By developing strong, self-sustaining individuals in organisations, employees will need to withstand the forces of stressors and be able to cope with continuous changes within their working environment. To move the equilibrium level from the current to the desired condition, the field of forces must be altered - by adding driving forces and by removing restraining forces. An individual's sense of coherence may either alleviate or aggravate reactions to a stressor and moderate the impact of occupational stressors on the individual's affective outcomes. The objectives of this study were to validate the 13-item version of the Orientation to Life Questionnaire (OLQ) (Antonovsky, 1987) and to determine the experience of employees with high levels of sense of coherence regarding helping and restraining factors within the workplace (compared to that of those with a low sense of coherence). A cross-sectional s w e y design was used. The total population (N = 2 678) of employees in a financial institution in Gauteng was used in this study. Random samples of groups with a strong (n = 300) and low (n = 300) sense of coherence were taken for purposes of the qualitative study. The OLQ (Antonovsky, 1987) and a biographical questionnaire were administered. The scale showed acceptable reliability and construct validity. The study set out to determine the applicability of the theoretical model of sense of coherence to employees in a financial institution. Reliability analysis revealed that the three subscales of sense of coherence were sufficiently internally consistent. The reliability of the measuring instrument were assessed with the use of Cronbach alpha coefficients. Descriptive statistics (e.g. mean and standard deviations) were used to analyse the data. By using the structural equation modelling approach, a one-dimensional factor structure for sense of coherence amongst employees in a financial institution emerged. The reliability analysis revealed that the alpha scores were acceptable. It can therefore be concluded that the 13-item version of the OLQ is a reliable and valid measuring instrument. The results showed that although employee groups with high and low levels of sense of coherence are experiencing similar helping and restraining factors within their working environment, helping factors are being experienced with a higher frequency by groups with high levels of sense of coherence and restraining factors with a higher frequency by groups with low levels of sense of coherence. Recommendations were made for future research. / Thesis (M.A. (Industrial Psychology))--North-West University, Potchefstroom Campus, 2007

In this thesis the effects of individual and multiple environmental stressors (physical and chemical) are examined in inbred and outbred zebrafish (Danio rerio, Hamilton), a model species used in ecotoxicology and environmental risk assessment (ERA). The central question addressed is, are inbred laboratory animals representative and protective of wild populations? That is, are inbred fish equally or more sensitive to chemicals and other stressors compared with more outbred (wild) fish? A combination of tools and approaches incorporating traditional (eco)toxicology and population genetics have been employed, together with more contemporary molecular genetics and population modelling, to compare and contrast a range of responses in inbred and outbred zebrafish exposed to the endocrine disrupting chemical clotrimazole and/or temperature elevation in the laboratory. The choice of test species was based on our broad understanding of its basic biology, extending from the molecular level to the population level, and its wide use as a model organism in (eco)toxicology. Selection of the test chemical clotrimazole and temperature was based on a shared mode of action, aromatase inhibition, and therefore their ability to block oestrogen production, impair reproduction, promote male development and skew population sex ratios in zebrafish. A cascade of responses were compared in inbred and outbred zebrafish, including changes in the levels of expression of genes for gonadal aromatase and other steroidogenic enzymes, circulating sex steroid hormones, gonadal sex differentiation and development (via gonadal histopathology) and reproductive fitness (female fecundity, paternity and viability of embryos). Amongst the most striking results were directional skews in sex ratio towards males in response to clotrimazole (Chapter 5) and elevated temperature exposure (Chapter 7). Inbred fish were generally more responsive compared to outbreds, which showed evidence of physiological and developmental compensation, resulting in lower male-sex skews and superior fitness in terms of male reproductive success (paternity and viability of embryos). The greater effects observed in inbred fish were attributed to inbreeding×environment interactions and the amplification of inbreeding depression. Although no empirical genetic evidence of this mechanism is presented (loss of heterozygosity at quantitative trait