Publications
161 results found
Jones H, Bailey TG, Barr DA, et al., 2019, Is core temperature the trigger of a menopausal hot flush?, Menopause, Vol: 26, Pages: 1016-1023
OBJECTIVE: Menopausal hot flushes negatively impact quality of life and may be a biomarker of cardiovascular and metabolic disease risk; therefore understanding the physiology of hot flushes is important. Current thinking is that a small elevation (∼0.03-0.05C) in core temperature surpasses a sweating threshold (that is reduced in the menopause), sweating is activated, and a hot flush ensues. Nevertheless, more recent studies examining thermoregulatory control question whether core temperature per se can explain the trigger for a hot flush. The primary aim of this study was to assess the contribution of increases in core temperature on the occurrence of menopausal hot flushes. METHODS: For this purpose, 108 hot flushes were objectively assessed in a laboratory setting in 72 symptomatic postmenopausal women (aged 45.8 ± 5.1 years; body mass index 25.9 ± 4.5 kg/m) from five previously reported studies. Women rested, wearing a tube-lined suit (or trousers), which was perfused with 34C water. A subset then underwent mild heat stress (48°C water). Sweat rate, skin blood flow, blood pressure, heart rate, skin, and core temperature were measured continuously throughout. A hot flush was objectively identified during rest (spontaneous hot flush) or mild heating as an abrupt increase in sternal sweat rate. Further, a subset of symptomatic postmenopausal women (n = 22) underwent whole-body passive heating for 60 minutes to identify core temperature thresholds and sensitivities for sweat rate and cutaneous vasodilation, which were compared to a subset of premenopausal women (n = 18). Data were analyzed using t tests and/or general linear modeling, and are presented as mean (95% confidence interval). RESULTS: In the 20 minutes before a spontaneous hot flush, core temperature increased by 0.03 ± 0.12C (P < 0.05), but only 51% of hot flushes were preceded by an increase in core temperature. During mild heating, 76% of hot flushes were preceded by an
Hesketh K, Shepherd SO, Strauss JA, et al., 2019, Passive heat therapy in sedentary humans increases skeletal muscle capillarization and eNOS content but not mitochondrial density or GLUT4 content, AMERICAN JOURNAL OF PHYSIOLOGY-HEART AND CIRCULATORY PHYSIOLOGY, Vol: 317, Pages: H114-H123, ISSN: 0363-6135
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- Citations: 39
Mullington CJ, Low DA, Strutton PH, et al., 2018, Body temperature, cutaneous heat loss and skin blood flow during epidural anaesthesia for emergency caesarean section, Anaesthesia, Vol: 73, Pages: 1500-1506, ISSN: 0003-2409
It is not clear how converting epidural analgesia for labour to epidural anaesthesia for emergency caesarean section affects either cutaneous vasomotor tone or mean body temperature. We hypothesised that topping up a labour epidural blocks active cutaneous vasodilation (cutaneous heat loss and skin blood flow decrease), and that as a result mean body temperature increases. Twenty women in established labour had body temperature, cutaneous heat loss and skin blood flow recorded before and after epidural top‐up for emergency caesarean section. Changes over time were analysed with repeated measures ANOVA. Mean (SD) mean body temperature was 36.8 (0.5)°C at epidural top‐up and 36.9 (0.6)°C at delivery. Between epidural top‐up and delivery, the mean (SD) rate of increase in mean body temperature was 0.5 (0.5) °C.h−1. Following epidural top‐up, chest (p < 0.001) and forearm (p = 0.004) heat loss decreased, but head (p = 0.05), thigh (p = 0.79) and calf (p = 1.00) heat loss did not change. The mean (SD) decrease in heat loss was 15 (19) % (p < 0.001). Neither arm (p = 0.06) nor thigh (p = 0.10) skin blood flow changed following epidural top‐up. Despite the lack of change in skin blood flow, the most plausible explanation for the reduction in heat loss and the increase in mean body temperature is blockade of active cutaneous vasodilation. It is possible that a similar mechanism is responsible for the hyperthermia associated with labour epidural analgesia.
