Soccer : physical characteristics, physical demands of match-play and effective physical conditioning

The overall purpose of this thesis was to examine the physical aspects of high performance soccer. As such, four interrelated studies were designed to pursue this purpose. Each study was designed to overcome certain distinct methodological limitations of previous science and football (soccer) research and build upon existing research. The research designs for each of the four studies were methodologically different and progressed from previous research design incorporating data collected and analysed from text and internet sources, computerised video-analysis of interactive televised material and combined performance and laboratory assessments. In the following section the purpose of each study included in this thesis is provided and the rationale underpinning the selection of each research design is explained. Study 1: Analysis of Age, Stature, Body Mass, BNH and Quality of Elite Soccer Players from four European Leagues For many sports, there are specific physical characteristics that indicate suitability for, or potential to compete in that sport at the highest level. Various anthropometric characteristics of athletes have been shown to be reasonable predictors for participation at the highest level in sports such as swimming (Ackland et al., 1993), basketball, rugby league and American football (Norton and Olds, 2000). Surprisingly, there is no research available exploring these characteristics in soccer, particularly within the elite European soccer. It might well be that the recent changes in demands in soccer( Williams et al., 1999) PhD Thesis 6 Jonathan R- Bloomfield have been accompanied by physical characteristic changes in soccer players that have been of greater magnitude than that of the normal population. This is an important issue because even small changes in these physical characteristics of players could result in a large reduction in the pool of people to draw from in the general population who have the suitable physical characteristics to be successful in soccer (Olds, 2001). Furthermore, the comparison of players in different leagues and in different positions might provide some valuable information regarding the different demands placed on soccer players in different leagues (Reilly et al, 2000a; Rienzi et al, 2000; Strudwick et al., 2002). It is well documented that different positions in soccer constitute various different demands. Such findings suggest heterogeneity in physical characteristics that might be important for success in particular positions in soccer (Strudwick et al., 2002). The first aim of the present study was to investigate whether there are physical differences (age, stature, body mass, body mass index) between players in different positions in four European soccer leagues. This will also provide information into the diversity in playing style as well as the variation in what is being valued in soccer players in the various countries. This results in valuable information for the adaptation of different physical conditioning regimes as well as implications for talent identification (Fisher and Dean, 1998). The second aim of the present study was to assess the quality of the players of each of the four European leagues by surveying their international status, nationality and FIFA world ranking as well as participation in the FIFA World Cup 2002. This will offer information regarding the actual quality of international players within these leagues which, in turn, provides information about which league would be of the highest quality, differences in playing style and player selection. As the four leading European leagues were selected for analysis, the results provide beneficial information concerning the current status and possible future development of European soccer. Study 2: The 'Bloomfield Movement Classification': Motion Analysis of Individual Soccer Players In close relation with the investigation of the physical characteristics of elite level players, it was also aimed to identify the physical demands of performance. Computerised video-analysis was selected as the most appropriate platform to incorporate a study using the time-motion analysis methodology. This involves the notation of various subjectively or objectively chosen modes of motion which are digitally timed throughout the performance. To date, fewer than 8 modes of motion have often been chosen in time-motion investigation in soccer which arguably does not provide a sufficient degree of specificity to detail the physical demands. A high element of performance specificity must be established to elicit a high degree of transfer from competition into a training regime to optimise competitive performance (Henry, 1968; Barnett et al., 1973; Sale and MacDougall, 1981; Rosenbaum, 1987; Morrissey et al., 1995; Hill et al., 1998). The present study outlined a new approach to time-motion analysis through a method involving a greater depth of detail concerning modes of timed-motion, as well as other non-timed movements, directions, intensities, turning and 'On the Ball' categories. The aim of this study was to present a new methodology and establish reliability. The purpose was to provide a new method to perform a more detailed time-motion analysis study in soccer performance to be used in the third study of this thesis. PhD Thesis 8 Jonathan R. Bloomfield Study 3: Physical Demands of Outfield Positions in FA Premier League Soccer. To elicit an enhancement in soccer performance, it is considered important to analyse the physical demands of match-play (Reilly and Thomas, 1976; All and Farrally, 1991a; Hughes, 2003). Time-motion analysis has been used to investigate these demands. However, many limitations exist with previous research, one of which being the range of classifications used in the collection of data- A high degree of performance specificity is desired to improve coaching practices such as physical conditioning (Barnett et al., 1973). To this end, a new time-motion analysis methodology was designed (see Study 2) and aimed at providing a new level of specificity of performance into the physical demands of high level soccer. Also, the majority of soccer-related time-motion analyses have reported macroscopically with total frequency, total duration or total distance covered providing a summary of the overall physical requirements of soccer. As soccer match-play is essentially an intermittent exercise (Bangsbo, 1994e), it is important to progress the knowledge of the physical nature of the sport and further provide a higher level of specific detail. The aims of the present study were to provide detail regarding intermittent patterns of Purposeful Movement (PM) and Recovery (R), performed by players of three different positions (defender, midfielder and striker), to investigate the reoccurrence of bouts of PM and R within selected time phases and finally provide time-motion analysis of the PM using the BMC. PhD Study 4: Effective Conditioning for Soccer Match-Play The interaction of multiple dynamic physical activities often produces a hybrid of physiological and biomechanical stresses. Higher levels of soccer require increased levels of physical fitness through increased demands from high intensity activity (O'Donoghue et al., 2001; Strudwick and Reffly, 2001; Mohr et al., 2003). Therefore, increased ability to perform complex chains of movement skills (agility) in conjuncture with speed (both acceleration and deceleration) and quickness (overcoming inertia) are relative to high level performance (Withers et al., 1982; Bangsbo, 1992; Reilly, 1994a). This occurs through processes of motor learning and physical conditioning with the rules of specificity and overload as key underlying principles. In order to facilitate motor learning, practice should contain variability within each session in preference to the repeated rehearsal of a single skill (Fitts, 1964; Henry, 1968; Barnett et al., 1973; Carlson and Yaure, 1990; Vereijken, 1991; Whiting and Vereijken, 1993; Bangsbo, and Peitersen, 2000; WiHiams, 2002). This may take the form of programmed and controlled (e. g. SAQ0 conditioning) or random and semi-controlled (e. g. small-sided games) practice methods. Hoff et al., (2002) identified that both methods are credible for soccer conditioning. The main aim of this study was to investigate the efficacy of programmed and random motor learning and physical conditioning methods and investigate neurophysiological. and performance adaptations, A second aim was to investigate the necessity of the use of specialised SAQ8 equipment for the purposes of programmed conditioning

