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1.
运用文献资料、专家访谈、问卷调查等方法,对当前江苏省高校慢投垒球运动的开课情况、场地设施、师资情况、经费情况、竞赛情况与开展的现状进行调查分析,并提出相应的发展对策,为江苏省高校慢投垒球运动的推广和普及提供依据。  相似文献   

2.
Abstract

Four sprint starting positions—the bunch, medium, elongated, and hyperextended—were compared on mean elapsed times at distances of 10 and 30 yd. Averages of three starts for each of 30 inexperienced college undergraduate males on each type of start were derived from electronically-controlled measures, the times for both distances being recorded from the same start. Statistical analyses indicated significantly lower elapsed times with the hyperextended starting position.  相似文献   

3.
通过文献资料法、专家访谈法、问卷调查法、数理统计法等对江苏省高校慢投垒球课程教师基本情况调查与研究,结果表明:江苏省高校慢投垒球教师队伍以男性教师为主,年龄上趋于年轻化,具有研究生学历、讲师为多数,教龄普遍不长,专业慢投垒球教师较缺乏,专项运动等级水平不高,基本上接受过各种各样短期培训;教学目标明确,教学内容较多,教学过程中虽然采取多元教学方法,但缺乏传统与创新教学手段的融合,缺乏实战,科研能力较弱,急需提升。  相似文献   

4.
Softballs     
There is currently much debate about the safety of the sport of softball. Batted‐ball speed and average pitcher reaction time are factors often used to determine safe performance. Batted‐ball speed is shown to be the most important factor to consider when determining safe play. Average pitcher reaction time is explained and directly correlated to batted‐ball speed. Eleven aluminum multi‐wall, three aluminum single‐wall and two composite softball bats were tested with mid‐compression polyurethane softballs averaging 1721 ±62 N/6.4 mm to represent the relative bat‐ball performance for the sport of slow‐pitch softball. Nine men and six women were chosen for this study out of a test group of over three hundred slowpitch softball players. On average, aluminum bat performance results were within the recommended safety limits established by the national softball associations. However, when composite bats were used, their performance results exceeded the recommended safety limits which can pose a significant safety risk. Using aluminum softball bats, batted‐ball speeds ranged from 80 to 145 km.h‐1. Using composite softball bats, batted‐ball speeds ranged from 146 to 161 km.h‐1. The scientific relevance of this study is to provide performance information that can lead to injury prevention in the sport of softball.  相似文献   

5.
Starting block performance in swimming is of crucial importance in the individual competitions for the shorter swimming distances as well as for the relay events. The significance of this swim start performance will increase with the introduction of a new starting block with a longer and slightly steeper surface in conjunction with a push-off support for the feet and laterally adjustable handles. As grab starts and track starts were equally observed in international swimming competitions there are good reasons to assume that only the latter will remain the dominant starting technique. This report aims to summarize existing knowledge on the biomechanics of the swim start performed on a traditional starting block as a new starting block is introduced and new starting techniques are going to be developed. Following some introductory remarks on the assessment of the swim start performance, results will be discussed on the merit of different take-off techniques, on the entry behaviour, and on the force development profiles on the starting block. In conclusion, a tendency in favour of the rear-weighted track start was found in conjunction with a flat entry. In addition, it could be shown that an angular momentum around the transverse body axis combined with a dolphin kick (and a previously hyperextended hip joint) may provide hydrodynamic conditions to enter the water with a rather steep centre of mass trajectory. Finally, existing biomechanical knowledge will be presented on the relay start as well as on a possible change in the starting technique using the new block.  相似文献   

6.
Joint moments can be used as an indicator of joint loading and have potential application for sports performance and injury prevention. The effects of changing walking and running speeds on joint moments for the different planes of motion still are debatable. Here, we compared knee and ankle moments during walking and running at different speeds. Data were collected from 11 recreational male runners to determine knee and ankle joint moments during different conditions. Conditions include walking at a comfortable speed (self-selected pacing), fast walking (fastest speed possible), slow running (speed corresponding to 30% slower than running) and running (at 4 m · s?1 ± 10%). A different joint moment pattern was observed between walking and running. We observed a general increase in joint load for sagittal and frontal planes as speed increased, while the effects of speed were not clear in the transverse plane moments. Although differences tend to be more pronounced when gait changed from walking to running, the peak moments, in general, increased when speed increased from comfortable walking to fast walking and from slow running to running mainly in the sagittal and frontal planes. Knee flexion moment was higher in walking than in running due to larger knee extension. Results suggest caution when recommending walking over running in an attempt to reduce knee joint loading. The different effects of speed increments during walking and running should be considered with regard to the prevention of injuries and for rehabilitation purposes.  相似文献   