loci and concomitant loss of heterosis and/or the expression of recessive, deleterious alleles in homozygotes), supporting evidence was provided by increased phenotypic variance in some apical endpoints in inbred fish, including specific growth rate and fecundity. This increased variance also has the potential to counteract the higher levels of response observed in inbreds, because the power to detect statistically significant changes in responses is reduced. This trade-off was demonstrated for specific growth rate. Crucially, significant male-sex ratio skews (>80%) were induced at substantially lower clotrimazole exposure concentrations (1.7 µg l-1) in combination with elevated temperature (33°C), compared with exposure concentrations (43.7 µg l-1) generating similar sex ratio skews at the standard test temperature of 28°C. These temperatures represent current and predicted 2100 (elevated) mean temperatures in the zebrafish’s native India and Bangladesh. Although the lowest observed effect concentration was an order of magnitude above the predicted environmental concentration for clotrimazole, it is conceivable that combined environmental exposures to similarly acting chemicals (e.g. other azole compounds used in crop protection, veterinary and human medicine) could produce similar effects to those we observed. The consequent effects of sex ratios skews and reduced fitness (fecundity and embryo viability) on per capita population growth rate (r) and extinction probability were predicted in inbred versus outbred zebrafish populations using stochastic population viability analysis. The results showed that the observed male-skews >80% threaten small zebrafish populations with fewer than 100 breeding adults (<20 adult females). However, small reductions of 2-3% in embryo-juvenile (age 0+) survivorship (including simulated inbreeding depression) were more influential on r and extinction probability than large sex ratio skews and/or reduced female fecundity. The results presented in this thesis support the contention that chemical effects may be exacerbated by other environmental stressors, but also illustrate the importance of considering biological (genetic), as well as physical and chemical interactions in cumulative ERA. Greater sensitivity of inbred versus outbred organisms to the effects of environmental stressors on sexual differentiation and reproductive fitness offers a margin of safety to ERA and the protection of wildlife populations (excluding those that are severely inbred and critically endangered). This is because, as originally stated, laboratory organisms used in ERA are generally more inbred than their wild counterparts. Nevertheless, more attention should be paid to the origin, breeding history and genetics of laboratory strains. This will help to ensure consistency between studies and testing laboratories and provide more confidence in extrapolating the results to wild populations.

This thesis aimed to understand the mechanisms underlying within-host interactions among coinfecting parasites in wild rodents, how they are affected by the host immune response, and how they contribute to shape disease dynamics in nature. Coinfection is ubiquitous in human, domestic and wild animal populations, and can consist of both microparasites (viruses, bacteria and protozoa) and macroparasites (parasitic helminths). Moreover, coinfecting parasites can interact with each other in a number of ways (positive or negative, direct or indirect), which affects disease severity and progression, parasite transmission, the response of target and non-target parasites to treatment and, ultimately, the epidemiology of each coinfecting parasite species. While previous work on laboratory animals has generated detailed knowledge of the cellular components of the host immune response involved during coinfection, we still mostly lack a conceptual understanding of the role of the host immune response in mediating within-host interactions in nature. I used a known within-host interaction between two important intestinal parasites (the nematode Heligmosomoides polygyrus and the protozoan Eimeria hungaryensis) of wild wood mice (Apodemus sylvaticus) to study the underlying causes and consequences of this interaction for both parasite dynamics and host health. I first investigated if specific and total antibody levels can explain natural burdens and infection of H. polygyrus and Eimeria spp. in the context of other parasites and variation in host demography in a cross-sectional field study. I found that H. polygyrus-specific IgG1 and total faecal IgA were the strongest predictors of both H. polygyrus infection and burden and Eimeria spp. infection. Further, Eimeria spp. infection was associated with lower antibody levels, suggesting an interaction between Eimeria spp. and anti-helminth immunity. Next, I tested the causative relationship between antibody levels and parasite infection. Over the course of a longitudinal anthelmintic treatment study in the field, I measured infection and burden of both