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1.
Abstract

Equations by Jackson, Pollock, and Ward (1980) and by Durnin and Womersly (1974) for estimating body density (BD) from skinfolds (SF) purportedly overcome the criticism of “population specificity” by taking into account age and the curvilinear relationship between SFs and BD. Selected equations were validated on 79 women athletes against %fat and fat(kg) measured by underwater weighing. Equations by Sloan, Burt, and Blyth (1962), Wilmore and Behnke (1970), and Katch and McArdle (1973) were also evaluated to compare the newer equations to older ones. The mean estimate of %fat by one equation by Jackson et al. utilizing the sum of triceps, abdomen, suprailiac and thigh SF was the same as the true value (20.1%) and correlated .795 (SEE ± 3.27 total error 3.23). Regression analysis showed it to have acceptable accuracy over the range of sample values (10.3–34.0%). The Durnin-Womersly equations overestimated %fat by 3.9 to 4.4% and were not acceptable. For the older equations, the mean Sloan et al. estimate (20.8 %Fat) was not significantly different from the true value and correlated .779 (SEE ± 3.37 total error 3.47). Regression analysis showed it to overestimate fat in leaner subjects and to underestimate it in fatter ones, making it unacceptable. The Wilmore-Behnke equation overestimated %fat by 4.3%. Equations by Jackson et al., using the sum of triceps, suprailiac and thigh skinfolds, and by Katch and McArdle were shown to be acceptable if the ordinate values were adjusted (1.0994921 to 1.1074921 and 1.08347 to 1.09147 respectively) to account for the higher density of women athletes.  相似文献   

2.
Abstract

The purpose of this study was to establish the characteristics of the movement patterns common to flutter kicking of skilled swimmers and to determine how the movement patterns of swimmers at different levels of a “learn-to-swim” programme differ from those of skilled swimmers. Also, the nature of the skill afforded the opportunity to investigate learning of a cyclical multi-joint task from a motor control perspective. The underwater motion of nine children representing three levels of a “learn-to-swim” programme and 10 skilled swimmers were video-recorded while performing nine cycles of prone flutter kicking. Kinematics including joint angular motion and coordination of joint actions were calculated. Fourier analysis was applied to determine the frequency composition of the vertical undulations of the hip, knee, and ankle and to calculate the velocity of the body wave travelling caudally from hip to ankle. Fourier analysis also enabled investigation of biological noise, as distinct from variability. The results indicated the desired joint angles and coordination towards which learners could be guided. An index based on the ratio of hip – knee and knee – ankle body wave velocities showed that the inter-joint coordination of most learners was not appropriate for effective flutter kicking. There was strong evidence to suggest that skilled performance in flutter kicking is characterized by sequencing of joint actions to produce a single sinusoidal body wave moving caudally with not decreasing and preferably increasing velocity, low biological noise, and small variability.  相似文献   

3.
Abstract

The purpose of this investigation was to quantify the body composition of speed skaters who were candidates for the 1980 United States Olympic Team. Subjects were 19 males between 16 and 27 years of age. Most subjects had just completed three months of intensive dry-land training. Seven skinfold fat, 11 circumference, and seven diameter sites were measured. Body density was determined by underwater weighing. Study of the speed skaters (mean ± standard deviation) gave the following results: height, 176 ± 8 cm; body weight, 69.6 ± 7.0 kg; body density, 1.081 ± 0.006 g/ml; and relative fat, 7.6 ± 2.6%. The eight speed skaters who were selected for the Olympic Team were significantly older, taller, and heavier in total body weight and fat free weight (FFW) than the non-Olympians. Thus, years of training and greater FFW may help differentiate international caliber male speed skaters. Data on Olympic speed skating candidates from 1968 showed them to be of similar age (20.1 yr) and height (176 cm), but greater in body weight (73.9 kg). Relative fat was not determined but the body mass index (Wt/ht2) showed that the present speed skaters may be leaner (24.0 vs 22.2). These differences in body composition were thought to be, in part, a result of the more rigorous training program currently used by speed skaters. The body composition of the speed skaters was also compared to that of other athletic groups.  相似文献   

