The Production of Space: The Meaning of Place

Abstract for paper presentation: This paper explores the relationship between the production of space and the meaning of place through the artwork 'In Passing'- a moving image and text based sound work. The geographical context for 'In Passing' is a culturally neglected and 'unplanned' settlement which sits on an unstable shingle coastline bordering Romney Marsh in the South East of England. The work is informed by fieldwork methods of gathering information about a local landscape and a consideration of the relationship between chronological movement and psychic duration in the artwork (Bergson). The paper discusses the geological terrain and social and industrial development of the landscape, how fieldwork methods of gathering information about a local landscape can be assembled to explore the 'quotidien' , and how this shifting coastal terrain can be experienced as flow, counterflow and infinite variation through the form of the artwork. The artwork and the paper suggest two things: 1. That we can understand the meaning of place through a fieldwork activity of walking and close observation, which then is transformed into a space/time synthesis understood through visual and oral inscription. 2.That we can use the artistic production of space and duration to draw attention to neglected, overlooked pockets of land, explore marginal existences, processes of flux and discover variegation in apparent uniformity. 'In Passing' description of artwork: The video draws a linear trajectory through the landscape from a moving vehicle (a local miniature train). The locked camera positioned low to the ground, records a visual track which reveals a 'behind the scenes' view of vernacular architecture, 'waste' land and suburban gardens which are mixed up with features of agricultural, industrial and touristic occupation. Accompanying this track, recorded voices rhythmically recite the names of classes of things particular to this landscape (species of local flora; leptidoptera; house names and models of vehicles) collected through observational walking in the landscape. The sound track as a textured ribbon of voices in parallel with the visual track results in images and signs that emerge in relation to one another, sedimented and intersecting. The resulting artwork is a particular map of place at a particular time in space, a synthetic fabrication of constantly shifting relations which aims to enrich our understanding of the lived landscape, however mundane, insignificant and despoiled it may appear to the casual eye. 'In Passing' can be shown as video projection or on a flat screen- both with speakers. The complete work extends for 75 mins on a loop. It is not meant to be experienced in cinematic 'sit down' format, but rather to be encountered as the title suggests, 'In passing'. Therefore the viewer can spend as long as they like with the work before moving on

Circulatory limitations to exercise capacity in humans: the impact of heat stress and dehydration on brain and muscle blood flow and metabolism

This thesis was submitted for the award of Doctor of Philosophy and was awarded by Brunel University LondonHeat stress and dehydration pose a severe challenge to physiological function and the capability to perform physical work. There is, however, limited knowledge on the regional haemodynamic and metabolic responses to strenuous exercise in environmentally stressful conditions. The primary aim of this thesis was to examine whether dehydration and heat stress compromise brain, muscle and systemic blood flow and metabolism, and whether depressed brain and muscle oxygen delivery underpin reduced exercise capacity during graded incremental and prolonged exercise. This thesis makes an original contribution to the knowledge by showing for the first time that dehydration markedly accelerates the decline in cerebral blood flow during maximal incremental (Chapter 4) and prolonged sub-maximal exercise (Chapter 5) in the heat. Cerebral metabolism, however, is preserved by compensatory increases in substrate extraction. Falling carbon dioxide tension underpinned the decline in CBF. However, a distinct regional distribution of blood flow across the head was observed, suggesting that different mechanisms are responsible for the regulation of regional blood flow within the head. A reduced cerebral metabolism is therefore an unlikely factor explaining the compromised exercise capacity in physiologically stressful hot environments. Rather, restrictions in active muscle blood flow and oxygen supply, which are not apparent during sub-maximal exercise, may explain the reduced maximal aerobic power in heat stressed conditions. For the first time we have manipulated skin and core temperature to show that combined internal and skin hyperthermia reduces maximal aerobic power in association with restrictions in limb, brain and systemic blood flow and skeletal muscle metabolism (Chapter 6). Overall, the findings of the present thesis provide novel information on how circulatory limitations across contracting skeletal muscle, brain and systemic tissues and organs might underpin the impairment in exercise capacity in physiologically taxing environments evoking significant dehydration and hyperthermia.Gatorade Sports Science Institute, PepsiCo Inc., US

Local temperature-sensitive mechanisms are important mediators of limb tissue hyperemia in the heat-stressed human at rest and during small muscle mass exercise.

Limb tissue and systemic blood flow increases with heat stress, but the underlying mechanisms remain poorly understood. Here, we tested the hypothesis that heat stress-induced increases in limb tissue perfusion are primarily mediated by local temperature-sensitive mechanisms. Leg and systemic temperatures and hemodynamics were measured at rest and during incremental single-legged knee extensor exercise in 15 males exposed to 1 h of either systemic passive heat-stress with simultaneous cooling of a single leg (n=8) or isolated leg heating or cooling (n=7). Systemic heat-stress increased core, skin and heated leg blood (Tb) temperatures, cardiac output and heated leg blood flow (LBF, 0.6 ± 0.1 l.min(-1); P0.05). Increased heated leg deep tissue BF was closely related to Tb (R(2) = 0.50; P0.05), despite unchanged systemic temperatures and hemodynamics. During incremental exercise, heated LBF was consistently maintained ~ 0.6 l.min(-1) higher than that in the cooled leg (P<0.01), with LBF and vascular conductance in both legs showing a strong correlation with their respective local Tb (R(2) = 0.85 and 0.95, P<0.05). We conclude that local temperature-sensitive mechanisms are important mediators in limb tissue perfusion regulation both at rest and during small-muscle mass exercise in hyperthermic humans.The invasive study was partially funded by Gatorade Sports Science Institute, PepsiCo