Miyasato RS, Silva-Batista C, Peçanha T, et al., 2018, Cardiovascular Responses During Resistance Exercise in Patients With Parkinson Disease., PM R, Vol: 10, Pages: 1145-1152
BACKGROUND: Patients with Parkinson disease (PD) present cardiovascular autonomic dysfunction that impairs blood pressure control. However, cardiovascular responses during resistance exercise are unknown in these patients. OBJECTIVE: To investigate cardiovascular responses during resistance exercise performed with different muscle masses in patients with PD. DESIGN: Prospective, repeated-measures. SETTING: Exercise Hemodynamic Laboratory, School of Physical Education and Sport, University of São Paulo. PARTICIPANTS: Thirteen patients with PD (4 women, 62.7 ± 1.3 years, stages 2-3 of the modified Hoehn and Yahr scale; "on" state of medication) and 13 paired control patients without PD (7 women, 66.2 ± 2.0 years). INTERVENTIONS: Both groups performed, in a random order, bilateral and unilateral knee extension exercises (2 sets, 10-12 maximal repetition, 2-minute intervals). MAIN OUTCOME MEASUREMENTS: Systolic blood pressure (SBP) and heart rate (HR) were assessed before (pre) and during the exercises. RESULTS: Independent of set and exercise type, SBP and HR increases were significantly lower in PD than the control group (combined values: +45 ± 2 versus +73 ± 4 mm Hg and +18 ± 1 versus +31 ± 2 bpm, P = .003 and .007, respectively). Independently of group and set, the SBP increase was greater in the bilateral than the unilateral exercise (combined values: +63 ± 4 versus +54 ± 3 mm Hg, P = .002), whereas the HR increase was similar. In addition, independently of group and exercise type, the SBP increase was greater in the second than the first set (combined values: +56 ± 4 versus +61 ± 4 mm Hg, P = .04), whereas the HR increases were similar. CONCLUSIONS: Patients with PD present attenuated increases in SBP and HR during resistance exercise in comparison with healthy subjects. These results support that resistance exercise is safe and well tolerated for patients with PD from a cardiov
Barton TJ, Low DA, Janssen TWJ, et al., 2018, Femoral Artery Blood Flow and Microcirculatory Perfusion During Acute, Low-Level Functional Electrical Stimulation in Spinal Cord Injury., Am J Phys Med Rehabil, Vol: 97, Pages: 721-726
OBJECTIVE: Functional electrical stimulation (FES) may help to reduce the risk of developing macrovascular and microvascular complications in people with spinal cord injury. Low-intensity FES has significant clinical potential because this can be applied continuously throughout the day. This study examines the acute effects of low-intensity FES using wearable clothing garment on vascular blood flow and oxygen consumption in people with spinal cord injury. DESIGN: This was a cross-sectional observation study. METHODS: Eight participants with a motor complete spinal cord injury received four 3-min unilateral FES to the gluteal and hamstring muscles. Skin and deep femoral artery blood flow and oxygen consumption were measured at baseline and during each bout of stimulation. RESULTS: Femoral artery blood flow increased by 18.1% with the application of FES (P = 0.02). Moreover, femoral artery blood flow increased further during each subsequent block of FES (P = 0.004). Skin perfusion did not change during an individual block of stimulation (P = 0.66). Skin perfusion progressively increased with each subsequent bout (P < 0.001). There was no change in femoral or skin perfusion across time in the nonstimulated leg (all P > 0.05). CONCLUSION: Low-intensity FES acutely increased blood flow during stimulation, with a progressive increase across subsequent FES bouts. These observations suggest that continuous, low-intensity FES may represent a practical and effective strategy to improve perfusion and reduce the risk of vascular complications.
