The effect of medium-term heat acclimation on endurance performance in a temperate environment

We investigated whether an 11-day heat acclimation programme (HA) enhanced endurance performance in a temperate environment, and the mechanisms underpinning any ergogenic effect. Twenty-four males (V̇O2max: 56.7±7.5 mL∙kg-1∙min-1) completed either: i) HA consisting of 11 consecutive daily exercise sessions (60-90 minutes·day-1; n=16) in a hot environment (40°C, 50% RH) or; ii) duration and exertion matched exercise in cool conditions (CON; n=8 [11°C, 60% RH]). Before and after each programme power at lactate threshold, mechanical efficiency, VO2max, peak power output (PPO) and work done during a 30-minute cycle trial (T30) were determined under temperate conditions (22°C, 50% RH). HA reduced resting (-0.34±0.30°C) and exercising (-0.43±0.30°C) rectal temperature, and increased whole-body sweating (+0.37±0.31 L·hr-1) (all P≤0.001), with no change in CON. Plasma volume increased in HA (10.1±7.2%, P<0.001) and CON (7.2±6.3%, P=0.015) with no between-groups difference, whereas exercise heart rate reduced in both groups, but to a greater extent in HA (-20±11 b·min-1) than CON (-6±4 b·min-1). VO2max, lactate threshold and mechanical efficiency were unaffected by HA. PPO increased in both groups (+14±18W), but this was not related to alterations in any of the performance or thermal variables, and T30 performance was unchanged in either group (HA: Pre=417±90 vs. Post=427±83 kJ; CON: Pre=418±63 vs. Post=423±56 kJ). In conclusion, 11-days HA induces thermophysiological adaptations, but does not alter the key determinants of endurance performance. In trained males, the effect of HA on endurance performance in temperate conditions is no greater than that elicited by exertion and duration matched exercise training in cool conditions

Inter-individual variation in the adaptive response to heat acclimation

Aim: To investigate inter-individual variance in adaptive responses to heat acclimation (HA).Methods: 17 males (VO2max=58.8(8.4) ml·kg-1·min-1) undertook 10-days (exercise + heat stress [40°C, 50%RH]) HA. Adaptation was assessed by heat stress tests (HST; 60–minutes cycling, 35% peak power output) pre- and post-HA. Results: Inter-individual variability was evident in adaptive responses e.g. mean(range) reduction in end-exercise Tre=-0.70(-0.20 to - 1.32)°C, but, in the main, the variance in adaptation was unrelated across indices (thermal sudomotor, cardiovascular, haematological), indicating independence between adaptation indices. Variance in adaptive responses was not correlated with aerobic capacity, history of previous HA, or the accrued thermal-dose. Some responses to the initial HST were related to the subsequent adaptations e.g. ∆T̅sk during the initial HST and the reduction in the within HST ΔTre after HA (r=-0.676), but responses to the initial HST may also have been influenced by HST design e.g. ΔTre correlated with metabolic heat production (r=0.609). Metabolic heat production also correlated with the reduction in the within HST ΔTre after HA (r=-0.514). Summary: HA indices are mainly independent; ‘low’, or ‘high’, responders on one index do not necessarily demonstrate similar response across other indices. Variance in HA responses was not related to aerobic capacity, previous HA, or thermal-dose. Thermo-physiological responses to a HST might identify individuals who will benefit from HA. However, some initial responses are influenced by HST design, which may also affect the scope for demonstrating adaption. Conclusion: Variance in the HA response remains largely unaccounted for and future studies should identify factors contributing to this variance

Inter-individual variation in the adaptive response to heat acclimation; impact on temperate performance

Introduction: Typical heat acclimation (HA) responses are well characterised at the cohort level, however, individual data demonstrate considerable heterogeneity. Recent research suggests that HA indicies are independent and not influenced by aerobic capacity, previous HA or thermal dose. However, some baseline responses may be useful in estimating the potential benefits that an individual may obtain from HA. It remains to be establised whether the extent of individual HA will translate to aspects of individual endurance performance and thermophysiological indicies in temperate conditions, and if these can be related to any prior variables

Effects of acute or chronic heat exposure, exercise and dehydration on plasma cortisol, IL-6 and CRP levels in trained males

