A Comparison of Video and Accelerometer Based Approaches Applied to Performance Monitoring in Swimming.

The aim of this paper is to present a comparison of video- and sensor based studies of swimming performance. The video-based approach is reviewed and contrasted to the newer sensor-based technology, specifically accelerometers based upon Micro-Electro-Mechanical Systems (MEMS) technology. Results from previously published swim performance studies using both the video and sensor technologies are summarised and evaluated against the conventional theory that upper arm movements are of primary interest when quantifying free-style technique. The authors conclude that multiple sensor-based measurements of swimmers’ acceleration profiles have the potential to offer significant advances in coaching technique over the traditional video based approach

Mass mortalities in bivalve populations: A review of the edible cockle Cerastoderma edule (L.)

Mass mortalities in bivalve populations have long been of particular concern, especially when the species supports a commercial fishery or is of conservation interest. Here we consider the evidence of mass mortalities of the edible cockle, Cerastoderma edule (L.). Through the construction of a conceptual model eight potential factors (or groups of factors) which may cause mass mortalities are identified and reviewed. These include: food limitation; density; oxygen depletion and organic loadings; temperature and salinity; parasites, pathogens and commensals; toxicants and other persistent pollutants; predation, and changes in sediment, suspended solids, topography and bathymetry. The interplay between factors in recognized and discussed based on evidence mainly from the published literature relating to temperate edible cockle beds. Anecdotal evidence is also reported from a structured survey of site-specific evidence provided by fisheries managers in England and Wales. Case studies from the UK and Europe indicate that there is often no single, clear generic cause of mass mortalities in cockle populations. The importance of linked site-specific scientific investigations and laboratory-based experiments to fill the gaps in our current understanding of mass mortalities in bivalve species is highlighted as necessary to take account of both local extrinsic and intrinsic factors

Inter-Rater Reliability and Criterion Validity of Scatter Diagrams as an Input Method for Marksmanship Analysis: Computerised Notational Analysis for Archery

Basic notational systems exist in many sports but may not always be formally named as such. This paper outlines the validity and reliability of using a computerised scatter diagram as an input method for the analysis of marksmanship in target sports with Archery used as an example sport. Software was created to represent a standard FITA 122cm target face. An Archer shot 72 arrows, these were measured to create coordinates of each arrow. Twelve images (6 arrows per image) were shown to 10 operators. Operators input each arrow position into the software to produce a coordinate for each arrow. The coordinates where additionally processed using marksmanship statistics, Accuracy Constant Error (ACE), Accuracy Variable Error (AVE) and Precision (Mean Radius-MR). ICC was used to test validity and PPMC to test inter-rater reliability of the raw data and error analysis on the processed data. Raw results showed strong positive correlations for validity against the measured coordinates (>.977) and high levels of inter-rater reliability(>.969). Processed results show less than 2% error to that of measured results. Systems such as this allow coach/athlete/researcher to track varying equipment setups, changes to biomechanics, physiology and psychology, allowing for continued development of athlete, sport and equipment

Technical factors utilised by elite archers: towards setting an agenda for archery

Archery, in one form or another, has been around for thousands of years yet research into what makes an archer 'good' is still in its infancy. There are several variations over bow type and different competitions which can be competed, previous works have focused on Recurve (Olympic) bow types whilst Compound have generally been ignored. Research in the area has tended to focus on muscle activation patterns using Electromyography (EMG) and aiming based studies, where generally scores are used as a factor to correlate to. AIM: The aim of this research is to offer a development from the use of score incorporating additional marksmanship based statistics. These are used to identify which factors are most critical to elite archers, allowing the identification of the technical performance indicators. METHOD: A Matlab script was produced to represent a target face where arrow locations can be input. The coordinates from these are used to calculate accuracy and precision, and additional tertiary factors. The system was tested utilising known arrow placements, tested by 10 individuals, demonstrating accurate results. The system was then used to analyse arrow placements of the top 4 archers in the finals matches from 2006-2011 Archery World Cup, World Championships and Olympics, both Recurve and Compounds in both genders analysed where possible. RESULTS: Results show that for Recurve there are statistically significant differences in accuracy and precision between 1st and 2nd places, however the compounds are closer matched under these measures. Interestingly, 3rd place archers generally performed better than the 2nd place archer in their final match. The results prompt new thinking towards an agenda for archery based research: • deeper understandings of the psychological differences between finishing places • analysis of bow setups using these methods • rule changes considering a further elimination round between silver and bronze • deeper analysis for previous work

