High-intensity interval training

High-intensity interval training (HIIT) is characterised by brief, intermittent bursts of near- or maximal-intensity exercise, interspersed by periods of active or passive recovery. The limited available evidence suggests that HIIT is an efficacious training method for young athletes. The effect of HIIT on cardiorespiratory fitness (CRF), endurance performance, explosive strength and sport-specific performance has been examined in a range of young athletic populations from various sports. Furthermore, promising preliminary findings suggest that HIIT may confer further benefits to a range of health outcome measures including fasting insulin, lipoproteins, systolic blood pressure and endothelial function; obese youth may benefit particularly from this type of training. Improved cardiorespiratory fitness has been observed consistently after HIIT in athletic and non-athletic populations. Larger studies, extended over longer periods, that include valid measures of exercise compliance, tolerance and enjoyment are required to further delineate the priority that could be afforded to this type of training

Seasonal Heat Acclimatisation in Healthy Adults:A Systematic Review

BACKGROUND: Physiological heat adaptations can be induced following various protocols that use either artificially controlled (i.e. acclimation) or naturally occurring (i.e. acclimatisation) environments. During the summer months in seasonal climates, adequate exposure to outdoor environmental heat stress should lead to transient seasonal heat acclimatisation. OBJECTIVES: The aim of the systematic review was to assess the available literature and characterise seasonal heat acclimatisation during the summer months and identify key factors that influence the magnitude of adaptation. ELIGIBILITY CRITERIA: English language, full-text articles that assessed seasonal heat acclimatisation on the same sample of healthy adults a minimum of 3 months apart were included. DATA SOURCES: Studies were identified using first- and second-order search terms in the databases MEDLINE, SPORTDiscus, CINAHL Plus with Full Text, Scopus and Cochrane, with the last search taking place on 15 July 2021. RISK OF BIAS: Studies were independently assessed by two authors for the risk of bias using a modified version of the McMaster critical review form. DATA EXTRACTION: Data for the following outcome variables were extracted: participant age, sex, body mass, height, body fat percentage, maximal oxygen uptake, time spent exercising outdoors (i.e. intensity, duration, environmental conditions), heat response test (i.e. protocol, time between tests), core temperature, skin temperature, heart rate, whole-body sweat loss, whole-body and local sweat rate, sweat sodium concentration, skin blood flow and plasma volume changes. RESULTS: Twenty-nine studies were included in this systematic review, including 561 participants across eight countries with a mean summer daytime wet-bulb globe temperature (WBGT) of 24.9 °C (range: 19.5–29.8 °C). Two studies reported a reduction in resting core temperature (0.16 °C; p < 0.05), 11 reported an increased sweat rate (range: 0.03–0.53 L·h(−1); p < 0.05), two observed a reduced heart rate during a heat response test (range: 3–8 beats·min(−1); p < 0.05), and six noted a reduced sweat sodium concentration (range: − 22 to − 59%; p < 0.05) following summer. The adaptations were associated with a mean summer WBGT of 25.2 °C (range: 19.6–28.7 °C). LIMITATIONS: The available studies primarily focussed on healthy male adults and demonstrated large differences in the reporting of factors that influence the development of seasonal heat acclimatisation, namely, exposure time and duration, exercise task and environmental conditions. CONCLUSIONS: Seasonal heat acclimatisation is induced across various climates in healthy adults. The magnitude of adaptation is dependent on a combination of environmental and physical activity characteristics. Providing environmental conditions are conducive to adaptation, the duration and intensity of outdoor physical activity, along with the timing of exposures, can influence seasonal heat acclimatisation. Future research should ensure the documentation of these factors to allow for a better characterisation of seasonal heat acclimatisation. PROSPERO REGISTRATION: CRD42020201883. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s40279-022-01677-0

Assessing physical work capacity and performance loss during heat stress using a cardiovascular strain limit model

Assessing physical work capacity and performance loss during heat stress using a cardiovascular strain limit mode

Impact of fan use on physical work capacity in extreme heat

Impact of fan use on physical work capacity in extreme hea

Model experiment of magnetic field amplification in laser-produced plasmas via the Richtmyer-Meshkov instability

A model experiment of magnetic field amplification (MFA) via the Richtmyer-Meshkov instability (RMI) in supernova remnants (SNRs) was performed using a high-power laser. In order to account for very-fast acceleration of cosmic rays observed in SNRs, it is considered that the magnetic field has to be amplified by orders of magnitude from its background level. A possible mechanism for the MFA in SNRs is stretching and mixing of the magnetic field via the RMI when shock waves pass through dense molecular clouds in interstellar media. In order to model the astrophysical phenomenon in laboratories, there are three necessary factors for the RMI to be operative: a shock wave, an external magnetic field, and density inhomogeneity. By irradiating a double-foil target with several laser beams with focal spot displacement under influence of an external magnetic field, shock waves were excited and passed through the density inhomogeneity. Radiative hydrodynamic simulations show that the RMI evolves as the density inhomogeneity is shocked, resulting in higher MFA

E0 Measurements in 154Sm Using SAGE: An Investigation of Collectivity in Rare-Earth Nuclei

