The dynamic viscoelastic characterisation of the impact behaviour of the GAA sliotar

In recent years variability in behaviour of the sliotar, a small leather-bound ball used in the Irish sport of hurling, became evident in championship matches. The current standard has not provided adequate repeatability of ball performance. A new method for assessing the dynamic impact behaviour of approved sliotar cores has been characterised. This test system was developed to measure the performance characteristics, such as coefficient of restitution, deformation and contact time, and the viscoelastic properties of dynamic stiffness and hysteresis energy dissipation. In this paper, the relationship between the viscoelastic properties and the coefficient of restitution is presented

Discrete vs. functional based data to analyze countermovement jump performance

While discrete point analysis (DPA) (e.g. peak power) is by far the most common method of analyzing movement data, it may have significant limitations because it ignores the vast majority of a signal’s data. In response, there has been a small but growing use of methods, such as functional data analysis (FDA), which allow an investigation of the underlying structure of the continuous signal and may therefore provide a more powerful analysis. However, a direct comparison between DPA and FDA has not been previously reported

A virtual coaching environment for improving golf swing technique

As a proficient golf swing is a key element of success in golf, many golfers make significant effort improving their stroke mechanics. In order to help enhance golfing performance, it is important to identify the performance determining factors within the full golf swing. In addition, explicit instructions on specific features in stroke technique requiring alterations must be imparted to the player in an unambiguous and intuitive manner. However, these two objectives are difficult to achieve due to the subjective nature of traditional coaching techniques and the predominantly implicit knowledge players have of their movements. In this work, we have developed a set of visualisation and analysis tools for use in a virtual golf coaching environment. In this virtual coaching studio, the analysis tools allow for specific areas require improvement in a player's 3D stroke dynamics to be isolated. An interactive 3D virtual coaching environment then allows detailed and unambiguous coaching information to be visually imparted back to the player via the use of two virtual human avatars; the first mimics the movements performed by the player; the second takes the role of a virtual coach, performing ideal stroke movement dynamics. The potential of the coaching tool is highlighted in its use by sports science researchers in the evaluation of competing approaches for calculating the X-Factor, a significant performance determining factor for hitting distance in a golf swing

Biomechanical factors associated with jump height: a comparison of cross-sectional and pre-to-post training change findings

Previous studies investigating the biomechanical factors associated with maximal countermovement jump height have typically utilised cross-sectional data. An alternative but less common approach is to use pre-to-post training change data, where the relationship between an improvement in jump height and a change in a factor is examined more directly. Our study compared the findings of these approaches. Such an evaluation is necessary because cross-sectional studies are currently a primary source of information for coaches when examining what factors to train to enhance performance. The countermovement jump of forty four males was analysed before and after an eight week training intervention. Correlations with jump height were calculated using both cross-sectional (pre-training data only) and pre-to-post training change data. Eight factors identified in the cross-sectional analysis were not significantly correlated with a change in jump height in the pre-to-post analysis. Additionally, only six of eleven factors identified in the pre-to-post analysis were identified in the cross-sectional analysis. These findings imply that: (a) not all factors identified in a cross-sectional analysis may be critical to jump height improvement, and (b) cross-sectional analyses alone may not provide an insight into all of the potential factors to train to enhance jump height. Coaches must be aware of these limitations when examining cross-sectional studies to identify factors to train to enhance jump ability. Additional findings highlight that while exercises prescribed to improve jump height should aim to enhance concentric power production at all joints, a particular emphasis on enhancing hip joint peak power may be warranted

CAN BIOMECHANICAL DIAGNOSTIC PROFILING IDENTIFY THE EFFECTIVENESS OF SPECIFIC TRAINING EXERCISES?

This study investigated the use of a diagnostic and prescriptive pathway that aims to determine the effectiveness of specific training exercises. The model was tested by examining if the effects of drop jump (DJ) training on countermovement jump (CMJ) performance could be explained by the degree to which performance determining factors (PDFs) for the CMJ were overloaded. Participants trained with DJ for 8 weeks yet no change in CMJ performance occurred. Of the 4 CMJ PDFs identified only hip rate of power development was overloaded by the DJ and none were enhanced with training. The results imply that the pathway was effective in identifying whether DJ training would enhance participants CMJ performance. The model could be used to determine if a given exercise would enhance a specific group of athletes prior to initiating training

Viscoelastic impact characterisation of solid sports balls used in the Irish sport of Hurling