7.
孙丽萍 《浙江体育科学》2005,27(3):46-49,94
采用动态分析法、数据统计法、并列因素分析法对世界优秀女子400m跑运动员的速度分配进行分析统计.结果表明,8个50m分段的标准差越小,匀速跑的能力越强,前3名选手都有较强的匀速跑能力,最快和最慢50m分段的时间差与运动成绩显著相关,延长加速时间有利于全程的速度分配;通过分析第1名的分段时间与2～8名的分段时间发现,第1名运动员启动速度较快,第2分段控制速度,在第5、6分段速度优势明显.  相似文献   

8.
Abstract

The sprint starts of 12 skilled collegiate sprinter!hurdlers were filmed for four different sprint start conditions. Ground reaction forces were collected for the first step out of the blocks and velocities through a 2-m speed trap immediately following the first support phase were recorded. The subjects employed their preferred right-left leg placement in the blocks, while the anterior–posterior spacing of the front block with respect to the starting line and the amount of forward lean in the set position were varied. Four positions were constructed that accounted for anthropometric differences. The four positions consisted of combinations of two arm orientations (forward lean and perpendicular to ground) and two front block to starting line distances (bunched and elongated). Kinematic data were reduced to provide center of mass position and velocity measures and analyzed for critical periods throughout the starting action. Selected critical events from the first step kinetic records were also analyzed. The results indicated that the elongated starting positions resulted in greater horizontal displacement, greater propelling impulse, increased first step toe-off velocity, and greater average velocity through a 2-m speed trap. Arm orientation effects were less well defined. Forward lean tended to result in greater vertical velocity at block clearance and horizontal velocity at first step toe-off, whereas perpendicular arm positioning resulted in greater 2-m speed trap velocity.  相似文献   

9.
BackgroundRunning is becoming an increasingly popular activity among Americans with over 50 million participants. Running shoe research and technology has continued to advance with no decrease in overall running injury rates. A growing group of runners are making the choice to try the minimal or barefoot running styles of the pre-modern running shoe era. There is some evidence of decreased forces and torques on the lower extremities with barefoot running, but no clear data regarding how this corresponds with injuries. The purpose of this survey study was to examine factors related to performance and injury in runners who have tried barefoot running.MethodsThe University of Virginia Center for Endurance Sport created a 10-question survey regarding barefoot running that was posted on a variety of running blogs and Facebook pages. Percentages were calculated for each question across all surveys. Five hundred and nine participants responded with over 93% of them incorporating some type of barefoot running into their weekly mileage.ResultsA majority of the participants (53%) viewed barefoot running as a training tool to improve specific aspects of their running. However, close to half (46%) viewed barefoot training as a viable alternative to shoes for logging their miles. A large portion of runners initially tried barefoot running due to the promise of improved efficiency (60%), an attempt to get past injury (53%) and/or the recent media hype around the practice (52%). A large majority (68%) of runners participating in the study experienced no new injuries after starting barefoot running. In fact, most respondents (69%) actually had their previous injuries go away after starting barefoot running. Runners responded that their previous knee (46%), foot (19%), ankle (17%), hip (14%), and low back (14%) injuries all proceeded to improve after starting barefoot running.ConclusionPrior studies have found that barefoot running often changes biomechanics compared to shod running with a hypothesized relationship of decreased injuries. This paper reports the result of a survey of 509 runners. The results suggest that a large percentage of this sample of runners experienced benefits or no serious harm from transitioning to barefoot or minimal shoe running.  相似文献   

10.
The simple auditory reaction time is one of the fastest reaction times and is thought to be rarely less than 100 ms. The current false start criterion in a sprint used by the International Association of Athletics Federations is based on this assumed auditory reaction time of 100 ms. However, there is evidence, both anecdotal and from reflex research, that simple auditory reaction times of less than 100 ms can be achieved. Reaction time in nine athletes performing sprint starts in four conditions was measured using starting blocks instrumented with piezoelectric force transducers in each footplate that were synchronized with the starting signal. Only three conditions were used to calculate reaction times. The pre-motor and pseudo-motor time for two athletes were also measured across 13 muscles using surface electromyography (EMG) synchronized with the rest of the system. Five of the athletes had mean reaction times of less than 100 ms in at least one condition and 20% of all starts in the first two conditions had a reaction time of less than 100 ms. The results demonstrate that the neuromuscular-physiological component of simple auditory reaction times can be under 85 ms and that EMG latencies can be under 60 ms.  相似文献   

