantially their medal prospects should aim for an annual improvement of at least 1–2%.     

The quantification of joint laxity in dancers and gymnasts

The aim of this study was to determine the range of movement in gymnastic and dance populations. Sixty-five participants (41 females, 24 males; mean age 21.4 years) were assessed. The sample included dancers and gymnasts ranging from novice and club standard to international and professional status. Non-specialized physical education students acted as controls. Range of movement was measured at the shoulders, hips, lumbar spine and ankles using a Loebl hydrogoniometer, and inherent joint laxity was assessed using Beighton and coworkers' adaptation of the Carter and Wilkinson 9-point scale. The right and left sides of the body were assessed and measures of active and passive motion were recorded. A graded increase in laxity was observed from controls, through novice gymnasts, to dancers and finally international gymnasts. The greater laxity of females than males was also confirmed. Dancers and gymnasts had a greater passive range of movement in all joints, which was partly inherited and partly acquired. There was a large difference between their active and passive ranges, which appeared to render the joints unstable.     

残奥会运动员文化、职业、奖牌分布的对比分析——以第十三届北京残奥会中、外乒乓球运动员为例

通过数理统计法,访谈法等,对第十三届北京残奥会中、外乒乓球运动员文化、职业、奖牌分布进行对比分析,找出我国残疾人乒乓球队继续发展存在的潜在问题,如训练经费少、赛事组织少,训练时间不能保证、重视程度不够等,对我国残疾人乒乓球队继续发展提出可行的建议,如增加资金支持,加大对残疾人乒乓球运动员的文化教育。拓宽选材的渠道。     

The mechanics of American football cleats on natural grass and infill-type artificial playing surfaces with loads relevant to elite athletes

This study quantified the mechanical interactions of 19 American football cleats with a natural grass and an infill-type artificial surface under loading conditions designed to represent play-relevant manoeuvres of elite athletes. Variation in peak forces and torques was observed across cleats when tested on natural grass (2.8–4.2 kN in translation, 120–174 Nm in rotation). A significant (p < 0.05) relationship was found between the peak force and torque on natural grass. Almost all of the cleats caused shear failure of the natural surface, which generated a divot following a test. This is a force-limiting cleat release mode. In contrast, all but one of the cleat types held fast in the artificial turf, resulting in force and torque limited by the prescribed input load from the test device (nom. 4.8 kN and 200 Nm). Only one cleat pattern, consisting of small deformable nubs, released on the artificial surface and generated force (3.9 kN) comparable to the range observed with natural grass. These findings (1) should inform the design of cleats intended for use on natural and artificial surfaces and (2) suggest a mechanical explanation for a higher lower-limb injury rate in elite athletes playing on artificial surfaces.     

PART III: HUMAN PERFORMANCE

There is limited information on the anthropometry, strength, endurance and flexibility of female rock climbers. The aim of this study was to compare these characteristics in three groups of females: Group 1 comprised 10 elite climbers aged 31.3 ± 5.0 years (mean ± s ) who had led to a standard of ‘hard very severe’; Group 2 consisted of 10 recreational climbers aged 24.1 ± 4.0 years who had led to a standard of ‘;severe’; and Group 3 comprised 10 physically active individuals aged 28.5 ± 5.0 years who had not previously rock-climbed. The tests included finger strength (grip strength, finger strength measured on climbing-specific apparatus), flexibility, bent arm hang and pull-ups. Regression procedures (analysis of covariance) were used to examine the influence of body mass, leg length, height and age. For finger strength, the elite climbers recorded significantly higher values ( P < 0.05) than the recreational climbers and non-climbers (four fingers, right hand: elite 321 ± 18 N, recreational 251 ± 14 N, non-climbers 256 ± 15 N; four fingers, left hand: elite 307 ± 14 N, recreational 248 ± 12 N, non-climbers 243 ± 11 N). For grip strength of the right hand, the elite climbers recorded significantly higher values than the recreational climbers only (elite 338 ± 12 N, recreational 289 ± 10 N, non-climbers 307 ± 11 N). The results suggest that elite climbers have greater finger strength than recreational climbers and non-climbers.     

