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1.
Abstract

The purpose of the present study was to relate 3D acceleration patterns of the lower and upper trunk during running to running gait cycle, assess the validity of stride duration estimated from acceleration patterns, investigate speed-dependent changes in acceleration, and examine the test–retest reliability of these parameters. Thirteen healthy young men performed two running trials each on a treadmill and on land at three speeds (slow, preferred, and fast). The 3D accelerations were measured at the L3 spinous process (lower trunk) and the ensiform process (upper trunk) and synchronised with digital video data. The amplitude and root mean square of acceleration and stride duration were calculated and then analysed by three-way analysis of variance to test effects of running conditions, device location, and running speed. Bland-Altman analysis was used to evaluate the test–retest reliability. Marked changes in acceleration were observed in relation to foot strike during running. Stride durations calculated from the vertical accelerations were nearly equal to those estimated from video data. There were significant speed effects on all parameters, and the low test–retest reliability was confirmed in the anterior–posterior acceleration during treadmill running and the anterior–posterior acceleration at slow speed during treadmill and overground running.  相似文献   

2.
Abstract

This study analysed how the relative positioning of players on court influenced patterns of interpersonal coordination in baseline rallies in tennis. We developed a model (PA index) that assigns a weight to the position of each player on court and determines a positional advantage, based on the relative proportionality between the lateral and longitudinal displacement values during rallies. To test the model, data from 27 randomly-selected baseline rallies from three ATP World Tour matches (professional tennis players' tournaments organized by Association of Tennis Professionals) on clay were analysed. Results revealed that the PA index of players on court described their interpersonal coordination dynamics during baseline rallies. It also identified the emergence of rally breaks in the interpersonal coordination patterns of competing dyads that led to a point being scored. Data suggest that positional advantage data may assist coaches in the design of training tasks to enhance players' court coverage and performance during competitive interactions, acting as a valuable tool for performance analysis in tennis.  相似文献   

3.

We tested the hypothesis that quiet eye, the final fixation before the initiation of a movement in aiming tasks, is used to scale the movement's parameters. Two groups of 12 participants (N = 24) threw darts to targets in the horizontal and vertical axes under conditions of higher (random) or lower (blocked) target variability. Supporting our predictions, random practice and target changes in the vertical axis led to longer quiet eye duration than did blocked practice and target changes in the horizontal axis. Our data suggest that quiet eye is not simply a mediating factor in accuracy, but is responsive to the task's programming demands, being influenced by the necessity to reparameterize the movement from one trial to the next.  相似文献   

4.
This study aimed at exploring whether 3D technology enhances tennis decision-making under the conceptual framework of human performance model. A 3 (skill-level: varsity, club, recreational)?×?3 (experimental condition: placebo, weak 3D [W3D], strong 3D [S3D]) between-participant design was used. Allocated to experimental conditions by a skill-level stratified randomization, 105 tennis players judged tennis serve direction from video scenarios and rated their perceptions of enjoyment, flow, and presence during task performance. Results showed that varsity players made more accurate decisions than less skilled ones. Additionally, applying 3D technology to typical video displays reduced tennis players’ decision-making accuracy, although wearing the 3D glasses led to a placebo effect that shortened the decision-making reaction time. The unexpected negative effect of 3D technology on decision-making was possibly due to participants being more familiar to W3D than to S3D, and relatedly, a suboptimal task-technology match. Future directions for advancing this area of research are offered.

Highlights

  • 3D technology augments binocular depth cues to tradition video displays, and thus results in the attainment of more authentic visual representation. This process enhances task fidelity in researching perceptual-cognitive skills in sports.

  • The paper clarified both conceptual and methodological difficulties in testing 3D technology in sports settings. Namely, the nomenclature of video footage (with/without 3D technology) and the possible placebo effect (arising from wearing glasses of 3D technology) merit researchers' attention.

  • Participants varying in level of domain-specific expertise were randomized into viewing conditions using a placebo-controlled design. Measurement consisted of both participants' subjective experience (i.e., presence, flow, and enjoyment) and objective performance (i.e., accuracy and reaction time) in a decision-making task.

  • Findings revealed that wearing glasses of 3D technology resulted in a placebo effect that shortened participants' reaction times in decision-making. Moreover, participants' decision-making accuracy decreased when viewing video scenarios using 3D technology. The findings generated meaningful implications regarding applying 3D technology to sports research.