The effect of an early dismissal on player work-rate in a professional soccer match

The aim of this study was to examine the effects of an early dismissal (after 5-minutes play) on work-rate in a professional soccer match. A computerised player tracking system was used to assess the work-rates of seven players who completed the match on the team with 10 players. A minute-by-minute analysis of the remaining 91mins following the dismissal was performed for the total distance covered, the distance covered in five categories of movement intensity and the recovery time between high-intensity efforts for each player. The data were calculated for each half and for three equal intervals within each half and profiled against normative data for the same players obtained from analyses of 15 games in the same season. Following the dismissal, the players covered a greater total distance than normal (p<0.025), particularly in moderate-intensity activities (p<0.01) and had shorter recovery times between high-intensity efforts (p<0.025). In contrast, there was a significant reduction between game halves for total distance covered at both the highest (p<0.025) and lowest running intensities (p<0.01). However, there were no differences in high-intensity activities across the three intervals in the second-half. These findings suggest that in 11 v 11, players may not always utilise their full physical potential as this match illustrated an increase in overall work-rate when reduced to 10 players. However, as a team with 10 players is likely to incur higher levels of fatigue, tactical alterations may be necessary and/or players may adopt a pacing strategy to endure the remainder of the match

Evidence for changes in historic and future groundwater levels in the UK

We examine the evidence for climate-change impacts on groundwater levels provided by studies of the historical observational record, and future climate-change impact modelling. To date no evidence has been found for systematic changes in groundwater drought frequency or intensity in the UK, but some evidence of multi-annual to decadal coherence of groundwater levels and large-scale climate indices has been found, which should be considered when trying to identify any trends. We analyse trends in long groundwater level time-series monitored in seven observation boreholes in the Chalk aquifer, and identify statistically significant declines at four of these sites, but do not attempt to attribute these to a change in a stimulus. The evidence for the impacts of future climate change on UK groundwater recharge and levels is limited. The number of studies that have been undertaken is small and different approaches have been adopted to quantify impacts. Furthermore, these studies have generally focused on relatively small regions and reported local findings. Consequently, it has been difficult to compare them between locations. We undertake some additional analysis of the probabilistic outputs of the one recent impact study that has produced coherent multi-site projections of changes in groundwater levels. These results suggest reductions in annual and average summer levels, and increases in average winter levels, by the 2050s under a high greenhouse gas emissions scenario, at most of the sites modelled, when expressed by the median of the ensemble of simulations. It is concluded, however, that local hydrogeological conditions can be an important control on the simulated response to a future climate projection

The role of motion analysis in elite soccer

The optimal physical preparation of elite soccer (association football) players has become an indispensable part of the professional game especially due to the increased physical demands of match-play. The monitoring of players’ work-rate profiles during competition is now feasible through computer-aided motion analysis. Traditional methods of motion analysis were extremely labour intensive and were largely restricted to university- based research projects. Recent technological developments have meant that sophisticated systems, capable of quickly recording and processing the data of all players’ physical contributions throughout an entire match, are now being used in elite club environments. In recognition of the important role motion analysis now plays as a tool for measuring the physical performance of soccer players, this review critically appraises various motion analysis methods currently employed in elite soccer and explores research conducted using these methods. This review therefore aims to increase the awareness of both practitioners and researchers of the various motion analysis systems available, identify practical implications of the established body of knowledge, while highlighting areas that require further exploration

Do sleep difficulties exacerbate deficits in sustained attention following traumatic brain injury?