In recent years, variability in behaviour of the sliotar, a small leather-bound ball used in the Irish sport of hurling, has become evident in championship matches. The inconsistency in performance was attributed to the range of constructions and material compositions of currently approved ball types. With a view to adopting a standard core, a new methodology has been commissioned to assess the dynamic impact behaviour of approved sliotar cores. In this paper, the relationship between the dynamic stiffness and the coefficient of restitution is presented with regard to material properties, ball construction and viscoelastic strain and strain-rate dependencies. The modern polymer ball types were shown to exhibit strain-rate sensitivity, while the performance of the traditional multi-compositional ball types exhibited lesser strain-rate dependence. The traditional balls types were shown to be up to 2.5 times stiffer than the modern ball types, with this finding having implications for ball energy dissipation

Balance as a predictor towards independent cycling

Cycling is a milestone for children. Learning to ride a bike is an acquired skill, often obtained with difficulty. Fundamental movement skills (FMS) are generally developed in early childhood. Children have the developmental potential to progress to the mature stage of most FMS by the age of 6, at which point they are able to combine FMS to produce specialised skills in sports and recreational activities like cycling. Balance, a subset of FMS, has often thought to be essential in cycling; however, there is no empirical evidence to support this statement. Thus, this study investigates if balance is a contributing factor to learning to cycle. 72 children (3.7+/-0.5) were assessed pre and post a 5 week intervention. The children were assessed on ability to cycle independently and balance ability. Ability to cycle independently was measured using a traditional bike. If the child was able to cycle without assistance (tester holding onto bike) they were given a score of 1 and if they could not a score of 0. No children were able to cycle independently at pre-intervention. Balance ability was measured using the balance subset of the Movement Assessment Battery for Children, second edition (MABC-2). All children attended 10 cycling lessons over 5 weeks. Linear regressions were run to assess whether the balance at pre-intervention predicted if a child would be able the cycle independently post-intervention. Balance ability did not predict cycling independently (r^2=.002, p>.05). The current results would suggest that the FMS skill of balance is not a contributing factor to learning to cycle. This result, while in contrast to the general assumption, is not surprising as most children do not reach the mastery level of FMS till the age of 6. Therefore, between 3 and 5 years, when children generally learn to cycle, they are not yet at the phase of refining FMS to produce sport specific skills. Further research should investigate (i) if other FMS subsets or a combination of FMS contribute to learning to cycle and (ii) if cycling is an independent skill learnt at parallel to FMS

Analysis of the joint kinematics of the 5 iron golf swing

The purpose of this study was to identify the performance determining factors of the 5-iron golf swing. Joint kinematics were obtained from thirty male golfers using a twelve camera motion analysis system. Participants were divided into two groups, based on their ball launch speed (high vs. low). Those in the high ball speed group were deemed to be the more skillful group. Statistical analysis was used to identify the variables which differed significantly between the two groups, and could therefore be classified as the performance determining factors. The following factors were important to performance success: (i) the ability of the golfer to maintain a large X Factor angle and generate large X Factor angular velocity throughout the downswing, (ii) maintain the left arm as straight as possible throughout the swing, (iii) utilise greater movement of the hips in the direction of the target and a greater extension of the right hip during the downswing and (iv) greater flexion of both shoulders and less left shoulder internal rotation during the backswing

Analysis of characterizing phases on waveforms – an application to vertical jumps

The aim of this study is to propose a novel data analysis approach, ‘Analysis of Characterizing Phases’ (ACP), that detects and examines phases of variance within a sample of curves utilizing the time, magnitude and magnitude-time domain; and to compare the findings of ACP to discrete point analysis in identifying performance related factors in vertical jumps. Twenty five vertical jumps were analyzed. Discrete point analysis identified the initial-to-maximum rate of force development (p = .006) and the time from initial-to-maximum force (p = .047) as performance related factors. However, due to inter-subject variability in the shape of the force curves (i.e non-, uni- and bi-modal nature), these variables were judged to be functionally erroneous. In contrast, ACP identified the ability to: apply forces for longer (p < .038), generate higher forces (p < .027) and produce a greater rate of force development (p < .003) as performance related factors. Analysis of Characterizing Phases showed advantages over discrete point analysis in identifying performance related factors because it: (i) analyses only related phases, (ii) analyses the whole data set, (iii) can identify performance related factors that occur solely as a phase, (iv) identifies the specific phase over which differences occur, and (v) analyses the time, magnitude and combined magnitude-time domains