  相似文献   

5.
Abstract

The effect of intellectual impairment on sports performance has received limited attention by researchers. As a contribution to closing this gap, the purpose of the present investigation was to examine the differences in tactical proficiency between table tennis players with and without intellectual disabilities (ID). These groups were matched for training-volume and experience and consisted of 41 male (age = 27±8) and 30 female (age= 28±8) elite players with ID and a reference group of 12 male (age= 24±12) and 5 female (age= 20±9) players without ID. In two different test settings – one a World Championship and the other a training camp – the players in each group performed 60 semi-standardised rallies against the same opponent. Players were told that 12 sets of five identical services would be delivered, and their goal was to return the service with the intention of ‘winning the point’. The test results were validated for this study, to compute tactical proficiency scores (maximal score of eight points) for each player. A two-way Analysis of Variance (ANOVA) revealed significantly lower proficiency scores for players with ID than for those without ID. Repeated-measures ANOVA revealed that within each series of five rallies, starting with identical services, all participants were able to significantly improve their tactical proficiency gradually, but players without ID scored 4.3±0.5 from the first ball on, and while athletes with ID only 3.3±0.7 after five balls. The results of this study indicate that ID is associated with decreased tactical proficiency in table tennis.  相似文献   

6.
ABSTRACT

Anterior cruciate ligament (ACL) injuries in badminton commonly occur during single-leg landing after an overhead stroke in the backhand-side court. This study compared differences in trunk acceleration and kinematic variables during single-leg landing in the forehand- and backhand-side courts after an overhead stroke. Eighteen female junior badminton players performed two singles games while wearing a tri-axial accelerometer. The moment that over 4g of resultant acceleration was generated was determined using synchronised video cameras. Trunk lateral inclination and hip abduction angles at the point of landing with over 4g of resultant acceleration were analysed. Mediolateral acceleration in the backhand-side court was greater than that in the opposite-side court (p < 0.001, ES = 0.840). Both trunk lateral angles were larger than those previously reported in injured participants and the hip abduction angle in the backhand-side court was larger than that in the forehand-side court (p < 0.001, ES = 2.357). The lateral and vertical acceleration in the backhand-side court showed moderate-to-strong correlations with the trunk and hip angles. The mediolateral physical demand and high-risk posture in the backhand-side court may be associated with a higher incidence of knee injuries during badminton games.  相似文献   

7.
Abstract

The purpose of this study was to examine the accuracy of the ePulse Personal Fitness Assistant, a forearm-worn device that provides measures of heart rate and estimates energy expenditure. Forty-six participants engaged in 4-minute periods of standing, 2.0 mph walking, 3.5 mph walking, 4.5 mph jogging, and 6.0 mph running. Heart rate and energy expenditure were simultaneously recorded at 60-second intervals using the ePulse, an electrocardiogram (EKG), and indirect calorimetry. The heart rates obtained from the ePulse were highly correlated (intraclass correlation coefficients [ICCs] ≥0.85) with those from the EKG during all conditions. The typical errors progressively increased with increasing exercise intensity but were <5 bpm only during rest and 2.0 mph. Energy expenditure from the ePulse was poorly correlated with indirect calorimetry (ICCs: 0.01–0.36) and the typical errors for energy expenditure ranged from 0.69–2.97 kcal · min?1, progressively increasing with exercise intensity. These data suggest that the ePulse Personal Fitness Assistant is a valid device for monitoring heart rate at rest and low-intensity exercise, but becomes less accurate as exercise intensity increases. However, it does not appear to be a valid device to estimate energy expenditure during exercise.  相似文献   

8.
ABSTRACT

This study used the intensity gradient (IG) and average acceleration metrics to describe children’s activity profiles and explore associations with body mass index (BMI) z-score. Two hundred and forty-six children (n = 138 girls) aged 9.6 ± 1.4 years wore a wrist-mounted ActiGraph wGT3X-BT accelerometer for 7 days on their non-dominant wrist. Physical activity (PA) metrics captured included: the IG which describes the intensity distribution of accelerations across the 24 h monitoring period; average acceleration which provides a measure of the volume of activity; total moderate-to-vigorous PA (MVPA) and inactive time. Acceleration was averaged over 5s epochs. Finally, BMI z-score was calculated for each participant. Average acceleration was negatively associated with BMI z-score (p < 0.05) independent of age and gender but not IG. The IG was negatively associated with BMI z-score independent of potential correlates and average acceleration. Total MVPA was not associated with BMI-z score. The IG and average acceleration metrics may be used to explore the independent or cumulative effects of the volume and intensity distribution of activity upon measures of health and well-being in children to inform specific activity recommendations.  相似文献   

