Environmental stressors and cooling interventions on simulated soccer performance

A thesis submitted to the University of Bedfordshire, in partial fulfilment of therequirements for the degree of Doctor of PhilosophyThe 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: 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

Dynamic critical exponents of Swendsen-Wang and Wolff algorithms by nonequilibrium relaxation

With a nonequilibrium relaxation method, we calculate the dynamic critical exponent z of the two-dimensional Ising model for the Swendsen-Wang and Wolff algorithms. We examine dynamic relaxation processes following a quench from a disordered or an ordered initial state to the critical temperature T_c, and measure the exponential relaxation time of the system energy. For the Swendsen-Wang algorithm with an ordered or a disordered initial state, and for the Wolff algorithm with an ordered initial state, the exponential relaxation time fits well to a logarithmic size dependence up to a lattice size L=8192. For the Wolff algorithm with a disordered initial state, we obtain an effective dynamic exponent z_exp=1.19(2) up to L=2048. For comparison, we also compute the effective dynamic exponents through the integrated correlation times. In addition, an exact result of the Swendsen-Wang dynamic spectrum of a one-dimension Ising chain is derived.Comment: 13 pages, 6 figure

The Prevalence of Metabolic Syndrome and Its Components in Firefighters: A Systematic Review and Meta-Analysis

Previous studies consistently report a high prevalence of cardiovascular disease (CVD) risk factors among firefighters. However, the clustering of CVD risk factors, defined as metabolic syndrome (MetSyn), has received little attention by comparison. Therefore, the aim of this study was to estimate the pooled prevalence of MetSyn among firefighters. Using combinations of free text for 'firefighter' and 'metabolic syndrome', databases were searched for eligible studies. Meta-analyses calculated weighted pooled prevalence estimates with 95% confidence intervals (CI) for MetSyn, its components and overweight/obesity. Univariate meta-regression was performed to explore sources of heterogeneity. Of 1440 articles screened, 25 studies were included in the final analysis. The pooled prevalence of MetSyn in 31,309 firefighters was 22.3% (95% CI: 17.7-27.0%). The prevalences of MetSyn components were hypertension: 39.1%; abdominal obesity: 37.9%; hypertriglyceridemia: 30.2%; dyslipidemia: 30.1%; and hyperglycemia: 21.1%. Overweight and obesity prevalence rates in firefighters were 44.1% and 35.6%, respectively. Meta-regression revealed that decreased risk of bias (RoB) score and increased body mass index (BMI) were positively associated with an increase in MetSyn prevalence. Since one in five firefighters may meet the criteria for MetSyn, novel interventions should be explored to both prevent MetSyn and reduce the onset of CVD risk factors

2-Hour Accelerated Diagnostic Protocol to Assess Patients With Chest Pain Symptoms Using Contemporary Troponins as the Only Biomarker

Objectives The purpose of this study was to determine whether a new accelerated diagnostic protocol (ADP) for possible cardiac chest pain could identify low-risk patients suitable for early discharge (with follow-up shortly after discharge). Background Patients presenting with possible acute coronary syndrome (ACS), who have a low short-term risk of adverse cardiac events may be suitable for early discharge and shorter hospital stays. Methods This prospective observational study tested an ADP that included pre-test probability scoring by the Thrombolysis In Myocardial Infarction (TIMI) score, electrocardiography, and 0 + 2 h values of laboratory troponin I as the sole biomarker. Patients presenting with chest pain due to suspected ACS were included. The primary endpoint was major adverse cardiac event (MACE) within 30 days. Results Of 1,975 patients, 302 (15.3%) had a MACE. The ADP classified 392 patients (20%) as low risk. One (0.25%) of these patients had a MACE, giving the ADP a sensitivity of 99.7% (95% confidence interval [CI]: 98.1% to 99.9%), negative predictive value of 99.7% (95% CI: 98.6% to 100.0%), specificity of 23.4% (95% CI: 21.4% to 25.4%), and positive predictive value of 19.0% (95% CI: 17.2% to 21.0%). Many ADP negative patients had further investigations (74.1%), and therapeutic (18.3%) or procedural (2.0%) interventions during the initial hospital attendance and/or 30-day follow-up. Conclusions Using the ADP, a large group of patients was successfully identified as at low short-term risk of a MACE and therefore suitable for rapid discharge from the emergency department with early follow-up. This approach could decrease the observation period required for some patients with chest pain. (An observational study of the diagnostic utility of an accelerated diagnostic protocol using contemporary central laboratory cardiac troponin in the assessment of patients presenting to two Australasian hospitals with chest pain of possible cardiac origin; ACTRN12611001069943

Personalized diagnosis in suspected myocardial infarction

Background: In suspected myocardial infarction (MI), guidelines recommend using high-sensitivity cardiac troponin (hscTn)- based approaches. These require fixed assay-specific thresholds and timepoints, without directly integrating clinical information. Using machine-learning techniques including hs-cTn and clinical routine variables, we aimed to build a digital tool to directly estimate the individual probability of MI, allowing for numerous hs-cTn assays. Methods: In 2,575 patients presenting to the emergency department with suspected MI, two ensembles of machine-learning models using single or serial concentrations of six different hs-cTn assays were derived to estimate the individual MI probability ( ARTEMIS model). Discriminative performance of the models was assessed using area under the receiver operating characteristic curve (AUC) and logLoss. Model performance was validated in an external cohort with 1688 patients and tested for global generalizability in 13 international cohorts with 23,411 patients. Results: Eleven routinely available variables including age, sex, cardiovascular risk factors, electrocardiography, and hs-cTn were included in the ARTEMIS models. In the validation and generalization cohorts, excellent discriminative performance was confirmed, superior to hs-cTn only. For the serial hs-cTn measurement model, AUC ranged from 0.92 to 0.98. Good calibration was observed. Using a single hs-cTn measurement, the ARTEMIS model allowed direct rule-out of MI with very high and similar safety but up to tripled efficiency compared to the guideline- recommended strategy. Conclusion We developed and validated diagnostic models to accurately estimate the individual probability of MI, which allow for variable hs-cTn use and flexible timing of resampling. Their digital application may provide rapid, safe and efficient personalized patient care

MODELLING THE SPREAD OF PNEUMONIA IN THE PHILIPPINES USING SUSCEPTIBLE-INFECTED-RECOVERED (SIR) MODEL WITH DEMOGRAPHIC CHANGES

Epidemic modeling is an important tool used by mathematicians in analyzing the rate of spread of an epidemic by taking in account of the parameters and vectors that facilitate the transmission rate of the disease. The measurement of the average transmission rate through mathematical analysis helps in finding the proper approach of disease control methods in mitigating the spread of diseases. The study aims to analyze and predict the rate of transmission of the global epidemic pneumonia in the Philippines population through epidemic modeling. The study methodology used the standard epidemic model known as the SIR model to quantify real-world data on pneumonia cases into a set of differential equations while taking in consideration of changes in the population experienced due to demographic change. The study yielded results that suggested positive correlation in real-world data and the modeled data points mostly for SIR models that assumed linear change in the infection rate and recovery rate. In addition, the implementation of population models showed increases in the infection rate and the recovery rate due to increasing trend observed in the given population. The study evaluated linear rate SIR assuming exponential population growth as the most applicable epidemic model from the selection in modeling real-world epidemic data. In addition, the study compared the effectiveness of using quarantine method and vaccination method in mitigating the spread of pneumonia

Families and religions : conflictand changein modern society

320 p.; 22 cm