Beaven, MartynIrwin, Emma2026-10-052026-10-052026https://hdl.handle.net/10289/18686Short-wavelength (blue) light has consistently been shown to enhance alertness and cognitive performance by stimulating intrinsically photosensitive retinal ganglion cells that activate arousal-related brain regions. Despite this mechanistic basis, its application as a pre-performance tool in open-skill team sport remains largely underexamined. Field hockey, which places substantial perceptual-cognitive demands on athletes, requiring rapid decision-making, reactive agility, and perceptual-motor integration under time pressure and physical fatigue, therefore, represents a theoretically appropriate context in which to examine whether these effects translate to applied sports performance. Chapter One critically reviews the existing literature on the performance demands of field hockey, the physiological and neurological mechanisms underpinning short-wavelength light exposure, and its established effects on alertness, cognitive performance and physical readiness. The review identifies a clear gap in sport-specific evidence, noting that while laboratory-based research consistently supports blue light as an acute cognitive enhancer, its translation to ecologically valid athletic environments, particularly open-skill team sports requiring rapid perceptual cognitive processing, remains largely underexplored. Chapter Two presents a randomised crossover study investigating the acute effects of blue light exposure on reaction time, reactive agility and change-of-direction performance in eleven competitive field hockey players. Participants were exposed to either short-wavelength blue light (~480nm, 6500K) or a placebo condition for 15 minutes before testing, with performance assessed using a reaction time protocol across four time points, a reactive Y-agility test, and a 505 change-of-direction test, each completed with and without a hockey stick and ball. A small-sided game provided an ecologically valid fatigue stimulus. Blue light had no meaningful effect on change-of-direction performance, consistent with its proposed mechanism of action on cognitively loaded tasks rather than tasks reliant on neuromuscular capacity. Reactive agility improved significantly within the blue light condition in the without-stick conditions (3.04s to 2.89s, p = .027), and reaction time decreased progressively under blue light from baseline through to halftime, associated with a large within-condition effect (d = 0.91) and a moderate between-condition difference at halftime (d = 0.60). A near-significant elevation in pre-small-sided game heart rate was also observed under blue light relative to placebo (128 vs. 117 bpm, p =.051). Chapter Three synthesises these findings within the broader literature, arguing that the convergent pattern across reaction time, reactive agility, and pre-exercise heart rate reflects a coherent picture of cortical arousal difficult to attribute to placebo response alone. Key limitations include sample size, absence of neurophysiological measures, and risks of poorly timed evening use of light on melatonin suppression and sleep. Future research should prioritise adequately powered and sex-stratified replication, dose-response investigations, and neurophysiological outcome measures to directly assess the cortical arousal mechanism. Taken together, this thesis provides preliminary but directionally consistent evidence that blue light exposure can enhance cognitively demanding aspects of field hockey performance, extending a body of evidence largely confined to laboratory settings into a more ecologically valid, sport-specific context and supporting its potential as a simple, accessible pre-performance tool in open-skill team sport.enAll items in Research Commons are provided for private study and research purposes and are protected by copyright with all rights reserved unless otherwise indicated.blue lightdecision-makingagilityfield hockeyreaction timeThesis