共查询到20条相似文献，搜索用时 735 毫秒
1.
The impact absorption characteristics of cricket batting helmets 总被引：1，自引：0，他引：1
Stretch RA 《Journal of sports sciences》2000,18(12):959-964
To determine whether the helmets currently used by cricket batsmen offer sufficient protection against impacts of a cricket ball, the impact absorption characteristics of six helmets were measured using the drop test at an impact velocity equivalent to a cricket ball with a release speed of 160 km x h(-1) (44.4 m x s(-1)). An accelerometer transducer attached to a 5.0 kg striker was dropped from a height of 3.14 m onto the batting helmets to measure the impact characteristics at the three different impact sites: right temple, forehead and back of the helmet. These data were further expressed as a percentage above (-) or below (+) the recommended safety standard of 300 g. The results indicate that the force absorption characteristics of the helmets showed inter- and intra-helmet variations, with 14 of the 18 impact sites (66.7%) assessed meeting the recommended safety standards. Helmets 1, 2 and 4 succeeded in meeting the safety standards at all impact sites; helmets 5 and 6 both failed at the back and forehead, while helmet 3 failed at all impact sites. These differences were due to the structure and composition of the inner protective layer of the helmets. The helmets that succeeded in meeting the standards were made with a moulded polystyrene insert, a heat-formed ethylene vinyl acetate (EVA) insert, or EVA with a relatively high density that allows a minimal amount of movement of the helmet at ball impact. 相似文献
2.
Richard A. Stretch 《Journal of sports sciences》2013,31(12):959-964
To determine whether the helmets currently used by cricket batsmen offer sufficient protection against impacts of a cricket ball, the impact absorption characteristics of six helmets were measured using the drop test at an impact velocity equivalent to a cricket ball with a release speed of 160 km·h-1 (44.4 m·s -1 ). An accelerometer transducer attached to a 5.0 kg striker was dropped from a height of 3.14 m onto the batting helmets to measure the impact characteristics at the three different impact sites:right temple, forehead and back of the helmet. These data were further expressed as a percentage above (-) or below (+) the recommended safety standard of 300 g . The results indicate that the force absorption characteristics of the helmets showed inter- and intra-helmet variations, with 14 of the 18 impact sites (66.7%) assessed meeting the recommended safety standards. Helmets 1, 2 and 4 succeeded in meeting the safety standards at all impact sites; helmets 5 and 6 both failed at the back and forehead, while helmet 3 failed at all impact sites. These differences were due to the structure and composition of the inner protective layer of the helmets. The helmets that succeeded in meeting the standards were made with a moulded polystyrene insert, a heat-formed ethylene vinyl acetate (EVA) insert, or EVA with a relatively high density that allows a minimal amount of movement of the helmet at ball impact. 相似文献
3.
Football shin guards were evaluated against a kick from a studded boot.The bending stiffness of their shells, and their response
when impacted by a stud, were assessed using finite element analysis (FEA) and determined experimentally.A test rig was constructed
with the leg muscle simulated by flexible foam, with the force distribution along the tibia and to the lateral muscle measured
using flexible force sensors.High-speed photography confirmed deformation mechanisms predicted by FEA.Load spreading from
the stud impact site correlated with the guard shell bending stiffness.The best guards use shells of complex shape to increase
their transverse bending stiffness. 相似文献
4.
Luke Wilkins David Mann Stephen Dain Thomas Hayward Peter Allen 《Journal of sports sciences》2019,37(1):13-19
The International Cricket Council recently introduced new regulations for helmets in cricket. Amongst other changes, these regulations limit batters from adjusting the gap between the peak and the grille, resulting in some controversy over whether the new helmet design reduces visibility of the ball. This study compared the visual field of individuals when wearing an old helmet that does not conform to the new regulations, and the equivalent replacement which does. The visual field of 10 male participants was tested whilst wearing an old and new helmet. The new helmet resulted in a significant reduction in the visual field of the wearer (M = 66.1 out of 76 points seen in the new helmet vs. 74.8 seen with the old helmet), with the restriction predominantly confined to the superior visual field. The new regulations do appear to restrict the visual field of batters, confirming the anecdotal reports of players. However, the majority of this restriction occurs in the superior field, suggesting that the impact on batting performance may be limited. The importance of considering the impact that new helmet regulations can have on vision, batting performance, and player safety is discussed. 相似文献
5.
