The 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
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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