Whole-body heat stress and exercise stimulate the appearance of platelet microvesicles in plasma with limited influence of vascular shear stress

Intense, large muscle mass exercise increases circulating microvesicles, but our understanding of microvesicle dynamics and mechanisms inducing their release remains limited. However, increased vascular shear stress is generally thought to be involved. Here, we manipulated exercise-independent and exercise-dependent shear stress using systemic heat stress with localized single-leg cooling (low shear) followed by single-leg knee extensor exercise with the cooled or heated leg (Study 1, n = 8) and whole-body passive heat stress followed by cycling (Study 2, n = 8). We quantified femoral artery shear rates (SRs) and arterial and venous platelet microvesicles (PMV-CD41+) and endothelial microvesicles (EMV-CD62E+). In Study 1, mild passive heat stress while one leg remained cooled did not affect [microvesicle] (P ≥ 0.05). Single-leg knee extensor exercise increased active leg SRs by ~12-fold and increased arterial and venous [PMVs] by two- to threefold, even in the nonexercising contralateral leg (P < 0.05). In Study 2, moderate whole-body passive heat stress increased arterial [PMV] compared with baseline (mean±SE, from 19.9 ± 1.5 to 35.5 ± 5.4 PMV.μL-1.103, P < 0.05), and cycling with heat stress increased [PMV] further in the venous circulation (from 27.5 ± 2.2 at baseline to 57.5 ± 7.2 PMV.μL-1.103 during cycling with heat stress, P < 0.05), with a tendency for increased appearance of PMV across exercising limbs. Taken together, these findings demonstrate that whole-body heat stress may increase arterial [PMV], and intense exercise engaging either large or small muscle mass promote PMV formation locally and systemically, with no influence upon [EMV]. Local shear stress, however, does not appear to be the major stimulus modulating PMV formation in healthy humans

Dehydration accelerates reductions in cerebral blood flow during prolonged exercise in the heat without compromising brain metabolism

Dehydration hastens the decline in cerebral blood flow (CBF) during incremental exercise, while the cerebral metabolic rate for oxygen (CMRO2) is preserved. It remains unknown whether CMRO2 is also maintained during prolonged exercise in the heat and whether an eventual decline in CBF is coupled to fatigue. Two studies were undertaken. In study 1, ten male cyclists cycled in the heat for ~2 h with (control) and without fluid replacement (dehydration) while internal (ICA) and external (ECA) carotid artery blood flow and core and blood temperature were obtained. Arterial and internal jugular venous blood samples were assessed with dehydration to evaluate the CMRO2. In study 2 (8 males), middle cerebral artery blood velocity (MCA Vmean) was measured during prolonged exercise to exhaustion in both dehydrated and euhydrated states. After a rise at the onset of exercise, ICA flow declined to baseline with progressive dehydration (P < 0.05). However, cerebral metabolism remained stable through enhanced oxygen and glucose extraction (P < 0.05). ECA flow increased for one hour but declined prior to exhaustion. Fluid ingestion maintained cerebral and extra-cranial perfusion throughout non-fatiguing exercise. During exhaustive exercise, however, euhydration delayed but did not prevent the decline in cerebral perfusion. In conclusion, during prolonged exercise in the heat dehydration accelerates the decline in CBF without affecting CMRO2 and also restricts extra-cranial perfusion. Thus fatigue is related to reduction in CBF and extra-cranial perfusion rather than in CMRO2.The study was supported by a grant from the Gatorade Sports Science Institute, PepsiCo Inc, USA

Whole body hyperthermia, but not skin hyperthermia, accelerates brain and locomotor limb circulatory strain and impairs exercise capacity in humans

Cardiovascular strain and hyperthermia are thought to be important factors limiting exercise capacity in heat-stressed humans; however, the contribution of elevations in skin (Tsk) vs. whole body temperatures on exercise capacity has not been characterised. To ascertain their relationships with exercise capacity, blood temperature (TB), oxygen uptake (V̇O2), brain perfusion (MCA Vmean), locomotor limb haemodynamics, and haematological parameters were assessed during incremental cycling exercise with elevated skin (mild hyperthermia; HYPmild), combined core and skin temperatures (moderate hyperthermia; HYPmod), and under control conditions. Both hyperthermic conditions increased Tsk vs. control (6.2 ± 0.2 °C; P < 0.001), however, only HYPmod increased resting TB, leg blood flow and cardiac output (Q̇), but not MCA Vmean. Throughout exercise, Tsk remained elevated in both hyperthermic conditions, whereas only TB was greater in HYPmod. At exhaustion, oxygen uptake and exercise capacity were reduced in HYPmod in association with lower leg blood flow, MCA Vmean and MAP, but similar maximal heart rate and TB. The attenuated brain and leg perfusion with hyperthermia was associated with a plateau in MCA and two-legged vascular conductance (VC). Mechanistically, the falling MCA VC was coupled to reductions in PaCO2 whereas the plateau in leg vascular conductance was related to markedly elevated plasma [NA] and a plateau in plasma ATP. These findings reveal that whole-body hyperthermia, but not skin hyperthermia, compromises exercise capacity in heat-stressed humans through the early attenuation of brain and active muscle blood flow.This study was supported by a grant from the Gatorade Sports Science Institute, PepsiCo Inc, USA. The views contained within this document are those of the authors and do not necessarily reflect those of PepsiCo Inc