Owens AP, Low DA, Critchley HD, et al., 2018, Emotional orienting during interoceptive threat in orthostatic intolerance: Dysautonomic contributions to psychological symptomatology in the postural tachycardia syndrome and vasovagal syncope., Auton Neurosci, Vol: 212, Pages: 42-47
Cognitive and emotional processes are influenced by interoception (homeostatic somatic feedback), particularly when physiological arousal is unexpected and discrepancies between predicted and experienced interoceptive signals may engender anxiety. Due to the vulnerability for comorbid psychological symptoms in forms of orthostatic intolerance (OI), this study investigated psychophysiological contributions to emotional symptomatology in 20 healthy control participants (13 females, mean age 36 ± 8 years), 20 postural tachycardia syndrome (PoTS) patients (18 females, mean age 38 ± 13 years) and 20 vasovagal syncope (VVS) patients (15 females, mean age 39 ± 12 years). We investigated indices of emotional orienting responses (OR) to randomly presented neutral, pleasant and unpleasant images in the supine position and during the induced interoceptive threat of symptom provocation of head-up tilt (HUT). PoTS and VVS patients produced greater indices of emotional responsivity to unpleasant images and, to a lesser degree, pleasant images, during interoceptive threat. Our findings are consistent with biased deployment of response-focused emotion regulation (ER) while patients are symptomatic, providing a mechanistic underpinning of how pathological autonomic overexcitation predisposes to anxiogenic traits in PoTS and VVS patients. This hypothesis may improve our understanding of why orthostasis exacerbates cognitive symptoms despite apparently normal cerebral autoregulation, and offer novel therapeutic targets for behavioural interventions aimed at reducing comorbid cognitive-affective symptoms in PoTS and VVS.
Atkinson CL, Carter HH, Thijssen DHJ, et al., 2018, Localised cutaneous microvascular adaptation to exercise training in humans., Eur J Appl Physiol, Vol: 118, Pages: 837-845
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 14 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 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.
Owens AP, Friston KJ, Low DA, et al., 2018, Investigating the relationship between cardiac interoception and autonomic cardiac control using a predictive coding framework., Auton Neurosci, Vol: 210, Pages: 65-71
Predictive coding models, such as the 'free-energy principle' (FEP), have recently been discussed in relation to how interoceptive (afferent visceral feedback) signals update predictions about the state of the body, thereby driving autonomic mediation of homeostasis. This study appealed to 'interoceptive inference', under the FEP, to seek new insights into autonomic (dys)function and brain-body integration by examining the relationship between cardiac interoception and autonomic cardiac control in healthy controls and patients with forms of orthostatic intolerance (OI); to (i) seek empirical support for interoceptive inference and (ii) delineate if this relationship was sensitive to increased interoceptive prediction error in OI patients during head-up tilt (HUT)/symptom provocation. Measures of interoception and heart rate variability (HRV) were recorded whilst supine and during HUT in healthy controls (N = 20), postural tachycardia syndrome (PoTS, N = 20) and vasovagal syncope (VVS, N = 20) patients. Compared to controls, interoceptive accuracy was reduced in both OI groups. Healthy controls' interoceptive sensibility positively correlated with HRV whilst supine. Conversely, both OI groups' interoceptive awareness negatively correlated with HRV during HUT. Our pilot study offers initial support for interoceptive inference and suggests OI cohorts share a central pathophysiology underlying interoceptive deficits expressed across distinct cardiovascular autonomic pathophysiology. From a predictive coding perspective, OI patients' data indicates a failure to attenuate/modulate ascending interoceptive prediction errors, reinforced by the concomitant failure to engage autonomic reflexes during HUT. Our findings offer a potential framework for conceptualising how the human nervous system maintains homeostasis and how both central and autonomic processes are ultimately implicated in dysautonomia.