篮球运动中连续起跳对篮板球的作用 总被引：2，自引：0，他引：2
篮球竞赛中,抢得篮板球是获得控球权的重要手段,是双方攻守转换的焦点,是增加进攻次数的、发动快攻的重要保证,而篮板球取决于制空权的掌握,制空权又不仅仅在于对空间高度的控制,更在于对高度控制的持续时间上,因而连续起跳就显得颇为重要;本文就篮球运动中连续起跳对篮板球的作用作出理论参考。 相似文献
6.
The sweet spot of a cricket bat for low speed impacts 总被引：2，自引：1，他引：1
Rob Bower 《Sports Engineering》2012,15(2):53-60
The impact location of a cricket ball on a cricket bat has a large influence on the resulting rebound velocity of the ball. To measure this, a cricket bat was swung in a pendulum motion towards a cricket ball suspended in space. The position of the ball was modified so that it impacted the bat at 24 different positions on the face of the bat. This included six positions longitudinally and four positions laterally. The speed of the bat and each rebound were measured by a radar gun so that the apparent coefficient of restitution (ACOR) could be calculated. Impacts occurring centrally and 1?cm either side of the midline produced significantly higher rebound speeds and ACOR??s than impacts occurring 2 and 3cm off centre (p?<?0.01). Impacts occurring 15?C20?cm from the base of the bat produced the highest rebound speeds (p?<?0.01) and impacts occurring 20?C30?cm from the base of the bat produced the highest ACOR values. Implications for higher speed impacts and game scenarios are discussed. 相似文献
7.
Heat transfer variations of bicycle helmets 总被引：1，自引：0，他引：1
Brühwiler PA Buyan M Huber R Bogerd CP Sznitman J Graf SF Rösgen T 《Journal of sports sciences》2006,24(9):999-1011
Bicycle helmets exhibit complex structures so as to combine impact protection with ventilation. A quantitative experimental measure of the state of the art and variations therein is a first step towards establishing principles of bicycle helmet ventilation. A thermal headform mounted in a climate-regulated wind tunnel was used to study the ventilation efficiency of 24 bicycle helmets at two wind speeds. Flow visualization in a water tunnel with a second headform demonstrated the flow patterns involved. The influence of design details such as channel length and vent placement was studied, as well as the impact of hair. Differences in heat transfer among the helmets of up to 30% (scalp) and 10% (face) were observed, with the nude headform showing the highest values. On occasion, a negative role of some vents for forced convection was demonstrated. A weak correlation was found between the projected vent cross-section and heat transfer variations when changing the head tilt angle. A simple analytical model is introduced that facilitates the understanding of forced convection phenomena. A weak correlation between exposed scalp area and heat transfer was deduced. Adding a wig reduces the heat transfer by approximately a factor of 8 in the scalp region and up to one-third for the rest of the head for a selection of the best ventilated helmets. The results suggest that there is significant optimization potential within the basic helmet structure represented in modern bicycle helmets. 相似文献
8.
The purpose of this study was to investigate the extent to which ice hockey facial protectors can decrease overall head acceleration
during blunt impacts, as well as to identify whether attenuation differences exist between visors and cages. Commercial models
of three cages and three visors were assessed. Blunt impacts were simulated, permitting the measurement of peak accelerations
(PA) within the surrogate headform. Results indicated that face protectors, in combination with helmets, substantially reduced
PA during blunt impacts within threshold safety limits (below 300g). In general, cages showed lower PA than visors. Differences
between models were also observed during repeated impacts and impact site. In conclusion, this study demonstrates that facial
protectors function beyond their role in solely preventing facial injuries, complementing the role of the helmet in attenuating
head deceleration during impact. Consequently, the utilisation of facial protectors may reduce the severity and incidence
of head injuries. 相似文献
9.