target and non-target parasites, as wells as specific and general antibody levels. I found that treatment successfully reduced H. polygyrus burden, wild led to a change in both antibody levels and E. hungaryensis dynamics. Further, H. polygyrus-specific IgG1 levels were predicted by pre-treatment H. polygyrus burden, suggesting that helminth infection induces antibody production, rather than vice versa. Following from this, I explored if treatment of single or multiple parasite groups (helminths, coccidia or both) had an effect on host survival. I used data from a longitudinal field study spanning an entire season of A. sylvaticus (April-December), where animals were given either Ivermectin (anthelmintic), Vecoxan (anti-coccidial), a mix of both drugs or water every fortnight. Ivermectin treatment led to a consistent reduction in H. polygyrus prevalence and burden, as well as a steady increase in E. hungaryensis prevalence, whereas Vecoxan treatment failed to show any effect on either target or non-target parasites. Interestingly, anthelmintic treatment led to a reduction in survival at intermediate H. polygyrus burdens, suggesting that anti-parasite treatments might not always be beneficial for the host. By bringing this wild coinfection system into the lab, I examined if the interaction between H. polygyrus and E. hungaryensis could be re-created under controlled laboratory condition, and if the lack of environmental variation had an effect on parasite and/or antibody dynamics. I found that coinfection led to a delay in H. polygyrus expulsion, and decreased E. hungaryensis shedding during chronic helminth infection. However, coinfection did not affect antibody dynamics. This not only demonstrated that the interaction between the two parasites was reciprocal, but also showed that coinfection can significantly affect parasite transmission dynamics. In an ongoing bioinformatic analysis, I investigated the level of genetic diversity in wild Eimeria spp. populations in order to uncover the mechanism underlying a common lack of protective immunity towards Eimeria spp. infections in wild and domestic animal populations. I found that there were multiple genetically distinct strains circulating within all populations tested, but homologous re-infection was not less likely than heterologous reinfection. This suggests that the lack of protective immunity in wild Eimeria spp. Populations cannot solely be explained by high levels of genetic diversity. This thesis provides several important insights into the mechanisms underlying parasite within-host interactions. Importantly, it highlights that, whilst host immunity plays a crucial role in determining the outcome of coinfection, other factors such as host demography have to be taken into account in order to understand the interplay between immunity and coinfection. I further show that anti-parasite treatments in the wild can be successful, but the benefits of such treatments can be context dependent. More broadly, my findings can have important implications for the planning and evaluation of treatment programs targeted at both single and coinfected animals and humans in their natural environment.

Thesis (M.A. (Industrial Psychology))--North-West University, Potchefstroom Campus, 2007.

By developing strong, self-sustaining individuals in organisations, employees will need to withstand the forces of stressors and be able to cope with continuous changes within their working environment. To move the equilibrium level from the current to the desired condition, the field of forces must be altered - by adding driving forces and by removing restraining forces. An individual's sense of coherence may either alleviate or aggravate reactions to a stressor and moderate the impact of occupational stressors on the individual's affective outcomes. The objectives of this study were to validate the 13-item version of the Orientation to Life Questionnaire (OLQ) (Antonovsky, 1987) and to determine the experience of employees with high levels of sense of coherence regarding helping and restraining factors within the workplace (compared to that of those with a low sense of coherence). A cross-sectional s w e y design was used. The total population (N = 2 678) of employees in a financial institution in Gauteng was used in this study. Random samples of groups with a strong (n = 300) and low (n = 300) sense of coherence were taken for purposes of the qualitative study. The OLQ (Antonovsky, 1987) and a biographical questionnaire were administered. The scale showed acceptable reliability and construct validity. The study set out to determine the applicability of the theoretical model of sense of coherence to employees in a financial institution. Reliability analysis revealed that the three subscales of sense of coherence were sufficiently internally consistent. The reliability of the measuring instrument were assessed with the use of Cronbach alpha coefficients. Descriptive statistics (e.g. mean and standard deviations) were used to analyse the data. By using the