This study examined the acute and chronic effects of euhydrated and hypohydrated heat exposure, on biomarkers of stress and inflammation. Eight trained males [mean (SD) age: 21 (3) y; mass: 77.30 (4.88) kg; V̇O2max: 56.9 (7.2) mL·kg−1·min−1] undertook two heat acclimation programmes (balanced cross-over design), once drinking to maintain euhydration and once with restricted fluid-intake (permissive dehydration). Days 1, 6, and 11 were 60 min euhydrated exercise-heat stress tests (40 °C; 50 % RH, 35% peak power output), days 2–5 and 7–10 were 90 min, isothermal-strain (target rectal temperature: 38.5 °C) exercise-heat sessions. Plasma was obtained pre- and post- exercise on day 1, 2, and 11 and analysed for cortisol, interleukin-6 (IL-6), and C-reactive protein (CRP). Cortisol and CRP were also assessed on day 6. IL-6 was elevated following the initial (acute) 90 minute isothermal heat strain exercise-heat exposure (day 2) with permissive dehydration ( (pre exercise: 1.0 pg.mL-1 [0.9], post-exercise: 1.8 pg.mL-1 [1.0], P = 0.032) and when euhydrated (pre-exercise: 1.0 pg.mL-1 [1.4], post-exercise: 1.6 pg.mL-1 [2.1], P = 0.048). Plasma cortisol levels were also elevated but only during permissive dehydration (P = 0.032). Body mass loss was strongly correlated with Δcortisol (r = -0.688, P = 0.003). Although there was a trend for post-exercise cortisol to be decreased following both heat acclimation programmes (chronic effects), there were no within or between intervention differences in IL-6 or CRP. In conclusion, acute exercise in the heat increased IL-6 and cortisol only when fluid-intake is restricted. There were no chronic effects of either intervention on biomarkers of inflammation as evidenced by IL-6 and CRP returning to basal level at the end of heat acclimation

VUV/EUV ionising radiation and atoms and ions: dual laser plasma investigations

The interaction of ionising radiation with atoms and ions is a key fundamental process. This report concentrates on studies of photoexcitation/photoionisation using laser-produced plasmas as continuum sources and synchronised laser plasma plumes to provide the absorbing atom or ion species. Examples from studies of the interaction of ionising radiation with atoms and ions ranging from few-electron atomic and ionic systems to the many-electron high atomic number actinides are reviewed and illustrate the advantages and limitations of the Dual Laser Plasma technique

Review article: the future of microbiome-based therapeutics

Published online 24 May 2022Background: From consumption of fermented foods and probiotics to emerging applications of faecal microbiota transplantation, the health benefit of manipulating the human microbiota has been exploited for millennia. Despite this history, recent technological advances are unlocking the capacity for targeted microbial manipulation as a novel therapeutic.Aim: This review summarises the current developments in microbiome- based medicines and provides insight into the next steps required for therapeutic development.Methods: Here we review current and emerging approaches and assess the capabilities and weaknesses of these technologies to provide safe and effective clinical inter-ventions. Key literature was identified through Pubmed searches with the following key words, ‘microbiome’, ‘microbiome biomarkers’, ‘probiotics’, ‘prebiotics’, ‘synbiotics’, ‘faecal microbiota transplant’, ‘live biotherapeutics’, ‘microbiome mimetics’ and ‘postbiotics’.Results: Improved understanding of the human microbiome and recent technological advances provide an opportunity to develop a new generation of therapies. These therapies will range from dietary interventions, prebiotic supplementations, single probiotic bacterial strains, human donor-derived faecal microbiota transplants, ra-tionally selected combinations of bacterial strains as live biotherapeutics, and the beneficial products or effects produced by bacterial strains, termed microbiome mimetics.Conclusions: Although methods to identify and refine these therapeutics are continually advancing, the rapid emergence of these new approaches necessitates accepted technological and ethical frameworks for measurement, testing, laboratory practices and clinical translation.Emily L. Gulliver, Remy B. Young, Michelle Chonwerawong, Gemma L. D'Adamo, Tamblyn Thomason, James T. Widdop, Emily L. Rutten, Vanessa Rossetto Marcelino, Robert V. Bryant, Samuel P. Costello, Claire L. O'Brien, Georgina L. Hold, Edward M. Giles, Samuel C. Forste

Trends in autoionization of Rydberg states converging to the 4s threshold in the Kr-Rb⁺-Sr²⁺ isoelectonic sequence: theory and experiment

We have measured the photoabsorption spectra of the Kr-like ions Rb+ and Sr2+ at photon energies corresponding to the excitation of 4s-np resonances using, the dual laser plasma photoabsorption technique. Dramatic changes in the line profiles, with increasing ionization and also proceeding along the Rydberg series of each ion, are observed and explained by the trends in 4s-transition amplitudes computed within a framework of configuration-interaction Pauli-Fock calculations. Total photoionization cross sections show very good agreement with relative absorption data extracted from the measured spectra