P. A. Brühwiler M. Buyan R. Huber C. P. Bogerd J. Sznitman S. F. Graf 《Journal of sports sciences》2013,31(9):999-1011
Abstract Bicycle helmets exhibit complex structures so as to combine impact protection with ventilation. A quantitative experimental measure of the state of the art and variations therein is a first step towards establishing principles of bicycle helmet ventilation. A thermal headform mounted in a climate-regulated wind tunnel was used to study the ventilation efficiency of 24 bicycle helmets at two wind speeds. Flow visualization in a water tunnel with a second headform demonstrated the flow patterns involved. The influence of design details such as channel length and vent placement was studied, as well as the impact of hair. Differences in heat transfer among the helmets of up to 30% (scalp) and 10% (face) were observed, with the nude headform showing the highest values. On occasion, a negative role of some vents for forced convection was demonstrated. A weak correlation was found between the projected vent cross-section and heat transfer variations when changing the head tilt angle. A simple analytical model is introduced that facilitates the understanding of forced convection phenomena. A weak correlation between exposed scalp area and heat transfer was deduced. Adding a wig reduces the heat transfer by approximately a factor of 8 in the scalp region and up to one-third for the rest of the head for a selection of the best ventilated helmets. The results suggest that there is significant optimization potential within the basic helmet structure represented in modern bicycle helmets. 相似文献
10.
Portus MR Farrow D 《Sports biomechanics / International Society of Biomechanics in Sports》2011,10(4):294-305
This review synthesises the biomechanical and skill acquisition/sport expertise literature focused on the skill of cricket batting. The literature is briefly reviewed and the major limitations, challenges, and suggested future research directions are outlined. This is designed to stimulate researchers to enhance the understanding of cricket batting biomechanics and skill acquisition and in turn assist cricket coaches develop efficacious batting skill development programmes. An interdisciplinary approach between biomechanists and skill acquisition specialists is advocated to further knowledge of the underlying processes and mechanisms of cricket batting expertise. Issues such as skill measurement, practice design, ball machines, skill transfer, the impact of Twenty/20 cricket, video simulation, and skill decomposition are discussed. The ProBatter ball machine systems are introduced along with suggestions for best practice approaches for coaches when designing batting skill development programmes. 相似文献
11.
邢桂福 《哈尔滨体育学院学报》2008,26(4)
采用文献资料法、录像观察法和对比分析法,对第15届世界男篮锦标赛前八强队伍的核心后卫在进攻中技术的运用特点进行分析。研究结果表明,本届世界男篮锦标赛前八强队伍的核心后卫得分手段丰富;控球时间比较长;能够抓住战机组织有效的进攻;将突破作为主要的进攻方式,能够合理的利用突破技术直接得分、造成对方犯规或者突破后助攻传球。 相似文献
12.
An overview of cricket ball swing 总被引：1，自引：0，他引：1
Rabindra D. Mehta 《Sports Engineering》2005,8(4):181-192
The aerodynamic properties of a cricket ball have intrigued cricket players and spectators for years, arguably since the advent
of the game itself. The main interest is in the fact that the ball can follow a curved flight path that may not always be
under the control of the bowler. The basic aerodynamic principles responsible for the nonlinear flight or ‘swing’ of a cricket
ball were identified decades ago and many papers have been published on the subject. Over the last 25 years or so, several
empirical investigations have also been conducted on cricket ball swing, which revealed the amount of attainable swing and
identified the parameters that affect it. Those findings are reviewed here with emphasis on phenomena such as late swing and
the effects of humidity on swing. The relatively new concept of ‘reverse swing’, how it can be achieved in practice, and the
role in it of ‘ball tampering’, are also discussed in detail. In particular, the ability of some bowlers to effectively swing
an old ball in the conventional, reverse and the newly termed ‘contrast’ swing mode is addressed. A discussion of the ‘white”
cricket ball used in the 1999 and 2003 World Cup tournaments, which supposedly possesses different swing properties compared
to a conventional red ball, is also included. This is a current overview of cricket ball swing rather than a detailed review
of all research work performed on the topic. The emphasis is on presenting scientific explanations for the various aerodynamic
phenomena that affect cricket ball swing on a cricket ground. 相似文献
13.