11.
Abstract

A number of studies have investigated effects of speed on local dynamic stability of walking, although this relationship has been rarely investigated under changing task constraints, such as during forward and backward running. To rectify this gap in the literature, the aim of this study was to investigate the effect of running speed on local dynamic stability of forward and backward running on a treadmill. Fifteen healthy male participants took part in this study. Participants ran in forward and backward directions at speeds of 80%, 100% and 120% of their preferred running speed. The three-dimensional motion of a C7 marker was recorded using a motion capture system. Local dynamic stability of the marker was quantified using short- and long-term largest finite-time Lyapunov exponents (LyE). Results showed that short-term largest finite-time LyE values increased with participant speed meaning that local dynamic stability decreased with increasing speed. Long-term largest finite-time LyEs, however, remained unaffected as speed increased. Results of this study indicated that, as in walking, slow running is more stable than fast running. These findings improve understanding of how stability is regulated when constraints on the speed of movements is altered. Implications for the design of rehabilitation or sport practice programmes suggest how task constraints could be manipulated to facilitate adaptations in locomotion stability during athletic training.  相似文献   

12.
The present study was designed to analyse and compare the kinetics and kinematics associated with three different starting strategies during classic cross-country ski racing. Inside a ski tunnel, 12 elite male skiers performed three sets of three 38?m starts. Each set included one start using: double poling only (DP), diagonal stride only (DIA) and freely chosen (FREE) (i.e. where subjects used the strategy or combination of strategies they felt was fastest) in random order. The first 18?m was performed on a series of force plates that measured horizontal and vertical forces followed by 20?m of a standard snow track. Additionally, cycle characteristics and joint angles were measured. DIA and FREE were faster over 38?m than DP (P?.01). Net horizontal impulse (taking into account both positive and negative impulses) 5–10?m after the start was lower during DP than during DIA and FREE (both P?<?.05). All subjects skied faster when using only DIA for the entire 38?m. Furthermore, the sum duration and frequency of propulsive contacts over the first 18?m was less in DP than DIA and FREE (P?相似文献   

13.
Abstract

Several researchers have demonstrated that an external focus of attention (about movement’s effects) during movement execution allowed better performances and learning of various motor tasks than an internal focus of attention (about movement itself). However, attentional focus effects have not been studied in tasks requiring explosive actions preceded by fast reaction time to a signal, such as a sprint start. We hypothesised that the beneficial effect of external focus of attention would be observed in the different stages of the sprint start (i.e. reaction time, block clearance and running) for both expert and novice sprinters. Novice and expert sprinters performed sprint starts followed by a 10 m sprint under three conditions: external focus instructions; internal focus instructions; and neutral instructions. The reaction time and the running time were significantly shorter in the external focus condition than in the internal focus condition, for both expert and novice participants. These results confirm the beneficial effect of an external focus of attention on the speed of movement execution. Moreover, they revealed that attentional focus influences movement preparation. Several hypotheses are proposed to account for these results, with reference to the processes that could be responsible for the observed effects.  相似文献   

14.
Abstract

The aims of the present study were to examine quantitatively ground reaction forces, kinematics, and muscle activations during the windmill softball pitch, and to determine relationships between knee valgus and muscle activations, ball velocity and muscle activation as well as ball velocity and ground reaction forces. It was hypothesized that there would be an inverse relationship between degree of knee valgus and muscle activation, a direct relationship between ground reaction forces and ball velocity, and non-stride leg muscle activations and ball velocity. Ten female windmill softball pitchers (age 17.6 ± 3.47 years, stature 1.67 ± 0.07 m, weight 67.4 ± 12.2 kg) participated. Dependent variables were ball velocity, surface electromyographic (sEMG), kinematic, and kinetic data while the participant was the independent variable. Stride foot contact reported peak vertical forces of 179% body weight. There were positive relationships between ball velocity and ground reaction force (r = 0.758, n = 10, P = 0.029) as well as ball velocity and non-stride leg gluteus maximus (r = 0.851, n = 10, P = 0.007) and medius (r = 0.760, n = 10, P = 0.029) muscle activity, while there was no notable relationship between knee valgus and muscle activation. As the windmill softball pitcher increased ball velocity, her vertical ground reaction forces also increased. Proper conditioning of the lumbopelvic–hip complex, including the gluteals, is essential for injury prevention. From the data presented, it is evident that bilateral strength and conditioning of the gluteal muscle group is salient in the windmill softball pitch as an attempt to decrease incidence of injury.  相似文献   