structural equation modelling approach, a one-dimensional factor structure for sense of coherence amongst employees in a financial institution emerged. The reliability analysis revealed that the alpha scores were acceptable. It can therefore be concluded that the 13-item version of the OLQ is a reliable and valid measuring instrument. The results showed that although employee groups with high and low levels of sense of coherence are experiencing similar helping and restraining factors within their working environment, helping factors are being experienced with a higher frequency by groups with high levels of sense of coherence and restraining factors with a higher frequency by groups with low levels of sense of coherence. Recommendations were made for future research. / Thesis (M.A. (Industrial Psychology))--North-West University, Potchefstroom Campus, 2007

Chez les pollinisateurs sociaux, comme l'abeille domestique (Apis mellifera L.) et le bourdon terrestre (Bombus terrestris L.), mes deux modèles d'étude, différents individus sont spécialisés dans différentes tâches. Il est admis que différents types de comportement de butinage contribuent à une optimisation des performances de la colonie. Actuellement, les populations de pollinisateurs sont exposées à des stress environnementaux, qui sont connus pour perturber le comportement des individus en visant directement leur cognition. Il est ainsi crucial de mieux comprendre comment les colonies d'abeilles et de bourdons maintiennent une activité de butinage efficace, et quels sont les effets de stress environnementaux sur les butineuses. Dans cette thèse, j'ai donc examiné les différentes stratégies de butinage pour différentes sources de nourriture, pollen et nectar, et les variabilités interindividuelles dans le comportement de butinage. Je me suis aussi intéressé à l'impact de stress tels que les pesticides sur l'efficacité de butinage. J'ai utilisé la technologie RFID pour suivre le comportement des abeilles tout au long de leur vie. J'ai trouvé que les colonies d'abeilles et de bourdons reposent sur un petit groupe d'individus très actifs qui fournissent la majorité de la nourriture pour la colonie. Chez les abeilles, ces individus très actifs sont aussi plus efficaces pour collecter nectar et pollen. J'ai aussi identifié l'existence de différentes stratégies pour la collecte de pollen ou de nectar. Ensuite, j'ai pu montrer que les bourdons ont des différences interindividuelles très marquées dans un test de navigation, une tâche cruciale dans le comportement de butinage. Finalement, j'ai testé l'effet néfaste de pesticides sur l'apprentissage visuel chez l'abeille. Cette thèse a pour but de mieux comprendre les causes de vulnérabilité des pollinisateurs aux stress environnementaux. Mes résultats soulignent le besoin de considérer la diversité comportementale comme une adaptation des espèces de pollinisateurs sociaux, mais aussi comme une potentielle cause de vulnérabilité de la colonie vis-à-vis des stress. / In social insects, such as bees, different individuals specialise in the collection of different resources, and it is assumed that natural behavioural variability among foragers contributes to a self-organised optimisation of colony performance. Currently, bee populations are facing an increasing number of environmental stressors, known to disturb the behaviour of individuals, presumably upon their impact on cognitive capacities. Hence it is important to learn more about how stressors impact on individual foraging behaviour to understand how a colony maintains effective nutrition and development. In this thesis in cognitive ecology, I examined the different foraging strategies for the different macronutrient sources, pollen and nectar, and the inter-individual variation in bee foraging performance. I also looked at how stressors, such as pesticides, can impact on bee foraging efficiency. I compared two social Hymenoptera that vary in their level of social complexity: the European honey bee (Apis mellifera L.) and the buffed-tailed bumblebee (Bombus terrestris L.). I used Radio Frequency Identification (RFID) to automatically track the foraging behaviour of bees throughout their life. I found that honey bee and bumblebee colonies rely on a subset of very active bees to supply the whole colony needs. In honey bees, these foragers are more efficient and collect more pollen. I also identified different strategies for pollen or nectar collection in both species. Using manipulative experiments, I then showed that bees exhibit consistent inter-individual different behaviours in a spatial learning task and that pesticides impair visual learning. My thesis aims at better explaining the causes of vulnerability of pollinators to sublethal pesticides and other environmental stressors. The results highlight the need for considering behavioural diversity as an adaptation for social insects, as well as a potential dimension of colony-level vulnerability to environmental stressors that can impair the whole colony nutritional balance.