Sustained attention has been shown to be vulnerable following traumatic brain injury (TBI). Sleep restriction and disturbances have been shown to negatively affect sustained attention. Sleep disorders are common but under-diagnosed after TBI. Thus, it seems possible that sleep disturbances may exacerbate neuropsychological deficits for a proportion of individuals who have sustained a TBI. The aim of this prospective study was to examine whether poor sleepers post-TBI had poorer sustained and general attentional functioning than good sleepers post-TBI. Retrospective subjective, prospective subjective, and objective measures were used to assess participants’ sleep. The results showed that the poor sleep group had significantly poorer sustained attention ability than the good sleep group. The differences on other measures of attention were not significant. This study supports the use of measures that capture specific components of attention rather than global measures of attention, and highlights the importance of assessing and treating sleep problems in brain injury rehabilitation

Quantifying uncertainty in predictions of groundwater levels using formal likelihood methods

Informal and formal likelihood methods can be used to quantify uncertainty in modelled predictions of groundwater levels (GWLs). Informal methods use a relatively subjective criterion to identify sets of plausible or behavioural parameters of the GWL models. In contrast, formal methods specify a statistical model for the residuals or errors of the GWL model. The formal uncertainty estimates are only reliable when the assumptions of the statistical model are appropriate. We apply the formal approach to historical reconstructions of GWL hydrographs from four UK boreholes. We test whether a model which assumes Gaussian and independent errors is sufficient to represent the residuals or whether a model which includes temporal autocorrelation and a general non-Gaussian distribution is required. Groundwater level hydrographs are often observed at irregular time intervals so we use geostatistical methods to quantify the temporal autocorrelation rather than more standard time series methods such as autoregressive models. According to the Akaike Information Criterion, the more general statistical model better represents the residuals of the GWL model. However, no substantial difference between the accuracy of the GWL predictions and the estimates of their uncertainty is observed when the two statistical models are compared. When the general model is applied, significant temporal correlation over periods ranging from 3 to 20 months is evident for the different boreholes. When the GWL model parameters are sampled using a Markov Chain Monte Carlo approach the distributions based on the general statistical model differ from those of the Gaussian model, particularly for the boreholes with the most autocorrelation. These results suggest that the independent Gaussian model of residuals is sufficient to estimate the uncertainty of a GWL prediction on a single date. However, if realistically autocorrelated simulations of GWL hydrographs for multiple dates are required or if the distributions of the GWL model parameters are of interest, then the more general statistical model should be used

Strengthening Referral Networks for Management of Hypertension Across the Health System (STRENGTHS) in western Kenya: a study protocol of a cluster randomized trial

BACKGROUND: Hypertension is a major risk factor for cardiovascular disease (CVD), yet treatment and control rates for hypertension are very low in low- and middle-income countries (LMICs). Lack of effective referral networks between different levels of the health system is one factor that threatens the ability to achieve adequate blood pressure control and prevent CVD-related morbidity. Health information technology and peer support are two strategies that have improved care coordination and clinical outcomes for other disease entities in other settings; however, their effectiveness and cost-effectiveness in strengthening referral networks to improve blood pressure control and reduce CVD risk in low-resource settings are unknown. METHODS/DESIGN: We will use the PRECEDE-PROCEED framework to conduct transdisciplinary implementation research, focused on strengthening referral networks for hypertension in western Kenya. We will conduct a baseline needs and contextual assessment using a mixed-methods approach, in order to inform a participatory, community-based design process to fully develop a contextually and culturally appropriate intervention model that combines health information technology and peer support. Subsequently, we will conduct a two-arm cluster randomized trial comparing 1) usual care for referrals vs 2) referral networks strengthened with our intervention. The primary outcome will be one-year change in systolic blood pressure. The key secondary clinical outcome will be CVD risk reduction, and the key secondary implementation outcomes will include referral process metrics such as referral appropriateness and completion rates. We will conduct a mediation analysis to evaluate the influence of changes in referral network characteristics on intervention outcomes, a moderation analysis to evaluate the influence of baseline referral network characteristics on the effectiveness of the intervention, as well as a process evaluation using the Saunders framework. Finally, we will analyze the incremental cost-effectiveness of the intervention relative to usual care, in terms of costs per unit decrease in systolic blood pressure, per percentage change in CVD risk score, and per disability-adjusted life year saved. DISCUSSION: This study will provide evidence for the implementation of innovative strategies for strengthening referral networks to improve hypertension control in LMICs. If effective, it has the potential to be a scalable model for health systems strengthening in other low-resource settings worldwide