第14届男子篮球世锦赛中外优秀后卫队员技术运用能力的比较分析 总被引：7，自引：0，他引：7
通过临场技术统计、电视录像观察和逻辑分析,以及查阅了相关文献资料,对第14届男子篮球世锦赛中国男篮与外国男篮(前四名)优秀后卫队员技术运用的能力进行比较分析,旨在对比和寻找目前中外优秀后卫队员在技术运用能力上存在的差异。 相似文献
14.
One of the tests used to evaluate the performance of sports surfaces measures the peak deceleration of a rigid mass during
contact with the surface, after being dropped from a set height. It is widely used and is included in a number of international
standards.
The test was carried out using two drop heights on four different designs of artificial cricket pitch, with a full set of
acceleration data being collected over the duration of impact. These data were then integrated twice with respect to time
to produce velocity and displacement information. Oblique impacts of cricket balls were also carried out and analysed using
a high-speed video system to evaluate the playing performance of each pitch design.
It was found that, although the pitches gave quite different readings of peak deceleration, they produced similar values for
coefficient of restitution and were therefore considered to ‘play’ in a very similar way. This was due to a high peak deceleration
reading being accompanied by a short contact time and low peak deceleration being accompanied by a long contact time, meaning
that the change in momentum was similar in both cases. It was concluded that for accelerometer tests to be useful, all the
acceleration-time data should be analysed, rather than the peak value alone. 相似文献
15.
Sanne Cornelia Maria te Wierike Barbara Catharina Helena Huijgen Laura Jonker Chris Visscher 《Journal of sports sciences》2018,36(6):710-716
This study first investigated the importance of ball control and (self-reported) self-regulatory skills in achieving the elite level in basketball. The second aim was to gain insight into the development of, and association between ball control and (self-reported) self-regulatory skills that contribute to achieving the elite level, with taking into account positional differences. Talented male players (N = 73; age 16.56 ± 1.96) completed the STARtest to measure ball control and a questionnaire to measure (self-reported) self-regulation from 2008–2012. Results showed that (self-reported) reflective skills were most important to achieve the elite level (OR = 11.76; P < 0.05). There was no significant improvement in (self-reported) reflection over time for guards, forwards, and centers. Improvement in ball control was evident for guards (r = ?0.65; P < 0.05). Furthermore, guards and forwards had better ball control compared to centers (P < 0.01). For those two positions, negative correlations were found between (self-reported) reflection and ball control, i.e., higher reflection was related to better ball control (guards r = ?0.19; forwards r = ?0.18) in contrast to centers (r = 0.34). It is concluded that (self-reported) reflective skills are important to achieve the elite level, while ball control seems especially important for guards. 相似文献
16.
运用文献法、观察法、数理统计法等方法对第29界奥运会中国男篮后卫和前4强队后卫攻防技术进行对比分析。结果显示：在防守方面,封盖和犯规略占优势,抢断则存在显著性差异。在进攻方面,失误次数和罚球命中率占有优势,在2分出手次数、命中次数以及2分球和3分球命中率方面存在显著性差异。另外,在进攻篮板球方面和场均贡献率方面也存在显著性差异。 相似文献
17.