4.
Abstract

The purpose of this investigation was to determine the yearly changes in body composition as well as absolute and relative isokinetic forearm flexion and extension strength of high school wrestlers. Evaluations of body composition (underwater weighing) were performed on 27 high school wrestlers prior to three consecutive seasons. In addition, isokinetic forearm flexion and extension strength values at 180°/s (Cybex II) were available for 20 of the subjects. The mean ages at the times of laboratory testing were 15.5 (± .5), 16.5 (± .5), and 17.5 (± .5) years. Repeated measures ANOVA or ANCOVA with Tukey post-hoc comparisons were used to locate significant (p<.05) differences across age for height, body weight, relative fat, body density, fat weight, fat-free weight, absolute muscular strength, and muscular strength covaried for body weight and fat-free weight. There were yearly increases in all variables except fat weight, forearm flexion covaried for fat-free weight and forearm extension covaried for fat-free weight. The results of this study indicated that the improved wrestling performance and the increase in weight classification which normally occurs during high school are, in part, a function of yearly changes in body composition and muscular strength.  相似文献   

5.
Abstract

The data for 40 variables were obtained from 81 Purdue University faculty sons between 10 and 12 years of age inclusive. Among the 40 variables, 680 correlation coefficients were obtained. Factor analysis was used to identify the factors which could explain the items measuring body composition and motor aptitude. As a result, eight factors were isolated and given names. The factors underlying the 40 variables seemed to permit the following names: growth and maturity factor, “body fitness” factor, body balance on object factor, coordination of the lower extremities factor, general kinesthetic sense factor, general static balance factor, directionality factor, and laterality factor. Observing the factor loadings in Factor I, it may be concluded that the measurement of lean body weight by liquid scintillation counting technique is significant in the assessment of growth and maturity in preadolescent boys. Furthermore, in the assessment of “body fitness” pertaining to preadolescent boys, it is revealed that the percent lean body weight is the most important item as indicated by the value of factor loading presented in Factor II.  相似文献   

6.
Abstract

The purpose of this study was to determine the effects of aerobic dance on physical work capacity, cardiovascular function and body composition of young middle-aged women. Maximal oxygen uptake ([Vdot]O 2 max), heart rate during submaximal treadmill walking, resting heart rate and blood pressure, and body composition were determined before and after a 10-week aerobic dance conditioning program in 28 women (18 experimental and 10 control), aged 25 to 44 years. During the 10-week treatment period, the experimental subjects participated in 45 min of aerobic dance at 70–85% of the heart rate reserve, 3 days · week –1,whereas the control group did not participate in any regular strenuous physical activity. Changes in the experimental group were significantly greater than in the control group for [Vdot]O 2 max expressed in 1 · min –1 or relative to body weight or fat-free weight (5 to 7% vs. – 5 to – 8%), time on a continuous grade-incremented walking treadmill test (16% vs. 1%), heart rate during submaximal stages of the treadmill test (– 9% vs. 1%) and resting heart rate (– 8% vs. 2%). Resting systolic and diastolic blood pressure; body weight; percent fat, fat weight, and fat-free weight estimated using underwater weighing; sum of seven skinfolds; and sum of seven circumferences did not change significantly in either group. It was concluded that aerobic dance performed 30–45 min, 3 days · week –1 for 10 weeks significantly improves physical work capacity and cardiovascular function, but without dietary control, does not alter body composition in sedentary middle-aged women.  相似文献   

7.
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8.
Abstract

The efficiency of two practice schedules was examined on two large muscle motor tasks. There were four groups of subjects (N = 160); each individual in a group performed on one of the two motor tasks under one of the two conditions. Distributed practice consisted of alternating 30-second trials of practice and rest; massed practice was continuous for 8 minutes. Comparisons made during the last minute of practice prior to the rest pause revealed that the massed groups had significant decrements in performance level. In contrast, after the rest period, when both groups were on a distributed schedule, no difference was found in the amount of learning. Learning was found to be a function of the number of trials and independent of the conditions of practice.  相似文献   

9.
Abstract

The most recent (1996) drinking guidelines of the American College of Sports Medicine (ACSM) propose that athletes should drink “as much as tolerable” during exercise. Since some individuals can tolerate rates of free water ingestion that exceed their rates of free water loss during exercise, this advice has caused some to overdrink leading to water retention, weight gain and, in a few, death from exercise-associated hyponatraemic encephalopathy. The new drinking guidelines of the International Olympic Committee (IOC), recently re-published in this Journal, continue to argue that athletes must drink enough to replace all their weight lost during exercise and to ingest sodium chloride since sodium is “the electrolyte most critical to performance and health”. In this rebuttal to that Consensus Document, I argue that these new guidelines, like their predecessors, lack an adequate, scientifically proven evidence base. Nor have they been properly evaluated in appropriately controlled, randomized, prospective clinical trials. In particular, these new guidelines provide erroneous recommendations on five topics.