Woodward KA, Hopkins ND, Draijer R, et al., 2018, Acute black tea consumption improves cutaneous vascular function in healthy middle-aged humans, CLINICAL NUTRITION, Vol: 37, Pages: 242-249, ISSN: 0261-5614
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- Citations: 10
Pecanha T, Forjaz CLM, Low DA, 2017, Additive effects of heating and exercise on baroreflex control of heart rate in healthy males, JOURNAL OF APPLIED PHYSIOLOGY, Vol: 123, Pages: 1555-1562, ISSN: 8750-7587
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- Citations: 8
Roberts KA, van Gent T, Hopkins ND, et al., 2017, Reproducibility of four frequently used local heating protocols to assess cutaneous microvascular function., Microvasc Res, Vol: 112, Pages: 65-71
BACKGROUND: Skin microvascular responses to local heating are frequently used to assess microvascular function. Several local heating protocols have been developed, all varying slightly in execution. The aim of this study was to determine the inter-day reproducibility of the four most commonly used local heating protocols in healthy young subjects. METHODS: Fifteen, healthy males (28±5yrs, BMI 25±2kg/m2) attended two experimental trials 2-7days apart. During each trial, baseline and maximal thermally stimulated forearm skin responses were examined simultaneously at four sites on the dominant forearm using laser Doppler flowmetry (LDF). The following heating protocols were adopted: 1. Rapid 39°C (0.5°C/5s), 2. Rapid 42°C (0.5°C/5s) 3. Gradual 42°C (0.5°C/2min 30s) and 4. Slow 42°C (0.5°C/5min). The coefficient of variation (CV) was calculated for absolute flux, cutaneous vascular conductance (CVC; flux/mean arterial pressure, MAP) and CVC expressed as a percentage of maximal CVC at 44°C (%CVCmax) at three different time points; baseline (33°C), plateau (39/42°C) and maximal (44°C). RESULTS: Reproducibility of baseline flux, CVC and %CVCmax was 17-29% across all protocols. During the plateau, Rapid, Gradual and Slow 42°C demonstrated a reproducibility of 13-18% for flux and CVC and 5-11% for %CVCmax. However, Rapid 39°C demonstrated a lower reproducibility for flux, CVC and %CVCmax (all 21%). Reproducibility at 44°C was 12-15% for flux and CVC across all protocols. CONCLUSION: This is the first study examining inter-day reproducibility across four local heating protocols. The good-to-moderate reproducibility of the Rapid, Gradual and Slow 42°C protocols support their (simultaneous) use to assess microvascular function. Using Rapid 39°C may require a greater number of subjects to detect differences within subjects.
Mawhinney C, Low DA, Jones H, et al., 2017, Cold Water Mediates Greater Reductions in Limb Blood Flow than Whole Body Cryotherapy., Med Sci Sports Exerc, Vol: 49, Pages: 1252-1260
PURPOSE: Cold-water immersion (CWI) and whole body cryotherapy (WBC) are widely used recovery methods in an attempt to limit exercise-induced muscle damage, soreness, and functional deficits after strenuous exercise. The aim of this study was to compare the effects of ecologically valid CWI and WBC protocols on postexercise lower limb thermoregulatory, femoral artery, and cutaneous blood flow responses. METHODS: Ten males completed a continuous cycle exercise protocol at 70% maximal oxygen uptake until a rectal temperature of 38°C was attained. Participants were then exposed to lower-body CWI (8°C) for 10 min, or WBC (-110°C) for 2 min, in a randomized crossover design. Rectal and thigh skin, deep, and superficial muscle temperatures, thigh, and calf skin blood flow (laser Doppler flowmetry), superficial femoral artery blood flow (duplex ultrasound), and arterial blood pressure were measured before, and for 40 min post, cooling interventions. RESULTS: Greater reductions in thigh skin (CWI, -5.9°C ± 1.8°C; WBC, 0.2°C ± 0.5°C; P < 0.001) and superficial (CWI, -4.4°C ± 1.3°C; WBC, -1.8°C ± 1.1°C; P < 0.001) and deep (CWI, -2.9°C ± 0.8°C; WBC, -1.3°C ± 0.6°C; P < 0.001) muscle temperatures occurred immediately after CWI. Decreases in femoral artery conductance were greater after CWI (CWI, -84% ± 11%; WBC, -59% ± 21%, P < 0.02) and thigh (CWI, -80% ± 5%; WBC, -59% ± 14%, P < 0.001), and calf (CWI, -73% ± 13%; WBC, -45% ± 17%, P < 0.001) cutaneous vasoconstriction was greater after CWI. Reductions in rectal temperature were similar between conditions after cooling (CWI, -0.6°C ± 0.4°C; WBC, -0.6°C ± 0.3°C; P = 0.98). CONCLUSION: Greater reductions in blood flow and tissue temperature were observed after CWI in comparison with WBC. These novel findings have practical and clinical impl
Mawhinney C, Jones H, Low DA, et al., 2017, Influence of cold-water immersion on limb blood flow after resistance exercise., Eur J Sport Sci, Vol: 17, Pages: 519-529
This study determined the influence of cold (8°C) and cool (22°C) water immersion on lower limb and cutaneous blood flow following resistance exercise. Twelve males completed 4 sets of 10-repetition maximum squat exercise and were then immersed, semi-reclined, into 8°C or 22°C water for 10-min, or rested in a seated position (control) in a randomized order on different days. Rectal and thigh skin temperature, muscle temperature, thigh and calf skin blood flow and superficial femoral artery blood flow were measured before and after immersion. Indices of vascular conductance were calculated (flux and blood flow/mean arterial pressure). The colder water reduced thigh skin temperature and deep muscle temperature to the greatest extent (P < .001). Reductions in rectal temperature were similar (0.2-0.4°C) in all three trials (P = .69). Femoral artery conductance was similar after immersion in both cooling conditions, with both conditions significantly lower (55%) than the control post-immersion (P < .01). Similarly, there was greater thigh and calf cutaneous vasoconstriction (40-50%) after immersion in both cooling conditions, relative to the control (P < .01), with no difference between cooling conditions. These findings suggest that cold and cool water similarly reduce femoral artery and cutaneous blood flow responses but not muscle temperature following resistance exercise.