9.
Abstract

This study examined the effects of knowledge of results (KR) delay and subjective estimation of movement form on the acquisition and retention of a motor skill. During acquisition, four groups of participants performed 60 trials of a throwing accuracy task under the following conditions: (a) immediate KR, (b) delayed KR, (c) immediate KR + form estimation, and (d) delayed KR + form estimation. Retention tests of throwing accuracy and outcome error estimation in the absence of visual KR were administered 5 min and 24 hours following acquisition. Throwing accuracy was significantly higher during acquisition but significantly lower during retention for immediate-KR participants than for delayed-KR participants. However, participants who estimated their movement form during acquisition produced significantly higher throwing accuracy and lower estimation error during retention than those who did not.  相似文献   

10.
Purpose

This study investigated whether within-task expertise affects the reported asymmetry in execution time exhibited in reactive and self-initiated movements.

Method

Karate practitioners and no-karate practitioners were compared performing a reverse punch in reaction to an external stimulus or following the intention to produce a response (self-initiated). The task was completed following the presentation of a specific (i.e., life-size image of opponent) or general stimulus and in the presence of click trains or white noise.

Results

Kinematic analyses indicated reactive movement had shorter time to peak velocity and movement time, as well as greater accuracy than self-initiated movement. These differences were independent of participant skill level although peak velocity was higher in the karate practice group than in the no-karate practice group. Reaction time (RT) of skilled participants was facilitated by a specific stimulus. There was no effect on RT or kinematic variables of the different type of auditory cues.

Conclusions

The results of this study indicate that asymmetry in execution time of reactive and self-initiated movement holds irrespective of within-task expertise and stimulus specificity. This could have implications for training of sports and/or relearning of tasks that require rapid and accurate movements to intercept/contact a target.  相似文献   

11.
Abstract

The purpose of this study was to validate peak acceleration data from an accelerometer contained within a wearable tracking device while walking, jogging and running. Thirty-nine participants walked, jogged and ran on a treadmill while 10 peak accelerations per movement were obtained (n = 390). A single triaxial accelerometer measured resultant acceleration during all movements. To provide a criterion measure of acceleration, a 12-camera motion analysis (MA) system tracked the position of a retro-reflective marker affixed to the wearable tracking device. Peak raw acceleration recorded by the accelerometer significantly overestimated peak MA acceleration (P < 0.01). Filtering accelerometer data improved the relationship with the MA system (P < 0.01). However, only the 10 Hz and 8 Hz cut-off frequencies significantly reduced the errors found. The walk movement demonstrated the highest accuracy, agreement and precision and the lowest relative errors. Linear increases in error were observed for jog compared with walk and for run compared to both other movements. As the magnitude of acceleration increased, the strength of the relationship between the accelerometer and the criterion measure decreased. These results indicate that filtered accelerometer data provide an acceptable means of assessing peak accelerations, in particular for walking and jogging.  相似文献   

12.

We used data from the American Time Use Survey (years 2003–06) to analyze whether the intensity and duration of high school students' (ages 15–18 years) sports and exercise bouts differed across physical and social environments. Boys' sports and exercise bouts were more likely to reach a vigorous intensity when taking place at school and with friends/acquaintances/other people; whereas girls' sports and exercise bouts were more likely to reach a vigorous intensity when outdoors and alone. For boys and girls, bout durations were greater at school and with friends/acquaintances/other people than in other environments. Overall, environmental influences on the intensity but not duration of sports and exercise bouts appear to differ between boys and girls.  相似文献   

