Thermoregulatory responses to combined moderate heat stress and hypoxia

Objective: The aim of this study was to examine the cutaneous vascular and sudomotor responses to combined moderate passive heat stress and normobaric hypoxia. Method: Thirteen healthy young males, dressed in a water-perfused suit, underwent passive heating (Δcore temperature ~0.7 °C) twice (NORMOXIA; 20.9% O2 and HYPOXIA; 13% O2). Chest and forearm skin blood flow (SkBF; laser Doppler flux), local sweat rate (SR; capacitance hygrometry) and core (intestinal pill) and skin temperatures, were recorded. Results: HYPOXIA reduced baseline oxygen saturation (98±1 vs. 89±6%, P<0.001) and elevated chest (P=0.03) and forearm SkBF (P=0.03) and HR (64±9 vs. 69±8 beats.min-1, P<0.01). During heating, mean body temperature (T ̅BODY) thresholds for SkBF (P=0.41) and SR (P=0.28) elevations were not different between trials. The SkBF: T ̅BODY linear sensitivity during the initial phase of heating was lower at the Chest (P=0.035) but not different at the forearm (P=0.17) during HYPOXIA. With increasing levels of heating chest SkBF was not different (P=0.55) but forearm SkBF was lower on the forearm (P<0.01) during HYPOXIA. Chest (P=0.85) and forearm (P=0.79) SR:T ̅BODY linear sensitivities were not different between trials. Conclusion: Whilst sudomotor responses and the initiation of cutaneous blood flow elevations are unaffected, hypoxia differentially effects regional SkBF responses during moderate passive heating

Historical reviews of the assessment of human cardiovascular function: interrogation and understanding of the control of skin blood flow.

Several techniques exist for the determination of skin blood flow that have historically been used in the investigation of thermoregulatory control of skin blood flow, and more recently, in clinical assessments or as an index of global vascular function. Skin blood flow measurement techniques differ in their methodology and their strengths and limitations. To examine the historical development of techniques for assessing skin blood flow by describing the origin, basic principles, and important aspects of each procedure and to provide recommendations for best practise. Venous occlusion plethysmography was one of the earliest techniques to intermittently index a limb's skin blood flow under conditions in which local muscle blood flow does not change. The introduction of laser Doppler flowmetry provided a method that continuously records an index of skin blood flow (red cell flux) (albeit from a relatively small skin area) that requires normalisation due to high site-to-site variability. The subsequent development of laser Doppler and laser speckle imaging techniques allows the mapping of skin blood flow from larger surface areas and the visualisation of capillary filling from the dermal plexus in two dimensions. The use of iontophoresis or intradermal microdialysis in conjunction with laser Doppler methods allows for the local delivery of pharmacological agents to interrogate the local and neural control of skin blood flow. The recent development of optical coherence tomography promises further advances in assessment of the skin circulation via three-dimensional imaging of the skin microvasculature for quantification of vessel diameter and vessel recruitment

REPEATED WARM WATER IMMERSION INDUCES SIMILAR CEREBROVASCULAR ADAPTATIONS TO 8-WEEKS OF MODERATE-INTENSITY EXERCISE TRAINING IN FEMALES

Exercise training has potential to positively impact cerebrovascular function in healthy and diseased individuals. Passive heat training using warm water immersion has recently been shown to enhance systemic vascular function including the cerebrovascular response to heating. We suggest that a passive heating intervention can be a useful adjunct or alternative to exercise training. Our aim was to directly compare the effects of exercise with warm water immersion training on cerebrovascular and thermoregulatory function. 18 females (25±5y) performed 8-weeks of moderate-intensity cycling (70% HRmax) or warm-water immersion (42°C) for 30 min three times per week. Brachial artery flow-mediated dilation (FMD) and cardiorespiratory fitness were measured prior to and following both interventions. A passive heat stress was employed to obtain temperature thresholds (Tb) and sensitivities for chest and forearm sweat rate (SR) and cutaneous vasodilation (CVC). Middle cerebral artery velocity (MCAv) was measured at rest and throughout heat stress. FMD (P=0.003) and VO2peak (P<0.001) improved following both interventions. MCAv and cerebrovascular conductance were higher at rest (P<0.001 and 0.05, respectively) and during passive heating (P<0.001 and <0.001, respectively) following both interventions. Chest and forearm SR occurred at a lower Tb post-intervention with no difference between interventions. Chest and forearm SR sensitivity were increased after both interventions with no differences between interventions at the forearm but a larger increase at the chest (P<0.001) following water immersion compared to exercise training. Chest and forearm CVC occurred at a lower Tb (P<0.001) following both interventions with no differences between interventions or over time. Warm water immersion training elicits favourable and similar cerebrovascular, conduit- and thermoregulatory adaptations compared to a period of moderate-intensity exercise training over 8-weeks