Owens AP, Low DA, Iodice V, et al., 2017, The genesis and presentation of anxiety in disorders of autonomic overexcitation, AUTONOMIC NEUROSCIENCE-BASIC & CLINICAL, Vol: 203, Pages: 81-87, ISSN: 1566-0702
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- Citations: 22
Bailey TG, Cable T, Aziz N, et al., 2017, In Reply., Menopause, Vol: 24, Pages: 118-120
Vichayanrat E, Low DA, Iodice V, et al., 2017, Twenty-four-hour ambulatory blood pressure and heart rate profiles in diagnosing orthostatic hypotension in Parkinson's disease and multiple system atrophy, EUROPEAN JOURNAL OF NEUROLOGY, Vol: 24, Pages: 90-97, ISSN: 1351-5101
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- Citations: 22
Peçanha T, Forjaz CLDM, Low DA, 2017, Passive Heating Attenuates Post-exercise Cardiac Autonomic Recovery in Healthy Young Males., Front Neurosci, Vol: 11, ISSN: 1662-4548
Post-exercise heart rate (HR) recovery (HRR) presents a biphasic pattern, which is mediated by parasympathetic reactivation and sympathetic withdrawal. Several mechanisms regulate these post-exercise autonomic responses and thermoregulation has been proposed to play an important role. The aim of this study was to test the effects of heat stress on HRR and HR variability (HRV) after aerobic exercise in healthy subjects. Twelve healthy males (25 ± 1 years, 23.8 ± 0.5 kg/m2) performed 14 min of moderate-intensity cycling exercise (40-60% HRreserve) followed by 5 min of loadless active recovery in two conditions: heat stress (HS) and normothermia (NT). In HS, subjects dressed in a whole-body water-perfused tube-lined suit to increase internal temperature (Tc) by ~1°C. In NT, subjects did not wear the suit. HR, core and skin temperatures (Tc and Tsk), mean arterial pressure (MAP) skin blood flow (SKBF), and cutaneous vascular conductance (CVC) were measured throughout and analyzed during post-exercise recovery. HRR was assessed through calculations of HR decay after 60 and 300 s of recovery (HRR60s and HRR300s), and the short- and long-term time constants of HRR (T30 and HRRt). Post-exercise HRV was examined via calculations of RMSSD (root mean square of successive RR intervals) and RMS (root mean square residual of RR intervals). The HS protocol promoted significant thermal stress and hemodynamic adjustments during the recovery (HS-NT differences: Tc = +0.7 ± 0.3°C; Tsk = +3.2 ± 1.5°C; MAP = -12 ± 14 mmHg; SKBF = +90 ± 80 a.u; CVC = +1.5 ± 1.3 a.u./mmHg). HRR and post-exercise HRV were significantly delayed in HS (e.g., HRR60s = 27 ± 9 vs. 44 ± 12 bpm, P < 0.01; HRR300s = 39 ± 12 vs. 59 ± 16 bpm, P < 0.01). The effects of heat stress (e.g., the HS-NT differences) on HRR were associated with its effects on thermal and hemodynamic responses. In conclusion, heat stress delays HRR
Bailey TG, Cable NT, Miller GD, et al., 2016, Repeated Warm Water Immersion Induces Similar Cerebrovascular Adaptations to 8 Weeks of Moderate-Intensity Exercise Training in Females., Int J Sports Med, Vol: 37, Pages: 757-765
Exercise training has the potential to enhance cerebrovascular function. Warm water immersion has recently been shown to enhance vascular function including the cerebrovascular response to heating. We suggest that passive heating can be used alternatively to exercise. Our aim was to compare the effects of exercise with warm-water immersion training on cerebrovascular and thermoregulatory function. 18 females (25±5 y) performed 8 weeks of cycling (70% HRmax) or warm water immersion (42°C) for 30 min 3 times per week. Brachial artery flow-mediated dilation (FMD) and peak cardiorespiratory fitness (VO2peak) were measured prior to and following both interventions. A passive heat stress was employed to obtain temperature thresholds (Tb) and sensitivities for sweat rate (SR) and cutaneous vasodilation (CVC). Middle cerebral artery velocity (MCAv) was measured throughout. FMD and VO2peak improved following both interventions (p<0.05). MCAv and cerebrovascular conductance were higher at rest and during passive heating (p<0.001 and <0.001, respectively) following both interventions. SR occurred at a lower Tb following both interventions and SR sensitivity also increased, with a larger increase at the chest (p<0.001) following water immersion. CVC occurred at a lower Tb (p<0.001) following both interventions. Warm water immersion elicits similar cerebrovascular, conduit, and thermoregulatory adaptations compared to a period of moderate-intensity exercise training.