If novel universal guidelines for fluid ingestion during exercise are to be promulgated by important international bodies including the IOC, they should first be properly evaluated in appropriately controlled, randomized, prospective clinical trials conducted under environmental and other conditions that match those found in “out-of-doors” exercise. This, and the potential influence of commercial interests on scientific independence and objectivity, are the two most important lessons to be learned from the premature adoption of those 1996 ACSM drinking guidelines that are not evidence-based. These concerns need to be addressed before the novel IOC guidelines are accepted uncritically. Otherwise the predictable consequences of the premature adoption of the 1996 ACSM guidelines will be repeated.  相似文献   

10.
Background:Football is the most practised sport in the world and is associated with the risk of injuries in the players.Some studies have been published that identify injury prevention programs,but there is no review of the full body of evidence on injury prevention programs for use by football coaches.The aim of this article was to carry out a systematic review of published studies on injury prevention programs for adult male footballers,identify points of common understanding and establish recommendations that should be considered in the design of injury prevention strategies.Methods:PubMed and EMBASE databases were used to identify relevant published articles using the following keywords:"soccer"AND"injury"AND"prevention".Results:A total of 2512 studies were identified initially,but only 11 studies met the inclusion criteria,and their outcomes are presented.Results revealed that injury prevention programs in football have focused on strength training,proprioceptive training,multicomponent programs(balance,core stability,and functional strength and mobility),and warm-up programs.Conclusion:Based on results from the studies analyzed,football players can lower the incidence of match and training injuries by participating in dynamic warm-up programs that include preventive exercises before games or during training sessions,and by adding strength,balance,and mobility training to the training sessions.  相似文献   

11.
Abstract

Three hundred male subjects, assigned in systematic rotation to five experimental groups (N = 60 in each) which differed in amount of distribution of practice, were tested on a discrete-trial motor learning task, the peg turn. All subjects were given 120 practice trials (60 trials a day), on two days separated by a 48-hour rest. Even though the peg turn task is inherently distributed, reminiscence did occur when the massing was made as large as practically possible. The amount of reminiscence depended upon the stage of practice. Warm-up decrement occurred in the peg turn under both massed and distributed practice conditions; the longer the rest, the greater the amount. Performance of the task under nonrhythmical conditions reduced the development of “set” during practice and thus decreased the amount of warm-up decrement after rest. Increased amounts of massing did have a deleterious effect on performance, but did not reduce the amount learned.  相似文献   

12.
Abstract

The problems of this study were to investigate the interrelationship of selected functional and body form measures, and to examine the differences between groups varying in activity levels. The volunteers for the study, 35 college women, were placed in activity groups termed “most active” and “least active” according to their response on an activity history-recall questionnaire. Functional measures included strength and flexibility. Strength was measured with a cable tensiometer and followed the procedures outlined by H. H. Clarke. Flexibility was measured using a Leighton Flexometer. Body form measures included height, weight, percent body fat, fat free body weight, specific gravity, and ponderal index. The range, mean, and standard deviation were computed for all parameters. The Pearson product-moment correlation was employed to determine interrelationships of all variables. Equality of variances among selected parameters was determined by the F test; Cochran-Cox and two sample t tests were used to determine the equality of means among selected parameters in the activity groups. Significant differences at the .05 level were found between the means of weight, fat free body weight, trunk extension flexibility, with the most active group exhibiting higher values. The least active group showed significantly greater shoulder extension flexibility, shoulder inward rotation flexibility, and ankle flexion flexibility.  相似文献   