15.
Abstract

This study aimed to understand the kinematic and kinetic differences between two sprint starts: block and split-stance standing. Fourteen sub-elite male sprinters (100 m time: 11.40?±?0.39?s) performed block and split-stance standing starts sprints over 30 m of in-ground force platforms in a randomised order. Independent t-tests and repeated measures mixed model analysis of variance were used to analyse the between-condition variables across conditions, and over four step phases. Block start sprints resulted in significantly (p?<?.05) faster 5 m (5.0%, effect size [ES]?=?0.89) and 10?m (3.5%, ES?=?0.82) times, but no significant differences were found at 20 and 30?m. No significant differences were found in any kinematic measure between starting positions. However, block starts resulted in significantly (p?<?.001) greater propulsive impulses (6.8%, ES?=?1.35) and net anterior-posterior impulses (6.5%, ES?=?1.12) during steps 1–4, compared to the standing start. Block starts enable athletes to produce a greater amount of net anterior-posterior impulse during early accelerated sprinting, resulting in faster times up to 10 m. When seeking to improve initial acceleration performance, practitioners may wish to train athletes from a block start to improve horizontal force production.  相似文献   

16.
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   

17.
Abstract

The catcher has the most demanding position in the games of baseball and softball with no regulations on how many throws they make during game. It was the purpose of this study to describe the kinematics and kinetics of the throwing motion in catchers when throwing down to second base. It was hypothesised that younger and older catchers would display significantly different throwing kinematics and kinetics. Thirty-eight baseball and softball catchers volunteered to participate. Twenty participants were considered younger (aged 9–14, 10.95 ± 1.76 years, 151.11 ± 15.64 cm, 47.94 ± 18.84 kg) and 18 were deemed the older group (aged 15–23, 18.11 ± 2.61 years, 170.91 ± 8.67 cm, 74.88 ± 10.74 kg). Participants received a pitch and completed five accurate throws to second base in full catching gear. The average ball speed of the older catchers was 21 ± 3.58 meters per second (47 ± 8.02 mph) while the younger catchers averaged 17.2 ± 4.0 meters per second (38.6 ± 8.96 mph). Older catchers had greater shoulder elevation at ball release and significantly greater shoulder external rotation at foot contact and shoulder maximum external rotation than younger catchers. It is clear that chronological age plays a role in the throwing mechanics observed in catchers throwing down to second base, however the effects of these differences are not fully understood (i.e., skeletal maturity, experience, strength).  相似文献   

18.
Abstract

The purpose of this study was to examine relative timing, relative distance, and effector independence characteristics of the triple jump. We videotaped expert and novice triple jumpers using standing and running starts. On some trials, the triple jumpers were required to take off from their nondominant leg. Gentner's (1987) interaction test was used to assess the proportional duration model in describing the timing of the component submovements. For both experts and novices, the proportional durations varied with the type of start. For experts, the relative timing of the jump components was independent of the take-off leg. The findings were mixed for the novices. Similar results were obtained when relative distance was examined. These results are discussed with respect to constructs related to variability in skilled performance.  相似文献   

19.
The aims of the present study were to examine quantitatively ground reaction forces, kinematics, and muscle activations during the windmill softball pitch, and to determine relationships between knee valgus and muscle activations, ball velocity and muscle activation as well as ball velocity and ground reaction forces. It was hypothesized that there would be an inverse relationship between degree of knee valgus and muscle activation, a direct relationship between ground reaction forces and ball velocity, and non-stride leg muscle activations and ball velocity. Ten female windmill softball pitchers (age 17.6 ± 3.47 years, stature 1.67 ± 0.07 m, weight 67.4 ± 12.2 kg) participated. Dependent variables were ball velocity, surface electromyographic (sEMG), kinematic, and kinetic data while the participant was the independent variable. Stride foot contact reported peak vertical forces of 179% body weight. There were positive relationships between ball velocity and ground reaction force (r = 0.758, n = 10, P = 0.029) as well as ball velocity and non-stride leg gluteus maximus (r = 0.851, n = 10, P = 0.007) and medius (r = 0.760, n = 10, P = 0.029) muscle activity, while there was no notable relationship between knee valgus and muscle activation. As the windmill softball pitcher increased ball velocity, her vertical ground reaction forces also increased. Proper conditioning of the lumbopelvic-hip complex, including the gluteals, is essential for injury prevention. From the data presented, it is evident that bilateral strength and conditioning of the gluteal muscle group is salient in the windmill softball pitch as an attempt to decrease incidence of injury.  相似文献   

20.
贾昌志 《浙江体育科学》2007,29(5):41-43,54
运用文献资料法对当今世界女子中长跑的比赛特点和训练发展趋势进行对比分析,认为当今女子中长跑的比赛是两头快中间稍慢的速度节奏特点,训练发展趋势是以速度为核心的大强度训练。我国女子中长跑运动员在比赛速度节奏的把握和最后的冲刺速度能力上与国外运动员有一定的差距,与此同时也为我国女子中长跑今后的训练提出了合理性建议。  相似文献   

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