Low DA, Bailey TG, Cable NT, et al., 2016, Thermoregulatory responses to combined moderate heat stress and hypoxia, Microcirculation, Vol: 23, Pages: 487-494, ISSN: 1549-8719
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. This article is protected by copyright. All rights reserved.
Bailey TG, Cable NT, Aziz N, et al., 2016, Exercise training reduces the frequency of menopausal hot flushes by improving thermoregulatory control, Menopause, Vol: 23, ISSN: 1072-3714
OBJECTIVE: Postmenopausal hot flushes occur due to a reduction in estrogen 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 women 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) were measured during passive heating. Women 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/min [95% CI: 1.87, 8.16]; P = 0.04) and reduced hot flush frequency (48 hot flushes/wk [39, 56]; P < 0.001) after exercise compared with 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, 5.2]; P = 0.04) compared with control. Sweat rate and skin blood flow thresholds occurred approximately 0.19°C 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 after exercise compared with 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.
Owens AP, Low DA, Iodice V, et al., 2016, Emotion and the autonomic nervous system-a two-way street: Insights from affective, autonomic and dissociative disorders, The Curated Reference Collection in Neuroscience and Biobehavioral Psychology, ISBN: 9780128093245
Brain and body are coupled by the autonomic nervous system. Emotions evoke “top-down” autonomic responses and are shaped by “bottom-up” afferent somatic feedback. This psychophysiological integration is supported by shared autonomic and emotional neuroanatomical pathways. Emotional stress disrupts normative autonomic function, typically through sympathoexcitation. Conversely, in dissociative disorders, emotional stress may suppress sympathoexcitation despite subjective emotional distress. Psychophysiological decoupling is further observed in forms of dysautonomia defined by autonomic overexcitation, resulting in emotional symptoms via interoception of dysautonomic symptoms. The study of these disorders elucidates mechanisms of psychophysiological integration and improves our pathophysiological understanding of affective, autonomic and dissociative disorders.