New cricket bats need to be ‘knocked in’ prior to use, but just what this process does to the surface fibres of the bat is
unknown and unquantified. One quantitative measurement of knock-in is the resultant surface hardness of the bat, and this
paper describes knock-in tests to determine the surface hardness following differing durations of knock-in. The design of
a cricket bat knock-in machine is first described. This takes the form of a cradle in which a cricket bat can be secured horizontally
and then traversed at constant speeds in two mutually perpendicular directions while at the same time being struck with constant
force by a cricket ball. The traverses are driven by lead screws, the motors of which can be independently switched on or
off. The traverse distance can be varied with adjustable limit switches and relays that reverse the direction of rotation
of the lead screws when activated. The cricket ball is attached to a rod that is lifted cyclically by a cam against a coil
spring extension, and then allowed to fall under that force to impact on the bat surface. The impact (knocking-in) force was
measured by a previously calibrated strain gauge attached to the rod holding the cricket ball. By judicious setting of the
limit switches, selected areas of the bat surface were continuously knocked in for periods varying from 1 to 4 hours. After
knocking in, the surface hardness was measured in accordance with British Standard 373 using a penetrator designed in accordance
with the same standard. Analysis of the load/penetration curves shows an increase in surface hardness with knock duration.
Photographs of the cell structure of the surface wood, obtained using a scanning electron microscope, show that under knock-in
conditions, the wood cells collapse to form a mesh-like hardened layer which increases in hardness with increase in knock-in
duration. 相似文献
18.
The surface on to which a bowler projects a ball in the game of cricket is made up of hard packed soil with sparse grass cover.
This natural turf pitch is of fundamental importance to the play of the game and the quality of the surface is a prime concern
of players, officials, commentators and spectators alike. A programme of research has been undertaken to identify the factors
that lead to the construction of high quality cricket pitches. This work employed the technology of highspeed video analysis
to monitor the performance of first class cricket pitches during county matches. A system for measuring the impact of a cricket
ball on a pitch was developed, and over 3000 ball impacts analysed. This analysis enabled pitches to be characterized in terms
of pace, bounce and consistency. Soil properties for the monitored pitches were identified and correlations were drawn between
pitch performance and soil composition. 相似文献
19.
Elizabeth N. Kuhn Joseph H. Miller Blake Feltman Alexander K. Powers Dean Sicking James M. JohnstonJr. 《Sports Engineering》2017,20(1):29-40
Concussion awareness in youth sports has increased secondary to recent legislation, public health campaigns, and media coverage. The potential for long-term negative sequelae is now widely recognized and there have been a number of initiatives nationwide to prevent pediatric head injuries, including efforts to design more effective helmets for repetitive impact sports. The primary aim of this review is to systematically assess the literature regarding helmet design in youth sports specifically designed to mitigate repetitive low- and medium-energy impacts. Secondary aims include identifying areas for future research and opportunities for helmet design improvement. A systematic review of the literature was performed to identify articles relating to youth helmet design and biomechanical studies of concussion in youth sports. Pubmed, Google scholar, Cochrane Review and article citations were used to identify all pertinent English articles between 1971 and January 2016. A total of 14 studies met criteria for inclusion in this review, three of which included clinical outcomes (all Level of Evidence II) and eleven of which included biomechanical outcomes. The vast majority focused on adolescents playing football. Six of the biomechanical studies demonstrated improved biomechanical metrics in helmets with increasing foam thickness and number of foam layers. Two clinical studies also seem to support this concept, with significant caveats. To date, there are limited clinical and biomechanical data on youth helmet design. There is a need for further research in order to optimize helmet design and reduce the number and severity of pediatric sports-related head injuries. 相似文献
20.
Modern-day cricket has experienced a shift towards limited over games, where the emphasis is on scoring runs at a rapid rate. Although the use of protective equipment in cricket is mandatory, players perceive that leg guards, in particular, can restrict their motion. The aim of this study was to determine the influence of cricket leg guards on running performance. Initial testing revealed that wearing pads significantly increased the total time taken to complete three runs by up to 0.5?s compared with running without pads (P?相似文献