Temperature and blood flow distribution in the human leg during passive heat stress

The influence of temperature on the hemodynamic adjustments to direct passive heat stress within the leg’s major arterial and venous vessels and compartments remains unclear. Fifteen healthy young males were tested during exposure to either passive whole-body heat stress to levels approaching thermal tolerance (core temperature, Tc + 2 °C; Study 1; n=8) or single leg heat stress (Tc + 0 °C; Study 2; n=7). Whole-body heat stress increased perfusion and decreased oscillatory shear index in relation to the rise in Tleg in all three major arteries supplying the leg - plateauing in the common and superficial femoral arteries prior to reaching severe heat stress levels. Isolated leg heat stress increased arterial blood flows and shear patterns to a level similar to that obtained during moderate core hyperthermia (Tc + 1°C). Despite modest increases in great saphenous venous blood flow (0.2 l/min), the deep venous system accounted for the majority of returning flow (common femoral vein 0.7l/min) during intense to severe levels of heat stress. Rapid cooling of a single leg during severe whole-body heat stress resulted in an equivalent blood flow reduction in the major artery supplying the thigh deep tissues only - suggesting central temperature-sensitive mechanisms contribute to skin blood flow alone. These findings further our knowledge of leg hemodynamic responses during direct heat stress and provide evidence of potentially beneficial vascular alterations during isolated limb heat stress that are equivalent to those experienced during exposure to moderate levels of whole-body hyperthermia

Clinical Efficacy of Brown Seaweeds Ascophyllum nodosum and Fucus vesiculosus in the Prevention or Delay Progression of the Metabolic Syndrome: A Review of Clinical Trials

Metabolic syndrome (MetS) is a global public health problem affecting nearly 25.9% of the world population characterised by a cluster of disorders dominated by abdominal obesity, high blood pressure, high fasting plasma glucose, hypertriacylglycerolaemia and low HDL-cholesterol. In recent years, marine organisms, especially seaweeds, have been highlighted as potential natural sources of bioactive compounds and useful metabolites, with many biological and physiological activities to be used in functional foods or in human nutraceuticals for the management of MetS and related disorders. Of the three groups of seaweeds, brown seaweeds are known to contain more bioactive components than either red and green seaweeds. Among the different brown seaweed species, Ascophyllum nodosum and Fucus vesiculosus have the highest antioxidant values and highest total phenolic content. However, the evidence base relies mainly on cell line and small animal models, with few studies to date involving humans. This review intends to provide an overview of the potential of brown seaweed extracts Ascophyllum nodosum and Fucus vesiculosus for the management and prevention of MetS and related conditions, based on the available evidence obtained from clinical trials

Short-term isothermic heat acclimation elicits beneficial adaptations but medium-term elicits a more complete adaptation

Purpose To investigate the effects of 60 min daily, short-term (STHA) and medium-term (MTHA) isothermic heat acclimation (HA) on the physiological and perceptual responses to exercise heat stress. Methods Sixteen, ultra-endurance runners (female = 3) visited the laboratory on 13 occasions. A 45 min sub-maximal (40% Wmax) cycling heat stress test (HST) was completed in the heat (40 °C, 50% relative humidity) on the first (HSTPRE), seventh (HSTSTHA) and thirteenth (HSTMTHA) visit. Participants completed 5 consecutive days of a 60 min isothermic HA protocol (target Tre 38.5 °C) between HSTPRE and HSTSTHA and 5 more between HSTSTHA and HSTMTHA. Heart rate (HR), rectal (Tre), skin (Tsk) and mean body temperature (Tbody), perceived exertion (RPE), thermal comfort (TC) and sensation (TS) were recorded every 5 min. During HSTs, cortisol was measured pre and post and expired air was collected at 15, 30 and 45 min. Results At rest, Tre and Tbody were lower in HSTSTHA and HSTMTHA compared to HSTPRE, but resting HR was not different between trials. Mean exercising Tre, Tsk, Tbody, and HR were lower in both HSTSTHA and HSTMTHA compared to HSTPRE. There were no differences between HSTSTHA and HSTMTHA. Perceptual measurements were lowered by HA and further reduced during HSTMTHA. Conclusion A 60 min a day isothermic STHA was successful at reducing physiological and perceptual strain experienced when exercising in the heat; however, MTHA offered a more complete adaptation