Bailey TG, Cable NT, Aziz N, et al., 2015, Exercise training reduces the acute physiological severity of post-menopausal hot flushes, Journal of Physiology - London, Vol: 594, Pages: 657-667, ISSN: 0022-3751
KEY POINTS: A post-menopausal hot flush consists of profuse physiological elevations in cutaneous vasodilatation and sweating that are accompanied by reduced brain blood flow. These responses can be used to objectively quantify hot flush severity. The impact of an exercise training intervention on the physiological responses occurring during a hot flush is currently unknown. In a preference-controlled trial involving 21 post-menopausal women, 16 weeks of supervised moderate intensity exercise training was found to improve cardiorespiratory fitness and attenuate cutaneous vasodilatation, sweating and the reductions in cerebral blood flow during a hot flush. It is concluded that the improvements in fitness that are mediated by 16 weeks of exercise training reduce the severity of physiological symptoms that occur during a post-menopausal hot flush. ABSTRACT: A hot flush is characterised by feelings of intense heat, profuse elevations in cutaneous vasodilatation and sweating, and reduced brain blood flow. Exercise training reduces self-reported hot flush severity, but underpinning physiological data are lacking. We hypothesised that exercise training attenuates the changes in cutaneous vasodilatation, sweat rate and cerebral blood flow during a hot flush. In a preference trial, 18 symptomatic post-menopausal women underwent a passive heat stress to induce hot flushes at baseline and follow-up. Fourteen participants opted for a 16 week moderate intensity supervised exercise intervention, while seven participants opted for control. Sweat rate, cutaneous vasodilatation, blood pressure, heart rate and middle cerebral artery velocity (MCAv) were measured during the hot flushes. Data were binned into eight equal segments, each representing 12.5% of hot flush duration. Weekly self-reported frequency and severity of hot flushes were also recorded at baseline and follow-up. Following training, mean hot flush sweat rate decreased by 0.04 mg cm(2) min(-1) at the chest (95% confide
Idiaquez J, Farias H, Torres F, et al., 2015, Autonomic symptoms in hypertensive patients with post-acute minor ischemic stroke, CLINICAL NEUROLOGY AND NEUROSURGERY, Vol: 139, Pages: 188-191, ISSN: 0303-8467
BackgroundMost studies regarding autonomic dysfunction in ischemic stroke are limited to heart rate and blood pressure changes during the acute phase. However, there are few data on quantitative assessment of autonomic symptoms. We sought to assess autonomic symptoms in hypertensive ischemic stroke patients.MethodsIn 100 hypertensive patients (45 with symptomatic ischemic stroke (6 months after stroke onset) and 55 without stroke), we assessed autonomic symptoms using the Scale for Outcomes in Parkinson disease-Autonomic (SCOPA-AUT).ResultsThe age (mean ± standard deviation) for the stroke group was 66 ± 12 and 63 ± 15 for the without stroke group (P = 0.8). Orthostatic hypotension occurred in 3.6% of the stroke group and 4.4% in the group without stroke. The total SCOPA-AUT score was higher in the stroke group compared with the group without stroke (P = 0.001). Domain scores for gastrointestinal (P = 0.001), urinary (P = 0.005) and cardiovascular (P = 0.001) were higher in the stroke group. No differences were found when comparing the total SCOPA-AUT scores for stroke subtypes (P = 0.168) and for lateralization (P = 0.6). SCOPA AUT scores were correlated with depression scores (P = 0.001) but not with stroke severity (P = 0.2).ConclusionAutonomic symptoms, especially, gastrointestinal, urinary and cardiovascular function, were significantly increased in hypertensive patients with minor ischemic stroke. Symptoms were associated with depression but not with the characteristic of the stroke.
Wingo JE, Low DA, Keller DM, et al., 2015, Combined facial heating and inhalation of hot air do not alter thermoeffector responses in humans, American Journal of Physiology - Regulatory Integrative and Comparative Physiology, Vol: 309, Pages: R623-R627, ISSN: 0363-6119
The influence of thermoreceptors in human facial skin on thermoeffector responses is equivocal; furthermore, the presence of thermoreceptors in the respiratory tract and their involvement in thermal homeostasis has not been elucidated. This study tested the hypothesis that hot air directed on the face and inhaled during whole body passive heat stress elicits an earlier onset and greater sensitivity of cutaneous vasodilation and sweating than that directed on an equal skin surface area away from the face. Six men and two women completed two trials separated by ∼1 wk. Participants were passively heated (water-perfused suit; core temperature increase ∼0.9°C) while hot air was directed on either the face or on the lower leg (counterbalanced). Skin blood flux (laser-Doppler flowmetry) and local sweat rate (capacitance hygrometry) were measured at the chest and one forearm. During hot-air heating, local temperatures of the cheek and leg were 38.4 ± 0.8°C and 38.8 ± 0.6°C, respectively (P = 0.18). Breathing hot air combined with facial heating did not affect mean body temperature onsets (P = 0.97 and 0.27 for arm and chest sites, respectively) or slopes of cutaneous vasodilation (P = 0.49 and 0.43 for arm and chest sites, respectively), or the onsets (P = 0.89 and 0.94 for arm and chest sites, respectively), or slopes of sweating (P = 0.48 and 0.65 for arm and chest sites, respectively). Based on these findings, respiratory tract thermoreceptors, if present in humans, and selective facial skin heating do not modulate thermoeffector responses during passive heat stress.
