The effects of dynamic and static stretching methods on speed, agility and power

INTRODUCTION: Warm-ups are integral to coaches’ and athletes’ preparations, yet current research and practice provides conflicting advice on the most effective warm-up procedure for aiding performance. The value of a warm-up is not in question but the role of static stretching within the warm-up is contentious. A number of studies have suggested that static stretching is detrimental to performance (Shrier, 2004), though these have not always employed stretching protocols that reflect those actually used by performers. Many athletes continue to include static stretching as part of their routine, often following a dynamic warm-up. The purpose of the study was to investigate, using realistic protocols, the effects on speed, agility and power of additional static stretching following a dynamic warm-up. METHOD: To date 16 University sports students (11 male, 5 female) have been recruited to the study, which was approved by the University ethics commitee. Following familiarisation with the warm-up methods and sports performance measures, all participants performed two warm-up protocols one week apart. The protocols concentrated on the quadriceps, hamstrings, gastrocnemius, soleus, gluteals, adductors and hip flexors. The Dynamic Warm-up (DW) protocol used a series of specific progresive exercises lasting 10 minutes over a distance of 20m with a jog recovery. The Dynamic Warm-up plus Static Stretching (DWS) protocol used the same DW protocol followed by a 5 minute period during which 7 stretches were held at a point of moderate discomfort for 20 seconds. After an intial rest period of 2 minutes the subjects performed a countermovement vertical jump (CMJ), 20m sprint and Illinios agility test. A one minute rest period was used between performance measures to mimic competitive performance. The order the performance measures were conducted were randomised for each subject; for an individual subject the order was maintained for both protocols. Paired t-tests were used to identify differences between the 3 performance measures over the two warm-up protocols, with a significance level of p ≤ 0.05. RESULTS & DISCUSSION: 20m sprint performance was significantly reduced (p=0.03) by the use of the DWS protocol (3.4 ± 0.32s, mean ± SD) when compared to DW only (3.29 ± 0.29s). The CMJ (DW =0.51 ± 0.09m vs DWS =0.48 ± 0.09m) and Illinois agility (DW =17.31 ±1.0s vs DWS =17.37 ±1.04s) performance showed no significant difference with the addition of static stretching. Previous studies have used static stretching for periods in excess of levels used in conventional warm-ups but the present study indicates that static stretching for as little as 20 seconds after a dynamic warm-up can reduce 20m sprinting performance. Possible mechanisms for this include a decrease in the stiffness of the musculotendinous unit and an acute neural inhibition leading to a decrease in muscle activation levels (Young, 2007). CONCLUSION: The use of static stretching following a dynamic warm-up decreased sprinting performance compared with the dynamic warm-up alone. Practitioners and athletes should use static stretching prior to performance with caution

The effect of plyometric training on handspring vault performance in adolescent female gymnasts

Purpose: Despite the huge amount of force exerted by both the upper and lower extremity musculature in gymnastic vaulting, there is scant research investigating the benefits that plyometric training can induce. The handspring vault is of paramount importance for a gymnast’s vaulting development, and requires both technical skill and power production to achieve success. The aim of this study was to determine the effects that plyometric training can have when added to habitual training on handspring vault performance variables in female adolescent gymnasts. Methods: Twenty female competitive gymnasts (mean ± SD: age 12.5 ± 1.7 years; stature 1.46 ± 0.11 m; mass 40.5kg ± 9.7 kg) volunteered to partake in this study. Participants were randomly assigned to two independent groups. The experimental plyometric training group (PT) pursued a six-week plyometric program, consisting of two additional 45 minute sessions a week, alongside their habitual training. The control group (CG) continued their regular habitual training only. Videography was used (120 Hz) in the sagittal plane, both pre and post training intervention, to assess key performance indicators attributed to the technical performance and competence required to execute a successful handspring vault. In addition, participants completed a countermovement vertical jump (CMJ) as an assessment of lower body power. Results: Significant improvements (P < 0.05) were found for the PT in comparison to CG for run-up velocity, take-off velocity, distance from take-off to springboard, duration of foot contact on board, duration of hand contact on vault, duration of post flight and CMJ height. However, no significant differences were found between groups for first flight time, shoulder angle or hip angle on the vault. Furthermore, the CG demonstrated no significant improvement for handspring vault measures or CMJ height. Conclusions: The results demonstrated that the implementation of plyometric training led to improvements of several key variables which are associated to successful handspring vault performance. It can be suggested that implementing plyometric training can improve handspring vault performance in adolescents, appropriately preparing gymnasts for the development and progression of vaulting in the future