Corporate reputation past and future: a review and integration of existing literature and a framework for future research

The concept of corporate reputation is steadily growing in interest among management researchers and practitioners. In this article, we trace key milestones in the development of reputation literature over the past six decades to suggest important research gaps as well as to provide contextual background for a subsequent integration of approaches and future outlook. In particular we explore the need for better categorised outcomes; a wider range of causes; and a deeper understanding of contingencies and moderators to advance the field beyond its current state while also taking account of developments in the macro business environment. The article concludes by presenting a novel reputation framework that integrates insights from reputation theory and studies, outlines gaps in knowledge and offers directions for future research

EXERCISE TRAINING REDUCES THE FREQUENCY OF MENOPAUSAL HOT FLUSHES BY IMPROVING THERMOREGULATORY CONTROL

Objectives: Post-menopausal hot flushes occur due to a reduction in oestrogen production causing thermoregulatory and vascular dysfunction. Exercise training enhances thermoregulatory control of sweating, skin and brain blood flow. We aimed to determine if improving thermoregulatory control and vascular function with exercise training alleviated hot flushes. Methods: Twenty one symptomatic females completed a 7-day hot flush questionnaire and underwent brachial artery flow-mediated dilation and a cardiorespiratory fitness test. Sweat rate and skin blood flow temperature thresholds and sensitivities, and middle cerebral artery velocity (MCAv) was measured during passive heating. Females performed 16-weeks of supervised exercise training or control, and measurements were repeated. Results: There was a greater improvement in cardiorespiratory fitness (4.45 ml•kg-1•min-1 (95% CI: 1.87, 8.16; P=0.04) and reduced hot flush frequency [48 hot flushes•week (39, 56) P<0.001] following exercise compared to control. Exercise reduced basal core temperature [0.14°C (0.01, 0.27) P=0.03] and increased basal MCAv [2.8 cm/s (1.0 to 5.2) P=0.04] compared to control. Sweat rate and skin blood flow thresholds occurred ~0.19 and 0.17°C earlier, alongside improved sweating sensitivity with exercise. MCAv decreased during heating [P<0.005], but was maintained 4.5 cm/s (3.6, 5.5 P<0.005) higher during heating following exercise compared to control [0.6 cm/s (-0.4, 1.4)]. Conclusions: Exercise training that improves cardiorespiratory fitness reduces self-reported hot flushes. Improvements are likely mediated through greater thermoregulatory control in response to increases in core temperature and enhanced vascular function in the cutaneous and cerebral circulations

Corporate law and governance

This chapter surveys the theoretical and empirical research on the main mechanisms of corporate law and governance, discusses the main legal and regulatory institutions in different countries, and examines the comparative governance literature. Corporate governance is concerned with the reconciliation of conflicts of interest between various corporate claimholders and the resolution of collective action problems among dispersed investors. A fundamental dilemma of corporate governance emerges from this overview: large shareholder intervention needs to be regulated to guarantee better small investor protection; but this may increase managerial discretion and scope for abuse. Alternative methods of limiting abuse have yet to be proven effective