Dawson EA, Low DA, Meeuwis IH, et al., 2015, Reproducibility of cutaneous vascular conductance responses to slow local heating assessed using seven-laser array probes, Microcirculation, Vol: 22, Pages: 276-284, ISSN: 1549-8719
OBJECTIVE: Gradual local heating of the skin induces a largely NO-mediated vasodilatation. However, use of this assessment of microvascular health is limited because little is known about its reproducibility. METHODS: Healthy volunteers (n = 9) reported twice to the laboratory. CVC, derived from laser Doppler flux and mean arterial pressure, was examined in response to a standardized local heating protocol (0.5°C per 150 second from 33°C to 42°C, followed by 20 minutes at 44°C). Skin responses were examined at two locations on the forearm (between-site). Heating was repeated after a break of 24-72 hours (between-day). Reproducibility of skin responses at 33-42°C is presented for absolute CVC and relative CVC responses corrected for maximal CVC at 44°C (%CVCmax ). RESULTS: Between-day reproducibility of baseline CVC and %CVCmax for both sites was relatively poor (22-30%). At 42°C, CVC and %CVCmax responses showed less variation (9-19%), whilst absolute CVC responses at 44°C were 14-17%. Between-day variation for %CVCmax increased when using data from site 1 on day 1, but site 2 on the subsequent day (25%). CONCLUSION: Day-to-day reproducibility of baseline laser Doppler-derived skin perfusion responses is poor, but acceptable when absolute and relative skin perfusion to a local gradual heating protocol is utilized and site-to-site variation is minimized.
Owens AP, David AS, Low DA, et al., 2015, Abnormal cardiovascular sympathetic and parasympathetic responses to physical and emotional stimuli in depersonalization disorder, Frontiers in Neuroscience, Vol: 9, ISSN: 1662-4548
Stuebner E, Vichayanrat E, Low DA, et al., 2015, Non-dipping nocturnal blood pressure and psychosis parameters in Parkinson disease, Clinical Autonomic Research, Vol: 25, Pages: 109-116, ISSN: 1619-1560
BackgroundNon-motor symptoms are increasingly recognized in Parkinson disease (PD) and include physical as well as psychological symptoms. A psychological condition that has been well studied in PD is psychosis. Cardiovascular autonomic dysfunction in PD can include a reversed or loss of blood pressure (BP) circadian rhythm, referred to as nocturnal non-dipping. The aim of this study was to determine the relationship between 24 h ambulatory blood pressure measurements (ABPM), i.e., absence or presence of nocturnal dipping, and psychosis scores in PD.MethodsTwenty-one patiens with PD underwent 24 h ABPM using an autonomic protocol. A decrease in nocturnal mean arterial blood pressure of less than 10 % was defined as non-dipping. Patients were interviewed (including the brief psychiatric rating scale; BPRS) for the assessment of psychosis.ResultsEleven patients were dippers and 10 were non-dippers. BPRS scores were higher in non-dippers, who, on average, met the criteria for psychosis (mean non-dipper BPRS: 34.3 ± 7.3 vs mean dipper BPRS: 27.5 ± 5.3; cutoff for “mildly ill” 31). There was a correlation between BPRS scores and non-dipping, indicating that those patients who had a blunted nocturnal fall in BP were more prone to psychotic symptoms (Pearson’s Correlation = 0.554, p = 0.009).ConclusionThese results suggest that, among PD patients, a non-dipping circadian rhythm is associated with more severe symptoms of psychosis than is a dipping circadian rhythm. This association warrants further investigation.
Low DA, Vichayanrat E, Iodice V, et al., 2014, Exercise hemodynamics in Parkinson's disease and autonomic dysfunction, PARKINSONISM & RELATED DISORDERS, Vol: 20, Pages: 549-553, ISSN: 1353-8020
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Vichayanrat E, Low DA, Stuebner E, et al., 2014, The usefulness of 24 h ambulatory blood pressure and heart rate monitoring (24 h-ABPM) in diagnosing orthostatic hypotension (OH) in patients with parkinsonian disorders, Joint Congress of European Neurology, Publisher: SPRINGER HEIDELBERG, Pages: S63-S63, ISSN: 0340-5354
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