Above-ground biomass was allometrically estimated to quantify the amount of mangrove species in selected quadrats of Xuan Thuy National Park. Physicochemical properties of surrounding waters and soils were measured and treated stochastically by correlational analysis with estimated biomass values. Correlation results suggested that qualities of surrounding waters and soils are not the principal inhibitors of mangrove growth in Xuan Thuy. The available historical records infer that the main factor of mangrove loss in the past lay on land reclamation for shrimp aquaculture. In addition, results of correlation analysis showed geographical coincidence of mangrove fragmentation with influence area of water channeling used for aquaculture activities. Furthermore, the distribution of anomalous values of metals concentration was corresponding with anthropological activities associated to clam aquaculture and sand extraction. Based on the aforementioned analysis and the information on anthropological activities in the buffer zone of Xuan Thuy, were provided basic information on inherent environmental stressors of ecosystems in Xuan Thuy National Park. / Sinh khối trên mặt đất đã được ước tính theo phương pháp tương quan sinh trưởng để đưa ra số lượng các loài đước trong các mẫu vuông được lựa chọn tại Vườn quốc gia Xuân Thủy. Các đặc tính hóa-lí của những vùng nước và đất xung quanh đã được đo đạc và xử lí ngẫu nhiên bằng cách phân tích tương quan với những giá trị sinh khối ước tính. Kết quả tương quan cho thấy rằng chất lượng nước và đất xung quanh không phải là những thước đo chính cho tốc độ phát triển cây đước ở Xuân Thủy. Những ghi chép cũ đã kết luận rằng việc sử dụng đất để nuôi tôm là tác nhân chính dẫn tới suy giảm loài đước trong quá khứ. Bên cạnh đó, kết quả phân tích tương quan cho thấy sựtrùng hợp về mặt địa lý giữa sự phân mảnh của loài đước và những vùng nước bị ảnh hưởng do việc nuôi trồng thủy sản. Hơn nữa, sự phân bố bất thường của các giá trị đo mức độ tập trung kim loại cũng tương ứng với các hoạt động nuôi trồng thủy sản và khai thác cát của con người. Những phân tích nêu trên và nghiên cứu về hoạt động của con người tại vùng đệm của Xuân Thủy sẽ cung cấp những thông tin cơ bản về những mối đe dọa môi trường hệ sinh thái tại Vườn Quốc Gia Xuân Thủy.

Lake Winnipeg has been subject to intense eutrophication and invasive species such as Rainbow Smelt and Eubosmina coregoni for the last 40 years. This study demonstrated significant increases in total phosphorus, total nitrogen, chlorophyll-a, overall zooplankton abundance, and specifically Cladocera, between 1969 and the first decade of the 21st century. There were specific basin differences in the long-term changes of the Cladocera community, with the species Chydorus sphaericus and Ceriodaphnia quadrangula negatively affected by high levels of phosphorus, nitrogen and chlorophyll-a. Moreover, long-term change in the Cladocera community composition and abundance throughout the years (1969-2011) during summer was correlated with intensifying eutrophication. Additionally, weak diel vertical migration in the zooplankton community was observed for the first time in Lake Winnipeg.