Localised cutaneous microvascular adaptation to exercise training in humans

Purpose. Exercise training induces adaptation in conduit and resistance arteries in humans, partly as a consequence of repeated elevation in blood flow and shear stress. The stimuli associated with intrinsic cutaneous microvascular adaptation to exercise training have been less comprehensively studied. Methods. We studied subjects who completed 8-weeks cycle ergometer training, with partial cuff inflation on one forearm to unilaterally attenuate cutaneous blood flow responses during each exercise-training bout. Before and after training, bilateral forearm skin microvascular dilation was determined using cutaneous vascular conductance (CVC: skin flux/blood pressure) responses to gradual localised heater disk stimulation performed at rest (33, 40, 42 and 44°C). Results. Cycle exercise induced significant increases in forearm cutaneous flux and temperature, which were attenuated in the cuffed arm (2-way ANOVA interaction-effect; P<0.01). We found that forearm CVC at 42°C and 44°C was significantly lower in the uncuffed arm following 8-weeks of cycle training (P<0.01), whereas no changes were apparent in the contralateral cuffed arm (P=0.77, interaction-effect P=0.01). Conclusions. Lower limb exercise training in healthy young men leads to lower CVC-responses to a local heating stimulus, an adaptation mediated, at least partly, by a mechanism related to episodic increases in skin blood flow and/or skin temperature

7 days of L-citrulline supplementation does not improve running performance in the heat whilst in a hypohydrated state

Purpose7 days L-citrulline supplementation has been reported to improve blood pressure, V. mathop { text{V}} limits {.} O2 kinetics, gastrointestinal (GI) perfusion and endurance cycling performance through increasing arterial blood flow. In situations where blood volume is compromised (e.g., hyperthermia/hypohydration), L-citrulline may improve thermoregulation and exercise performance by redistributing blood flow to aid heat loss and/or muscle function. This study assessed 7 days L-citrulline supplementation on running performance in the heat, whilst mildly hypohydrated.Methods13 endurance runners (2 female, 31 8 y, V. mathop { text{V}} limits {.} O2peak 60 6 mL/kg/min) participated in a randomised crossover study with 7 days L-citrulline (CIT 6 g/d) or placebo (maltodextrin powder PLA) supplementation. Participants completed a 50 min running preload at 65 V. mathop { text{V}} limits {.} O2peak (32 C, 50 relative humidity) to induce hyperthermia and hypohydration before a 3 km running time trial (TT). Body mass and blood samples were collected at baseline, pre-preload, post-preload and post-TT, whilst core and skin temperature, heart rate and perceptual responses were collected periodically throughout.ResultsTT performance was not different between trials (CIT 865 142 s PLA 892 154 s P 0.437). Core and skin temperature and heart rate (P 0.270), hydration (sweat rate, plasma volume, osmolality) indices (P 0.216), GI damage (P 0.260) and perceptual responses (P 0.610) were not different between trials during the preload and TT.Conclusions7 days of L-citrulline supplementation had no effect on 3 km running performance in the heat or any effects on thermoregulation or GI damage in trained runners in a hypohydrated state

Family Physicians’ Attitudes and Practices Regarding Assessments of Medical Fitness to Drive in Older Persons

BACKGROUND: Higher crash rates per mile driven in older drivers have focused attention on the assessment of older drivers. OBJECTIVE: To examine the attitudes and practices of family physicians regarding fitness-to-drive issues in older persons. DESIGN: Survey questionnaire. PARTICIPANTS: The questionnaire was sent to 1,000 randomly selected Canadian family physicians. Four hundred sixty eligible physicians returned completed questionnaires. MEASUREMENTS: Self-reported attitudes and practices towards driving assessments and the reporting of medically unsafe drivers. RESULTS: Over 45% of physicians are not confident in assessing driving fitness and do not consider themselves to be the most qualified professionals to do so. The majority (88.6%) feel that they would benefit from further education in this area. About 75% feel that reporting a patient as an unsafe driver places them in a conflict of interest and negatively impacts on the patient and the physician–patient relationship. Nevertheless, most (72.4%) agree that physicians should be legally responsible for reporting unsafe drivers to the licensing authorities. Physicians from provinces with mandatory versus discretionary reporting requirements are more likely to report unsafe drivers (odds ratio [OR], 2.78; 95% confidence interval [CI], 1.58 to 4.91), but less likely to perform driving assessments (OR, 0.58; 95% CI, 0.39 to 0.85). Most driving assessments take between 10 and 30 minutes, with much variability in the components included. CONCLUSIONS: Family physicians lack confidence in performing driving assessments and note many negative consequences of reporting unsafe drivers. Education about assessing driving fitness and approaches that protect the physician–patient relationship when reporting occurs are needed