Trends in Olympic and Commonwealth games records for throwing events

Throwing events have been an integral part of the track and field program in both Olympic and Commonwealth Games since their inception. Most scientific studies of these events have concentrated on biomechanical analysis or the physical capacity requirements of the athletes. This paper examines and compares the trends over time of the gold medal results of three throwing events in the Olympics and the Commonwealth Games for male competitors. Data was collected from the ‘Athletic’s Almanac’ web-site, for the period since inception of these games until the present day. The data was examined to identify the linear trends that exist for all three events. Similarities between results in the shot-put and hammer of a steady increase in distances thrown over time were evident. Whereas, the discus records showed a steeper positive relationship over time. In addition, critical world-wide incidents, trends in social expectations and increase in sports science and technical knowledge were concluded to have an effect on the results of these athletic pursuits in terms of acceleration periods and plateaus of results. In summary, trends in general for records in these throwing events showed a steady rise from the outset of competition until the late 1960s to early 1970s. Since this period, there has been considerable tapering off of improvements in distances achieved. These trends were seen in both the Olympic Games and the Commonwealth Games

Reproducibility of speed, agility and power assessments in elite academy footballers

Purpose: Fitness testing is a visible part of many youth and senior football programs (Pyne et al. 2014). A high priority is given to physical assessments that relate to the demands of match performance (Rampinini et al. 2007). However somewhat surprisingly, the reproducibility of common assessments using elite football cohorts are not widely reported in the literature (Pyne et al. 2014). Field test assessments of speed, agility and power not only provide an indicator of sport-specific power producing ability but can also be used for diagnostic purposes to identify whether an athlete is suffering from fatigue, functional / non-functional overreaching or overtraining (Meeusen et al. 2013). The purpose of this study was to ascertain the reproducibility of testing protocols used to monitor speed, agility and power capabilities within elite academy footballers. Methods: Ten male apprentice professional football players (mean ± SD: age = 17.1 ± 0.7 years, stature = 1.83 ± 0.09 m, mass: 77.8 ± 8.2 kg) participated in the study. All participants completed three separate identical trials with a day’s recovery interspersed between each trial. Each trial consisted of the following assessments; a countermovement jump test (CMJ), a seated medicine ball throw test (Throw), a 40 m run sprint test (40 m), which incorporated a 0-10 m assessed phase (10 m) and the arrowhead agility test (Agility). Results: Findings from One-way ANOVA tests indicated that performance was unchanged across the three trials for all assessments (P > 0.05). Mean typical error as a percentage (TE %) [90 % confidence intervals (CI)] across the assessments indicated highly acceptable reproducibility; CMJ = 3.2% (2.5-4.7), Throw = 1.4% (1.0-2.0). 10 m = 1.6% (1.3-2.4), 40m = 1.4% (1.1-2.0), Agility = 0.9% (0.7-1.3). Conclusion: Elite academy footballers were found to have consistent performance for assessments of speed, agility and power across three trials. Typical error was found to be low for all assessments indicating a high level of reproducibility across repeated trials (Hopkins et al. 2001). Therefore, these assessments can be confidently used in the physical fitness monitoring of elite academy footballers