Using the Silicon And Germanium array (SAGE) at the University of Jyvaskyla (JYFL), E0 transition strengths in 154Sm were measured as a test case for further measurements in the rare-earth region. A large degree of collectivity is expected in nuclear excitations of even-even rare-earth nuclei and the nature of excited $0^+$ states in these nuclei is of particular interest. SAGE was employed to measure the E0 transition strength of the 0_2^+ -> 0_1^+ and 2_2^+ -> 2_1^+ transitions in $^{154}$Sm. Such transition strengths provide a key observable to differentiate between nuclear models. To facilitate this measurement, peak-fitting techniques were developed to improve the analysis of the particular peak shapes observed in electron spectra from SAGE. A method of background subtraction was developed to remove time-random coincidences using the timing information available from the JYFL total data readout system. An isotopically enriched samarium target was bombarded by a 65 MeV beam of 16O, populating states of interest via Coulomb excitation, after which de-excitation via internal conversion and gamma-ray emission were observed. The 0_2^+ -> 0_1^+ E0 transition could not be measured in this work due to the background found in the current experimental setup. The equally important 2_2^+ -> 2_1^+ E0 transition strength could be studied by implementation of background subtraction to remove false-coincidences. The experiment was normalised by measurement of conversion coefficients for known transitions in 154Sm and in the contaminants 152Sm, 166Yb and 167Yb. An electron peak associated with the 2_2^+ -> 2_1^+ transition in 154Sm was not observable, but a stringent upper-limit was placed on the E0 transition strength. The measurement was compared to the interaction boson model and Bohr and Mottleson collective models and was found to be smaller than predicted by both collective interpretations. The usefulness of SAGE and this measurement technique was proved and the direction for future research in this area is discussed

Exercise and postprandial lipaemia in adolescent boys and girls: a school-based approach

The current thesis aimed to extend previous laboratory-derived research by examining the efficacy of acute exercise performed at school to modulate postprandial lipaemia during adolescence. Ecologically valid forms of exercise were utilised and postprandial experimental measures were conducted under free-living school conditions. Comprised of four translational experimental studies, the current thesis examined the efficacy of school-based exercise interventions and provides empirical evidence to further inform school-based exercise recommendations. [Continues.

High-intensity interval training

This is a draft of a chapter that has been accepted for publication by Oxford University Press in the forthcoming book Paediatric Exercise Science and Medicine edited by N. Armstrong and W. van Mechelen published in 2017.High-intensity interval training (HIIT) is characterised by brief, intermittent bursts of near- or maximal-intensity exercise, interspersed by periods of active or passive recovery. The limited available evidence suggests that HIIT is an efficacious training method for young athletes. The effect of HIIT on cardiorespiratory fitness (CRF), endurance performance, explosive strength and sport-specific performance has been examined in a range of young athletic populations from various sports. Furthermore, promising preliminary findings suggest that HIIT may confer further benefits to a range of health outcome measures including fasting insulin, lipoproteins, systolic blood pressure and endothelial function; obese youth may benefit particularly from this type of training. Improved cardiorespiratory fitness has been observed consistently after HIIT in athletic and non-athletic populations. Larger studies, extended over longer periods, that include valid measures of exercise compliance, tolerance and enjoyment are required to further delineate the priority that could be afforded to this type of training

DATASETS HEATSHIELD project Loughborough University, averaged per condition and individual sessions

The purpose of this study was to investigate which climate/heat indices perform best in predicting heat-induced loss of physical work capacity (PWC-loss). Integrating data from earlier studies, data from 982 exposures (75 conditions) exercising at a fixed cardiovascular load of 130b.min-1, in varying temperatures (15-50°C), humidities (20-80%), solar radiation (0-800W.m-2), wind (0.2-3.5m.s-1) and two clothing levels, were used to model the predictive power of ambient temperature, Universal Thermal Climate Index (UTCI), Wet Bulb Globe Temperature (WBGT), Modified Equivalent Temperature (mPET), Heat Index, Apparent Temperature (AT), and Wet Bulb Temperature (Twb) for the calculation of PWC-loss, skin temperature (Tskin) and core-to-skin temperature gradient, and Thermal perception( TSV) in the heat. R2, RMSD and Akaike stats were used indicating model performance.Indices not including wind/radiation in their calculation (Ta, Heat Index, AT, Twb) struggled to provide consistent predictions across variables. For PWC-loss and TSV, UTCI and WBGT had the highest predictive power. For Tskin, and core-to-skin temperature gradient, the physiological models UTCI and mPET worked best in semi-nude conditions, but clothed, AT, WBGT and UTCI worked best. For all index predictions, Ta, vapor pressure and Twb were shown to be the worst heat strain predictors. While UTCI and WBGT had similar model performance using the full dataset, WBGT did not work appropriately in windy, hot-dry, conditions where WBGT predicted lower strain due to wind, whereas the empirical data, UTCI and mPET indicated that wind in fact increased the overall level of thermal strain. The findings of the current study highlight the advantages of using a physiological model-based index like UTCI when evaluating heat stress in dynamic thermal environments.</p