13.
Abstract

The aim of the study was to examine the relationships between physical activity and several health parameters in German adolescents. We predicted that the association between physical activity and physical and psychosocial health resources (physical and psychosocial characteristics that tend to enhance coping and well-being) would be stronger than the association between physical activity and health deficits. This research is based on a large representative, cross-sectional study (the German Health Interview and Examination Survey [KiGGS] and the Motoric-Module [MoMo]). Health was assessed using medical parameters, motor fitness data, and questionnaire data for various health-related parameters. To assess physical activity, the participants answered questions regarding the duration and intensity of weekly physical activity in leisure and organized sports. We tested our assumptions using a representative sample (N=2291; 50.5% boys) of German adolescents aged 11–17 years. Participants were classified as physically inactive (16.7%), somewhat active (24.7%), medium active (19.8%), active (14.4%) or highly active (24.4%), based on the duration and intensity of their weekly physical activity. In support of our hypothesis, the data revealed that the amount of physical activity explains up to 12.6% in the variance of physical and psychosocial health resources, but only 2.5% of the variance in physical and psychosocial health deficits. We conclude that the relationship between physical activity and health among adolescents should not only be viewed as a way of reducing health deficits, but should also focus on the enhancement of physical and psychosocial resources.  相似文献   

14.
Abstract

The aim of this study was to summarize both practical and methodological issues in using pedometers to assess physical activity in a large epidemiologic study. As part of a population-based survey of cardiovascular disease risk factors, physical activity was assessed using pedometers and activity diaries in 775 men and women ages 25–64 years who were residents of Burnie, Tasmania, 1998–99. Common data problems were classified by type. The frequency of each problem and the methods used to identify it are reported along with strategies to correct or prevent each problem type. Pedometer data from 15 (1.9%) participants could not be used due to errors in completing the pedometer protocol. Among 760 participants with usable data, the median number of steps was 9,729 for men and 10,388 for women. Pedometer steps per day were modestly correlated (r = .20, p < .0001) with the duration of pedometer wear, which ranged from 4.50 to 21.75 hr. Adjustment for wear time, however, did not alter observed correlations between pedometer steps and cardiovascular risk factors. The authors conclude that pedometers can be used in large population studies with a relatively low frequency of data errors. However, guidelines for consistent data collection and interpretation are needed.  相似文献   

15.
ABSTRACT

Background: Over the past 10 years, research has started to investigate the pedagogic practices of instructors and coaches working in adventure sports settings. Outdoor instructors face particular challenges regarding the impact the dynamic environment has on the coaching process and their students. This challenging combination of factors obliges the instructor to be agile in response. We propose that this adaptive expertise is characteristic of these factors and that adaptability may be a beneficial focus of outdoor instructor training and education.

Purpose: The major aim was to identify if adaptive expertise is an attribute of outdoor instructors? And if so, what are its characteristics in this context?

Research design and data collection: We applied a mixed methodology to a sample of outdoor instructors (n?=?64). The instructors were asked to complete a quantitative adaptive expertise inventory. We then interviewed a selected sub-sample (n?=?12).

Participants and setting: Quantitative data was collected from outdoor instructors working in the UK (n?=?64). The sample consisted of instructors qualified to work independently with groups in adventurous settings in a range of activities. Qualitative data was collected from a smaller sample (n?=?12) via a series of thematically analysed semi-structured interviews.

Findings: Results suggest that the participating outdoor instructors have high levels of adaptive expertise. A characteristic of that adaptive capacity is a combination of skills revolving around reflection, metacognition, and situational awareness. There were differences, however, between less and more experienced outdoor instructors in their adaptive capacity, with less experienced instructors being adaptive to a lesser extent.

Conclusions: The implication is that further research is worthwhile to examine the development of instructors’ adaptive capacity. The training and education of outdoor instructors requires pedagogic approaches that facilitate and engender adaptability, flexibility and agility in neophyte instructors.  相似文献   

16.
Abstract

A classification system of treading water based on a conceptual typology was first established and then verified empirically. The typology was established on two concepts: the nature of the forces created within the water and the type of inter-limb coordination used. Thirty-eight participants were videotaped while treading water. Multivariate statistics were used to understand how the different behavioural types related to expertise. Three distinct groups of coordination patterns were adopted during treading water. A support vector machine procedure was used as a confirmatory procedure. The data mining process provides a methodological framework to analyse expertise in sports activities, and in this context suggests that a taxonomy can be established among the numerous coordination solutions that allow humans to create stabilising forces in the water.  相似文献   