Lake Winnipeg has been subject to intense eutrophication and invasive species such as Rainbow Smelt and Eubosmina coregoni for the last 40 years. This study demonstrated significant increases in total phosphorus, total nitrogen, chlorophyll-a, overall zooplankton abundance, and specifically Cladocera, between 1969 and the first decade of the 21st century. There were specific basin differences in the long-term changes of the Cladocera community, with the species Chydorus sphaericus and Ceriodaphnia quadrangula negatively affected by high levels of phosphorus, nitrogen and chlorophyll-a. Moreover, long-term change in the Cladocera community composition and abundance throughout the years (1969-2011) during summer was correlated with intensifying eutrophication. Additionally, weak diel vertical migration in the zooplankton community was observed for the first time in Lake Winnipeg.

The increasing globalization of elite soccer match-play means that soccer players are likely to compete in hot, hypoxic and hot-hypoxic environments over a season. Soccer match-play studies have identified a marked decline in soccer-specific physical performance in the heat and hypoxia due to increasing body temperatures and a reduction in partial pressure of oxygen (PO2), respectively. As hot environments are more prevalent in elite soccer match-play, cooling strategies have been assessed within the literature in an attempt to alleviate these heat-induced- decrements. However, utilising a soccer match-play design makes environmental and interventional inferences difficult to ascertain, as a plethora of match factors and adaptive pacing strategies cause high variability in key physical performance measures within soccer match-play. Therefore, the three experiments within thesis aimed to assess the reliability and validity of a non-motorised treadmill (NMT) based soccer-specific simulation [intermittent Soccer Performance Test - (iSPT)], to enable the reliable investigation of environmental stress on soccer performance and the efficacy of pre- and half-time-cooling to attenuate any heat- induced-decrements. The purpose of experiment 1 was to investigate the reliability and validity of iSPT which utilised a novel speed component called a ‘variable run’. This speed component quantified the distance covered at a self-selected speed above the second ventilatory threshold (VT2speed), which attempted to delimit a ‘high-intensity’ threshold. Twenty male University soccer players completed one maximal oxygen (O2) uptake (V̇ O2max ) test, three familiarisation (FAM) sessions and one peak speed assessment (PSA) on the NMT, before completing the iSPT twice (iSPT1 and iSPT2). The total distance, sprint distance and high-speed distance covered were 8,952 ± 476 m, 1,000 ± 74 m and 2156 ± 140 m, respectively. No significant difference (p>0.05) was found between repeated trials of the iSPT for all physical performance measures and physiological responses. Reliability measures between iSPT1 and iSPT2 showed good agreement [Coefficient of variation: <4.6%; Intraclass correlation: >0.80] compared with statistical guidelines. Furthermore, the variable run phase showed high speed running capacity was significantly decreased (p<0.05) in the last 15 min compared to the first 15 min, showing parity with previous match-play data. Experiment 1 validated the iSPT as a NMT based soccer- specific simulation compared to previous match-play data, and is a reliable tool for assessing and monitoring the physical performance and physiological responses in soccer players. Successfully completing the aim of experiment 1 facilitated the quantification of hot (HOT), hypoxia (HYP) and hot-hypoxia (HH) mediated decrements on maximal soccer-specific performance in experiment 2. Twelve male University soccer players completed three FAM sessions, one PSA and four randomised crossover experimental trials of the intermittent Soccer Performance Test (iSPT) in normoxic-temperate (CON: 18oC 50% rH), HOT (30oC; 50% rH), HYP (1,000m; 18oC 50% rH) and HH (1,000m; 30oC; 50% rH). Physical performance and its performance decrements, body temperatures [rectal (Tre), skin (Tsk) and estimated muscle temperature (Tmu)], heart rate (HR), arterial blood oxygen saturation (SaO2), perceived exertion, thermal sensation (TS), body mass changes, blood lactate (Bla) and plasma volume were all measured. Performance decrements were similar in HOT and HYP [total distance (-4%), high- speed distance (~-8%) and variable run distance (~-12%) covered] and exacerbated in HH [total distance (-9%), high-speed distance (-15%) and variable run distance (-15%)] compared to CON. A 4% increase in peak sprint speed was present in HOT compared with CON and HYP and 7% greater in HH. The sprint distance covered was unchanged (p > 0.05) in HOT and HYP and only decreased in HH (-8%) compared with CON. Body mass (-2%), temperatures (+2- 5%) and TS (+18%) were altered in HOT. Furthermore, SaO2 (-8%) and HR (+3%) were changed in HYP. Similar changes in body mass and temperatures, HR, TS and SaO2 were evident in HH compared to HOT and HYP, however, Bla (p < 0.001) and plasma volume (p <0.001) were only significantly altered in HH. Perceived exertion was elevated (p < 0.05) by 7% in all conditions compared with CON. Regression analysis identified that absolute TS and absolute rise in Tsk and estimated Tmu (r = 0.82, r = 0.84 r = 0.82, respectively; p <0.05) predicted the hot-mediated-decrements in HOT. The hot, hypoxic and hot-hypoxic environments impaired physical performance during iSPT. Future interventions should address the increases in TS and body temperatures, to attenuate these decrements in physical performance. Experiment 3 of this thesis aimed to identify three pre- and half-time-cooling strategies to attenuate the heat-induced-decrements previously seen in experiment 2. Eight male University soccer players completed four randomised experimental trials of iSPT, three with cooling and one control (i.e. No pre- or half-time cooling: CON). The pre- and half-time-cooling interventions involved were 30-min or 15 min in duration, respectively. Ice slurry ingestion (SLURRY), ice packs (PACKS) covering the upper legs and mixed-methods (MM: PACKS and SLURRY) were utilised as the three cooling interventions. Physical performance and its performance decrements, body temperatures (Tre, Tsk and estimated Tmu), HR, perceived exertion, TS, body mass changes and Bla were all measured. Compared with CON, both PACKS and SLURRY pre-cooling significantly reduced (p > 0.05) central (Tre) and peripheral (Tsk and estimated Tmu) body temperatures prior to iSPT, respectively. However, body temperature and physical performance were unchanged during the first half of PACKS and SLURRY compared with CON. The MM pre-cooling significantly reduced all body temperatures and TS both prior to and during the first half which coincided with an improvement in total distance (+3%), high-speed distance (+4%) and variable run distance (+5%) covered. Half-time-cooling via PACKS, SLURRY and MM had no ergogenic effect (p> 0.05) upon physical performance in the second half, compared with CON. The 30 min of mixed-method pre-cooling, via ice packs placed upon the upper legs and ice slurry ingestion, significantly improved simulated soccer performance during the first half, however, future research should identify a valid half-time-cooling strategy to offer further improvements to physical performance in the second half. The main findings within this thesis revealed that the iSPT showed validity with previous soccer match-play data and strong reproducibility between two tests (iSPT1 and iSPT2). Furthermore, the variable run component showed efficacy as sensitive measure of the decrements in high-speed running capability. As the iSPT demonstrated low test-retest error compared with the statistical guidelines and previous NMT based soccer-specific simulations, any changes to physical performance can be attributed to an intervention and not the variability of the measure, unlike in soccer match-play situations. No difference was seen for all physical performance measures in both HOT and HYP, however, the heat and hypoxic-induced- decrements stem from increasing body temperatures and changes to both SaO2 and HR, respectively. Such decrements may have a detrimental effect upon the match outcome. These heat-induced-decrements were attenuated in the first half after 30 min of mixed-methods pre- cooling, however, the 15 min of mixed-methods half-time-cooling did not significantly improve any physical performance measure in the second half. The mixed-method pre-cooling strategy tested within this thesis could go some way in maintaining physical performance during the first half of soccer match-play in hot environments (~30oC). However, future laboratory based research within a controlled environment should look to assess different combinations, times and strategies of cooling which may be applicable to the time constraints associated with elite soccer.