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The interaction between the physical and mental loads associated with actual and simulated rugby league performanceThe aim of the current thesis was to develop knowledge of the ‘loads’ associated with rugby league match-play, with a particular focus on the effects of altered mental loads before and during exercise indicative of a rugby league match. Chapter 3 examined the test-retest reliability of movement, physiological and perceptual measures during and after a novel rugby match simulation, where movement commands were more random than those typical of match simulations. The most reliable measure of external load during bouts of the simulation was relative distance (typical error [TE] and coefficient of variation [CV%] = 1.5-1.6 m.min-1 and 1.4-1.5%, respectively), with all other movement characteristics possessing a CV% <5%. The most reliable measure of internal load, neuromuscular function and perceptual measures were for %HRmax during bout 1 (TE and CV% = 1.4-1.7% and 1-4-2.1%, respectively), MVC before (TE and CV% = 10.8-14.8 N·m and 3.8-4.6%, respectively), and average RPE (TE and CV% = 0.5-0.8 AU and 3.6-5.5%, respectively). The conclusion of this chapter was that randomisation of the movements during simulated activity to better reflect intermittent team sports has no detrimental effect on its reliability. Studies can therefore confidently examine alterations in several perceptual, neuromuscular, physiological and movement load measures related to rugby activity using stochastic movements. Chapter 4 examined the responses to a simulated rugby league protocol that was designed to include more random commands, and therefore require greater vigilance, than traditional team sport simulation protocols. The randomised simulation (RDM) was matched for the number and types of activity performed every 5.45 min in a control trial (CON), but included no repeated cycles of activity. The RDM trial was more mentally demanding than CON (Effect size (ES) = 0.56; ±0.57). Self-paced mean sprint performance increased in RDM (22.5 ± 1.4 vs. 21.6 ± 1.6 km∙h-1; ES = 0.50; ±0.45), which was accompanied by a higher RPE (14.3 ± 1.0 vs. 13.0 ± 1.4; ES = 0.87; ±0.54) and a greater number of errors in the Stroop Test (10.3 ± 2.5 vs. 9.3 ± 1.4 errors; ES = 0.65; ±0.67). MVC peak torque (CON = -48.4 ± 31.6 N.m, RDM = -39.6 ± 36.6 N.m) and voluntary activation (CON = -8.3 ± 4.8%, RDM = -6.0 ± 4.1%) was similarly reduced in both trials. Providing more random commands, requiring greater vigilance, can therefore alter performance and associated physiological, perceptual and cognitive responses to team sport simulations. Chapter 5 describes the subjective task load of elite rugby league match play using the NASA-TLX and examines their association with several contextual match factors, technical ii performance and external movement demands. Linear mixed modelling revealed that various combinations of contextual factors, technical performance and movement demands were associated with subjective task load (NASA-TLX). Greater number of tackles (η2 = 0.18), errors (η2 = 0.15) decelerations (η2 = 0.12), increased sprint distance (η2 = 0.13), losing matches (η2 = 0.36) and increased perception of effort (η2 = 0.27) lead to most likely – very likely increases in subjective total workload. These data provide a greater understanding of the internal load and their association with several contextual factors, technical performance and external movement demands during rugby league competition. The purpose of the final empirical chapter (Chapter 6) was to describe the effects of mental fatigue on simulated rugby league performance and to determine the effects of caffeine supplementation on simulated rugby league performance in the presence of mental fatigue. Completing a mentally demanding task increases participants’ subjective rating of mental fatigue (pre = 29 ± 25 AU; post = 55 ± 20 AU) immediately before completing a simulation protocol. Impairments in sprint speed (ES = -0.18; ±0.19), sprint to contact speed (ES = -0.20; ±0.27), high-intensity running (ES = -0.30; ±0.24), high metabolic power > 20 W·kg-1 (ES =-0.50; ±0.51) and time to complete a passing accuracy task (ES = 0.54; ±0.63) were observed after mental fatigue. Caffeine supplementation (5 mg.kg-1) attenuated several adverse effects of mental fatigue before exercise replicating the demands of rugby league match play, with increased sprint speed (ES = 0.40; ±0.18), high-intensity running (ES = 0.50; ±0.53), high metabolic power > 20 W·kg-1 (ES = 0.33; ±0.38) and decreased time to complete a passing accuracy test (ES =-0.70; ±0.45). Mental fatigue affected internal loads, external loads and skill performance during simulated rugby league match play that appear to be centrally regulated by a decreased motivation and increased perception of effort. However, a single dose of caffeine taken 60 min before performance can attenuate several of these negative effects. In summary, the current thesis highlights several interactions between the physical and mental loads associated with actual and simulated rugby league performance.