Effect of the movement speed of resistance training exercises on sprint and strength performance in concurrently training elite junior sprinters

The aim of this study was to determine the effects of 7 weeks of high- and low-velocity resistance training on strength and sprint running performance in nine male elite junior sprint runners (age 19.0 - 1.4 years, best 100 m times 10.89 - 0.21 s; mean - s ). The athletes continued their sprint training throughout the study, but their resistance training programme was replaced by one in which the movement velocities of hip extension and flexion, knee extension and flexion and squat exercises varied according to the loads lifted (i.e. 30-50% and 70-90% of 1-RM in the high- and low-velocity training groups, respectively). There were no between-group differences in hip flexion or extension torque produced at 1.05, 4.74 or 8.42 rad·s -1 , 20 m acceleration or 20 m 'flying' running times, or 1-RM squat lift strength either before or after training. This was despite significant improvements in 20 m acceleration time ( P ? 0.01), squat strength ( P ? 0.05), isokinetic hip flexion torque at 4.74 rad·s -1 and hip extension torque at 1.05 and 4.74 rad·s -1 for the athletes as a whole over the training period. Although velocity-specific strength adaptations have been shown to occur rapidly in untrained and non-concurrently training individuals, the present results suggest a lack of velocity-specific performance changes in elite concurrently training sprint runners performing a combination of traditional and semi-specific resistance training exercises.     

Measurement of total energy expenditure by the doubly labelled water method in professional soccer players

To determine the daily energy requirements of professional soccer players during a competitive season, we measured total energy expenditure in seven players (age 22.1 - 1.9 years, height 1.75 - 0.05 m, mass 69.8 - 4.7 kg; mean - s ) using the doubly labelled water method. Energy intake was simultaneously estimated from 7 day self-report dietary records. Mean total energy expenditure and energy intake were 14.8 - 1.7 MJ · day -1 (3532 - 408 kcal· day -1 ) and 13.0 - 2.4 MJ · day -1 (3113 - 581 kcal· day -1 ), respectively. Although there was a significant difference between total energy expenditure and energy intake ( P ? 0.01), there was a strong relationship between the two ( r = 0.893, P ? 0.01). Basal metabolic rate and recommended energy allowance calculated from the Recommended Dietary Allowances for the Japanese were 7.0 - 0.3 MJ ·day -1 (1683 - 81 kcal· day -1 ) and 15.6 - 0.8 MJ · day -1 (3739 - 180 kcal· day -1 ), respectively. A physical activity level (total energy expenditure/ basal metabolic rate) of 2.11 - 0.30 indicated that, during the competitive season, professional soccer players undertake much routine physical activity, similar to that of competitive athletes during moderate training. Energy intake estimated using dietary records was under-reported, suggesting that its calculation from these data does not predict energy expenditure in soccer players.     

影响我国青少年田径运动员成长因素的研究

为探索青少年田径运动员成长的影响因素,运用文献法、问卷法、数理统计分析等方法进行研究。结果表明,影响青少年运动员成长的因素分为内在动力因子、科学化训练因子、运动员心理能力因子、运动员专项能力因子、物质保障因子等5个因子。     

雅典奥运会世界田径10强及中国竞技能力分析

运用访谈法、文献资料法、观察法等研究方法,对世界各国及中国运动员参加2004年奥运会的竞技状况进行分析。结果表明：世界田径10强中,美国、俄罗斯是真正的田径强国;牙买加、埃塞俄比亚、肯尼亚、英国是田径较强国家;中国田径女强男弱的局面已改变,但整体竞技能力不高。我国要加大优势和潜优势项目的投入,增强训练的科技含量;加强教练员培养比赛型运动员的能力,不断缩小参赛能力和训练水平与田径强国的差距。