13.
Abstract

Non-motorised underwater treadmills are commonly used in fitness activities. However, no studies have examined physiological and biomechanical responses of walking on non-motorised treadmills at different intensities and depths. Fifteen middle-aged healthy women underwent two underwater walking tests at two different depths, immersed either up to the xiphoid process (deep water) or the iliac crest (shallow water), at 100, 110, 120, 130 step-per-minute (spm). Oxygen consumption (VO2), heart rate (HR), blood lactate concentration, perceived exertion and step length were determined. Compared to deep water, walking in shallow water exhibited, at all intensities, significantly higher VO2 (+13.5%, on average) and HR (+8.1%, on average) responses. Water depth did not influence lactate concentration, whereas perceived exertion was higher in shallow compared to deep water, solely at 120 (+40%) and 130 (+39.4%) spm. Average step length was reduced as the intensity increased (from 100 to 130 spm), irrespective of water depth. Expressed as a percentage of maximum, average VO2 and HR were: 64–76% of peak VO2 and 71–90% of maximum HR, respectively at both water depths. Accordingly, this form of exercise can be included in the “vigorous” range of exercise intensity, at any of the step frequencies used in this study.  相似文献   

14.
Abstract

Although research into coaching has increased considerably during the last two decades, an area of neglect has been that of the professional youth coach. The aim of this study was to investigate the working behaviours of six top-level professional soccer coaches. Data were collected using a modified version of the Arizona State University Observation Instrument and semi-structured interviews. The triangulation of the data ensured that both the “what” and the “why” of the coaches' behaviour were considered. Results revealed a conscious and well thought out pattern of behaviour: silently monitoring, interspersed with clips of instruction coupled with praise and encouragement. The interviews revealed three themes underpinning this behaviour: developing game understanding, support and encouragement, and coaches' role and influences. The use of silence was the largest single behaviour, the efficacy of which was considered in light of theories of experiential and discovery learning.  相似文献   

15.
Abstract

Despite significant advances in the diagnostics and treatment of knee injuries over the last decade, several challenges related to the subject “return to sport” remain largely unknown. For example, how should “return to sport” be defined precisely? What is the optimal timing and progression to enable a return to sport? Which criteria should be used during this process? What type of training is indicated? Which measurements can support the decision-making process? How do we optimally prepare athletes for competition without risking re-injury?

This paper critically addresses these questions, and proposes a return to play model to prepare football players to compete after major knee surgery (anterior cruciate ligament reconstruction, cartilage repair). The goal is to re-integrate the player gradually into the game, taking into account his individual characteristics. Several evidence-based and empirical criteria are needed to plan and monitor the efficient return to competitive football. Injury-prevention education should be part of this process to maximise the chance of a durable career and decrease the risk of re-injury.

However, because of the paucity of research on “return to sport”, further research is more than warranted.  相似文献   

16.
Abstract

The purpose of this study was to test the effects of a 10-month exercise program on bone mineral content (BMC) and bone mineral content/bone width (BMC/BW) of postmenopausal women. Thirty-one women (ages 57-83) completed either a general aerobics exercise program (n = 10), a general aerobics plus upper body weight training exercise program (n = 10), or served as nonexercising control subjects (n = 11). Average compliance rates for the exercise subjects ranged from 72 to 80%. All subjects were pre- and posttested for BMC and BMC/BW in the radius of the nondominant forearm. ANOVA results indicated that there were significant differences between the exercise and control subjects in the amount of change in BMC and in BMC/BW (p < .05) during the course of the study. The exercise subjects experienced mean increases of 1.38% and 1.33% in BMC and BMC/BW, respectively, whereas the control group had decreases of 2.50% and 258%. No significant differences were found for subjects in the two types of exercise programs, suggesting that the effects of exercise relative to maintenance of bone density may be general as well as localized.  相似文献   

17.
Jockeys regularly engage in rapid weight-loss practices in preparation for competition. These practices are thought to impair cognitive function, although the evidence in support of this theory remains inconclusive. The purpose of this study was to examine the effects of making-weight on cognitive function in apprentice jockeys in a simulated and competitive environment. Apprentice jockeys (n = 12) reduced their body mass by 4% in 48 h in a simulated environment using weight-loss methods typically adopted in preparation for racing. Simple and choice reaction time, attention, learning and memory were assessed before and after the weight loss. A further 10 apprentice jockeys performed the cognitive function assessment in a competitive racing environment at both a self-reported “normal” and “light” body mass. Hydration status and body mass were assessed in all trials. In the simulated environment, body mass was reduced by 4.2 ± 0.3%, yet no change in cognitive function was observed. Cognitive function also remained unchanged in the competitive environment after a body mass loss of 5.7 ± 1.9%. Typical reductions in body mass in preparation for racing have no effect on cognitive function in apprentice jockeys in a simulated and competitive environment. Further research is required to investigate the physiological mechanisms preventing the adverse effects of making-weight on cognitive function in jockeys.  相似文献   