A Three-Season Analysis of Positional Demands in Elite English Rugby UnionThis thesis presents novel findings relating to the position-specific locomotive and performance-related characteristics of elite (club) level rugby union players in England using data gathered via global positioning systems and time-motion analysis over three seasons (2010 – 2013). In terms of sample size, this investigation represents one of the largest conducted and therefore provides information that is more representative than any published thus far. Moreover, the findings reported in the first study (of this thesis) directly challenge the practice adopted previously by researchers in this field of not considering the running capabilities of individual players when calculating their locomotive activities. The consequence of this is that for certain measures (involving speed zones), the values reported herein are a more appropriate reflection of elite players’ movement patterns than has been previously reported. For example, it emerged that had previous approaches been used, the average distances covered by players in a match would have been either under- or over-estimated by up to ~ 80% in high intensity running (HIR), and 86% in sprinting. In adopting subsequently the use of speed categories defined in relative terms, position-related differences were observed in locomotion. Namely, as a group, the backs covered the greatest distances, with the scrum half position covering the most (6,542 m) and the tighthead prop the least (4,326 m). The outside backs were found to “sprint” the most, albeit up to ten times less than previously reported. Similarly, position-specific performance behaviours were identified, with the forwards participating in ~ 40% more static exertions than the backs, the second row involved in the most rucks (~ 34% of team total) and the back row the most tackles (12 per match). Among the backs, different demands prevailed; the scrum half executed most passes (over 50% of team total), whereas the inside backs engaged in most tackles (8 per match) and the outside backs carried the ball the most (7 times per match). When broken down into 5-minute periods of play, notable changes in demands were evident. For instance, reductions in total distances (~ 7%), and distances at HIR (~ 16%) occurred in 5 the second half compared to the first, implying that the onset of fatigue and/or the employment of pacing strategies. Moreover, reductions in HIR following the most intense periods of play were seen (when compared to the average) for the inside (~ 23%) and outside backs (~ 20%), as was the number of static exertions for the front row (~ 21%), back row (~ 24%) and outside backs (~ 45%), suggesting the occurrence of ‘transient fatigue’ during a match. Collectively the current research provides a comprehensive overview of key physical demands of English Premiership rugby union. Not only does it provide ‘typical’ position-related data, but also provides some insight into the most intense scenarios for elements of locomotive movement and static exertions, which together could assist practitioners/coaches in devising individualised training programmes to prepare players optimally for competition.
The Unsuitability of Energy Expenditure Derived From Microtechnology for Assessing Internal Load in Collision-Based ActivitiesThis aim of this study was to examine the validity of energy expenditure derived from micro-technology when measured during a repeated effort rugby protocol. Sixteen male rugby players completed a repeated effort protocol comprising 3 sets of 6 collisions during which movement activity and energy expenditure (EEGPS) were measured using micro-technology. In addition, energy expenditure was also estimated from open circuit spirometry (EEVO2). Whilst related (r = 0.63, 90%CI 0.08-0.89), there was a systematic underestimation of energy expenditure during the protocol (-5.94 ± 0.67 kcalmin-1) for EEGPS (7.2 ± 1.0 kcalmin-1) compared to EEVO2 (13.2 ± 2.3 kcalmin-1). High-speed running distance (r = 0.50, 95%CI -0.66-0.84) was related to EEVO2, while Player Load was not (r = 0.37, 95%CI -0.81-0.68). Whilst metabolic power might provide a different measure of external load than other typically used micro-technology metrics (e.g. high-speed running, Player Load), it underestimates energy expenditure during intermittent team sports that involve collisions.