17.
ABSTRACT

This study developed and evaluated machine learning algorithms to predict children’s physical activity category from raw accelerometer data collected at the hip. Fifty participants (mean age = 13.9 ± 3.0 y) completed 12 activity trials that were categorized into 5 categories: sedentary (SED), light household activities and games (LHHAG), moderate-vigorous games and sports (MVGS), walking (WALK), and running (RUN). Random Forest (RF) and Logistic Regression (LR) classifiers were trained with features extracted from the vector magnitude using 10?s non-overlapping windows. Classification accuracy was evaluated using leave-one-subject-out cross validation. Overall accuracy for the RF and LR classifiers was 95.7% and 94.3%, respectively. Classification accuracy was excellent for SED (96.3% – 98.1%), LHHAG (92.3% – 95.2%), WALK (94.5% – 97.1%), RUN (99.5% – 99.6%); and MVGS (87.5% – 92.7%). The results indicate that classifiers trained on features in the raw acceleration from the hip can be used for activity recognition in young people.

Abbreviations: VM: Vector Magnitude; RF: Random Forest; LR: Logistic Regression; LOSO: Leave-One-Subject-Out  相似文献   

18.
Abstract

Using a scrambled sentence priming protocol, the first aim of this study was to investigate whether differences in novel exercise-related goals existed between participants primed with motivational or non-motivational material (i.e. autonomous, controlled or neutral primes). The second aim was to explore whether an indirect effect was present between priming condition and the goal-related exercise sessions that individuals performed over the week following administration of the prime. No effects were observed across priming conditions with respect to subjective vitality, goal concordance and the frequency with which participants planned to exercise. However, autonomy-primed individuals set goals for their exercise sessions that were significantly longer in intended duration (M = 57.72 min, SD = 37.42) than those set by their counterparts in both the controlled-prime condition (M = 44.12 min, SD = 27.78) and the neutral-prime condition (M = 37.10 min, SD = 20.47). Bootstrapped analyses also revealed a significant indirect relationship between prime and exercise behaviour, with the autonomy prime predicting longer goal-based exercise sessions, via the effect on the duration of participants’ intended exercise sessions. These findings highlight the potential influence that priming autonomous motivation may have on individuals’ exercise aspirations, as well as the way in which primes may indirectly shape exercise engagement.  相似文献   

19.
Abstract

In tournaments in various sports that feature one–on–one competition, the trophy is sometimes prominently displayed near the athletes during the final. Based on recent research on subtle reward cues, we propose that such trophies have the potential to induce choking under pressure in the match favourites, who are known to be most at risk. To test this idea, we analysed real-life tennis performance data (service performance and rally performance) from professional tournaments. While favourites generally outperformed underdogs during rallies, they did not do so in finals in which (a) large amounts of money were at stake and (b) a trophy was on display near the court. These findings support the idea that tournament trophies may distract favourites by continuously reminding them of what is at stake, and via that route may severely thwart their performance.  相似文献   

20.
ABSTRACT

This study examined the age-specific development of vertical jump height, straight and change-of-direction (COD) speed, and COD deficit in one-hundred and eighty-two elite soccer players from different age-categories (U15, U17, U20, and Senior). All participants were players of two distinct clubs and were undertaking different training routines, as planned by their technical staff members. For this purpose, the soccer players performed: (1) squat and countermovement jumps; (2) a maximal 20-m linear sprint speed test, and (3) the Zigzag COD test. The magnitude-based inference approach and standardized differences were used to compare the age-groups. Sprint speed at longer distances (20-m) increased progressively across the age-ranges. In contrast, speed and acceleration performances at shorter distances (5-m) were better in U15 than in the other age-categories. The COD speed did not change throughout the younger categories but presented a meaningful decrease in the Senior category. Surprisingly, despite the progressive increase in volume and intensity of neuromuscular training from younger to older categories, the COD deficit presented a gradual increase across the age-groups. It is possible that simple modulation of the strength-power training program during the maturation process is not sufficient to produce faster adult players with enhanced ability to change direction. Therefore, coaches are strongly encouraged to implement specific COD training practices to tolerate braking at increasing running speeds and appropriate volume and intensity of soccer specific training throughout the players’ specialization process.  相似文献   

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