18.
Abstract

Previous studies that have examined self-efficacy–performance relationships have used novice performers. It is unclear if these findings would generalize to “experienced” performers. Based on Bandura's self-efficacy theory, this study was designed to investigate (a) the effects of false information feedback on self-efficacy beliefs and subsequent weightlifting performance, and (b) whether self-efficacy or past performance is most related to subsequent weightlifting performance. Experienced weightlifters engaged in six performance sessions, each consisting of a one-repetition-maximum bench press. Male subjects (N = 36) were randomly assigned to one of three treatment groups: accurate performance information, false information that they lifted more than their actual lift, or false information that they lifted less than their actual lift. Before each session, subjects indicated the amount of weight they were 100%, 75%, and 50% confident they could lift. Results replicated existing research findings regarding deception and performance; false positive feedback increased future bench press performance. In addition, results indicated that past weightlifting performance accounted for nearly all of the variance in subsequent performance. This finding is discussed in light of the difficulty in extending the predictions of self-efficacy theory to sport settings where athletes have gained experience by undergoing repeated training trials.  相似文献   

19.
Abstract

The aim of this study was to examine the relationship between shoulder alignment and elbow angle during the delivery action of fast-medium bowlers. The elbow and upper trunk alignment were recorded for 13 high-performance bowlers (mean age 20 years) using a 12-camera Vicon motion analysis system operating at 250 Hz. The three highest velocity trials for “good” and “short” length deliveries were analysed. Results showed that bowlers with a more front-on shoulder alignment at back-foot impact and when the upper arm was horizontal to the ground experienced a significantly greater elbow flexion – extension range when compared with those who had a more side-on orientation at the same point in the delivery action. Bowlers with greater shoulder counter-rotation also recorded higher elbow flexion and subsequently extension during the period from upper arm horizontal to ball release. Shoulder alignment and elbow angles were similar for “short” and “good” length deliveries. It was concluded that bowlers with a more front-on shoulder orientation at back-foot impact demonstrated a higher elbow extension from upper arm horizontal to ball release and are therefore more likely to infringe International Cricket Council elbow tolerance levels, compared with those who adopt a more side-on shoulder orientation at back-foot impact.  相似文献   

20.
Editorial     
The aims of this study were to assess the validity and reliability of body volume and percent body fat determined by sulphur hexafluoride dilution, using underwater weighing as the criterion method, and to determine the influence of the magnitude of body volume. Thirty-one healthy Japanese individuals aged 18-27 years (16 males: height 1.70 - 0.06 m, mass 64.8 - 7.7 kg; 15 females: height 1.60 - 0.05 m, mass 55.2 - 6.2 kg; mean - s) participated in the study. Sulphur hexafluoride dilution measures the concentration of sulphur hexafluoride gas in the chamber (BSF-200, Shimazu Corp.). Underwater weighing was performed five times using a weight scale (AD-6204, A&;D) after residual volume had been determined (System9, Minato Medical Corp.). There were no significant differences in the mean between two trials for body volume, body density or percent body fat determined by sulphur hexafluoride dilution. The intra-class correlation coefficient of these variables ranged from 0.985 to 0.999. The results suggest that sulphur hexafluoride dilution is a reliable method for assessing body composition. There was no significant difference in body volume or percent body fat between sulphur hexafluoride dilution (males: 61.3 - 7.6 litres, 18.4 - 6.7%; females: 52.8 - 6.9 litres, 21.0 - 8.9%) and underwater weighing (males: 60.6 - 7.0 litres, 15.6 - 3.5%; females: 53.0 - 6.5 litres, 23.7 - 6.1%) and there was a high correlation between the two ( r = 0.997, P ? 0.05). A Bland-Altman plot of the difference between percent body fat estimated by underwater weighing and sulphur hexafluoride dilution versus average percent body fat by the two methods showed no systematic difference (mean difference =- 0.12 - 6.6 kg). The upper and lower limits of agreement were 13.2% and-13.4%, respectively. Determination by sulphur hexafluoride dilution resulted in both over- and underestimations in body volume and the difference between the two body volumes (determined by underwater weighing and by sulphur hexafluoride dilution) was inversely proportional to the mean body volume by the two methods. This suggests that improvements need to be made to the device or to the technique to maintain a constant volume of sulphur hexafluoride in the chamber.  相似文献   

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