Combined EEG and eye tracking in sports skills training and performance analysis

The use of mobile EEG brainwave monitoring and eye-tracking recorded synchronously during the training of sports skills offers significant opportunities but creates challenges. Opportunities: ♦ Measuring neurocognitive activity and visual focus in real time which can be used to provide immediate feedback to the coach, in ‘real world’ settings, for optimising training protocols for the individual athlete. ♦ Use of sound output (‘sonification’) in proportion to EEG regions of interest as a neurofeedback mechanism for athlete self-training. ♦ Application of visualisation protocols and ‘EEG-driven’ PC games where game feedback based on state of mind is used to optimise mental state prior to performance. ♦ Examining the relationship between eye movement and neuro activity (e.g. saccades and gamma waves) and in athlete coaching interventions such as sports visual scanning strategies, Eye Movement Desensitisation & Reprocessing (EMDR) therapy, focussed relaxation, etc. Challenges: ♦ The recording of EEG during gross motor behaviour is subject to non-brain artefacts in the raw (time-domain) EEG, due to the much larger (than EEG) electrical voltages arising from muscle and eye movements. Practical approaches and signal processing (frequency domain spectrum) techniques to address these problems will be discussed. ♦ The synchronisation of data recorded on different types of equipment (e.g. EEG, eyetracker, video, sound, EMG, etc.) with different ‘clocks’ and diverse data formats is difficult – both in terms of time-stamping the original recordings across all the systems and playing them back synchronously for subsequent performance analysis. Progress on creating real-time data export methods which allow synchronous data recording and playback will be reported. Examples of studies carried out in archery, golf, motorsport, football and skiing will be discussed, with a focus on archery where: ♦ Measurements were taken from intermediate, county level, near elite and elite archers. ♦ Archery was chosen to demonstrate the real-time and in-situ quantification of neural activity compared with target-based measures of performance that archery provides, over a range of time-spans and skills. ♦ Results demonstrate that there are significant and measurable changes in EEG patterns during a shot with evidence suggesting that the patterns vary as a function of skill level, but not simply as a function of score. Significance of each of these studies for goal-directed learning and performance enhancement are discussed

Quantification of performance analysis factors in front crawl swimming using micro electronics: a data rich system for swimming.

The aim of this study is to increase the depth of data available to swimming coaches in order to allow them to make more informed coaching decisions for their athletes in front crawl swimming. A coach’s job is to assist with various factors of an individual athlete to allow them to perform at an optimum level. The demands of the swimming coach require objective data on the swim performance in order to offer efficient solutions (Burkett and Mellifont, 2008). The main tools available to a coach are their observation and perceptions, however it is known that these used alone can often result in poor judgment. Technological progress has allowed video cameras to become an established technology for swim coaching and more recently when combined with software, for quantitative measurement of changes in technique. This has allowed assessment of swimming technique to be included in the more general discipline of sports performance analysis. Within swimming, coaches tend to observe from the pool edge, limiting vision of technique, but some employ underwater cameras to combat this limitation. Video cameras are a reliable and established technology for the measurement of kinematic parameters in sport, however, accelerometers are increasingly being employed due to their ease of use, performance, and comparatively low cost. Previous accelerometer based studies in swimming have tended to focus on easily observable factors such as stroke count, stroke rate and lap times. To create a coaching focused system, a solution to the problem of synchronising multiple accelerometers was developed using a maxima detection method. Results demonstrated the effectiveness of the method with 52 of 54 recorded data sets showing no time lag error and two tests showing an error of 0.04s. Inter-instrument and instrument-video correlations are all greater than r = .90 (p < .01), with inter-instrument precision (Root Mean Square Error; RMSE) ≈ .1ms−2, demonstrating the efficacy of the technique. To ensure the design was in line with coaches' expectations and with the ASA coaching guidelines, interviews were conducted with four ASA swim coaches. Results from this process identified the factors deemed important: lap time, velocity, stroke count, stroke rate, distance per stroke, body roll angle and the temporal aspects of the phases of the stroke. These factors generally agreed with the swimming literature but extended upon the general accelerometer system literature. Methods to measure these factors were then designed and recorded from swimmers. The data recorded from the multi-channel system was processed using software to extract and calculate temporal maxima and minima from the signal to calculate the factors deemed important to the coach. These factors were compared to video derived data to determine the validity and reliability of the system, all results were valid and reliable. From these validated factors additional factors were calculated, including, distance per stroke and index of coordination and the symmetry of these factors. The system was used to generate individual profiles for 12 front crawl swimmers. The system produced eight full profiles with no issues. Four profiles required individualisation in the processing algorithm for the phases of the stroke. This was found to be due to the way in which these particular swimmers varied in the way they fatigued. The outputs from previous systems have tended to be either too complicated for a coach to understand and interpret e.g. raw data (Ohgi et al. 2000), or quite basic in terms of output e.g. stroke rate and counts (Le Sage et al. 2011). This study has added to the current literature by developing a system capable of calculating and displaying a breadth of factors to a coach. The creation of this system has also created a biomechanical research tool for swimming, but the process and principles can be applied to other sports. The use of accelerometers was also shown to be particularly useful at recording temporal activities within sports activities. Using PC based processing allows for quick turnaround times in the processing of detailed results of performance. There has been substantial development of scientific knowledge in swimming, however, the exchange of knowledge between sport science and coaches still requires development (Reade et al. 2008; Williams and Kendall 2007). This system has started to help bridge the gap between science and coaching, however there is still substantial work needed. This includes a better understanding of the types of data needed, how these can be displayed and level of detail required by the coach to allow them to enact meaningful coaching programmes for their athletes