A practical approach to object based requirements analysis

Presented here is an approach developed at the Unisys Houston Operation Division, which supports the early identification of objects. This domain oriented analysis and development concept is based on entity relationship modeling and object data flow diagrams. These modeling techniques, based on the GOOD methodology developed at the Goddard Space Flight Center, support the translation of requirements into objects which represent the real-world problem domain. The goal is to establish a solid foundation of understanding before design begins, thereby giving greater assurance that the system will do what is desired by the customer. The transition from requirements to object oriented design is also promoted by having requirements described in terms of objects. Presented is a five step process by which objects are identified from the requirements to create a problem definition model. This process involves establishing a base line requirements list from which an object data flow diagram can be created. Entity-relationship modeling is used to facilitate the identification of objects from the requirements. An example is given of how semantic modeling may be used to improve the entity-relationship model and a brief discussion on how this approach might be used in a large scale development effort

SENSITIVITY TO SCOPE: EVIDENCE FROM A CVM STUDY OF WETLANDS

Wetlands valuation is a situation in which CVM studies might be expected to fail scope tests. This paper reports results from a split-sample CVM study of Wisconsin wetlands. The survey employed a multiple-bounded, polychotomous-choice format, and compared WTP distributions using the method of convolutions. The survey demonstrated sensitivity to scope.Resource /Energy Economics and Policy,

El sistema Archéo DATA: hacia la creación de un Sistema de Información Arqueológica

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Iris Recognition: The Consequences of Image Compression

Iris recognition for human identification is one of the most accurate biometrics, and its employment is expanding globally. The use of portable iris systems, particularly in law enforcement applications, is growing. In many of these applications, the portable device may be required to transmit an iris image or template over a narrow-bandwidth communication channel. Typically, a full resolution image (e.g., VGA) is desired to ensure sufficient pixels across the iris to be confident of accurate recognition results. To minimize the time to transmit a large amount of data over a narrow-bandwidth communication channel, image compression can be used to reduce the file size of the iris image. In other applications, such as the Registered Traveler program, an entire iris image is stored on a smart card, but only 4 kB is allowed for the iris image. For this type of application, image compression is also the solution. This paper investigates the effects of image compression on recognition system performance using a commercial version of the Daugman iris2pi algorithm along with JPEG-2000 compression, and links these to image quality. Using the ICE 2005 iris database, we find that even in the face of significant compression, recognition performance is minimally affected

A multicomponential examination of tennis players’ emotional responses to music

This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.The principal aim of this research programme was to examine multiple components of competitive tennis players’ emotional responses to pre-performance music. To this end, four objectives were defined: First, to develop a grounded theory (Glaser & Strauss, 1967) of players’ use of music to manipulate emotional state; second, to examine the impact of altering music tempo and intensity on players’ affective and behavioural responses; third, to identify neural origins for these phenomena; and fourth, to elucidate the role of motoneuron excitability in behavioural responses observed. These objectives were realised in four interrelated studies. First, 14 players provided quantitative and qualitative interview, questionnaire, and diary data to detail their use of personally emotive music; a grounded theory and associated model were consequently developed to facilitate future research and practice. Participants used music to attain five broad emotional states, including psyched-up; this was associated with faster tempi and louder intensities (volumes). Study 2 was conceived to examine the effects of manipulating these variables on 54 players’ affective and behavioural states, using measures based on Russell’s (1980) affective circumplex and reaction times (RTs). Faster tempi elicited higher valence and arousal, loud intensity yielded higher arousal and shorter RTs; and higher arousal was associated with shorter RTs. Functional magnetic resonance imaging was utilised in Study 3 to identify neural bases for 12 participants’ emotional responses to the same music manipulations; emotion-processing, visuomotor and sensorimotor structures were activated under high-arousal conditions. Transcranial magnetic stimulation and electromyography were used in Study 4 to investigate changes in 10 participants’ corticospinal excitability as a result of listening to purposively selected music; optimised music elicited higher arousal and reduced corticospinal response latencies. The foremost contribution of this thesis is to show that music variables may be carefully selected and/or manipulated to maximise performance-facilitating emotional responses to music in tennis