Data mining of portable EEG brain wave signals for sports performance analysis: An Archery case study

BACKGROUND ♦ Achievement in high performance sport requires an appropriate ‘state of mind’, which is trained alongside the physical skills. ♦ However, quantification of mental state during coaching is often difficult. ♦ With the advent of a new generation of portable compact EEGs and wireless eye tracking devices, one can measure the neurocognitive activity of an athlete’s brain and their visual focus simultaneously in ecologically representative training scenarios. AIM/OBJECTIVES ♦ We present evidence suggesting that the ‘state of mind’ of an athlete can be measured and compared with target-based performance measures. METHOD ♦ Measurements were taken from intermediate, county level, near elite and elite archers investigating: o quantification of EEG brain wave signals comparing archers of different abilities o correlation of EEG data across shots as a function of marksmanship o prototyping real-time EEG data feedback using sound during training o synchronous EEG and eye tracking ♦ Archery was chosen to demonstrate the real-time and in-situ quantification of neural activity compared with target-based measures of performance that archery provides, over a range of timespans and skills. ♦ Mental performance was explored during stages of a shot, across shots within a set, or across different sessions. RESULTS ♦ Results demonstrate that there are significant and measurable changes in EEG patterns during a shot with evidence suggesting that the patterns vary as a function of skill level, but not simply as a function of score. ♦ Significance of each of these outcomes for goal-directed learning and performance enhancement are discussed. DISCUSSION ♦ This may provide coaches and athletes with real-time EEG feedback to identify differing mental skill execution compared to a baseline or aspirational measurement from another athlete. ♦ Future work includes injury recovery/prevention and welfare, rehabilitation, and work with mobility-challenged non-athletes

In vivo through range passive stiffness of the lumbar spine: a meta-analysis of measurements and methods

Passive spinal stiffness is an important property thought to play a significant role in controlling spinal position and movement. Measuring through-range passive stiffness in vivo is challenging with several methods offered in the literature. Currently, no synthesis of values or methods exists to which to compare literature to. This study aims to provide a contemporary review and quantitative synthesis of the through-range in vivo passive lumbar spinal stiffness values for each of the cardinal planes of movement. A structured systematic search, following PRISMA guidelines, of 28 electronic databases was conducted in 2022. Articles were restricted to peer-reviewed English language studies investigating in vivo through-range passive stiffness of the lumbar spine. Thirteen studies were included, ten relating to flexion/extension, four to lateral bending and five to axial rotation. Average stiffness values, as weighted means and confidence intervals, for each of the four sections of the moment-movement curves were synthesised for all planes of movement. Lateral bending was found to be the comparatively stiffest movement followed by flexion and then axial rotation. Future research should focus on the validity and reliability of measurement techniques. Axial rotation would also benefit from further study of its latter stages of range

Technique utilisation and efficiency in competitive Brazilian Jiu-Jitsu matches at white and blue belts

Despite its increasing popularity, little is known about Brazilian Jiu- Jitsu and what makes a successful fighter. This work aims to start answering questions about the most used and successful techniques to allow development of coaching methods towards enhancing performance at lower belt levels. One-hundred and forty tournament fights were analysed. The most common takedown was guardpull with 94% success. Significantly more single leg takedowns were attempted for blue belts (BBs), compared to white belts (WBs) (p = 0.013). However, there was no significant difference in success (p = 0.150). WBs used three main guardpasses with 93% covering knee slice, knee pin and bullfighter. A greater variety of passes were witnessed at BB with 71% coming from these three passes. The four most commonly attempted guard sweeps were scissor sweep, back take, Xguard sweep and SitUp sweep all experiencing varying levels of success: 55% for the scissor sweep, 60% back take, 63% Xguard sweep and 38% for the sit up sweep. Of all the submissions attempted 34% were for arm bar, 21% triangle, 12% cross collar choke but there were almost an inverse relationship between use and success with the least used having higher success rates, demonstrating that variety in submissions could lead to greater chances of success