Thermoregulation during Exercise in the Heat : Strategies for Maintaining Health and Performance

As a result of the inefficiency of metabolic transfer, >75% of the energy that is generated by skeletal muscle substrate oxidation is liberated as heat. During exercise, several powerful physiological mechanisms of heat loss are activated to prevent an excessive rise in body core temperature. However, a hot and humid environment can significantly add to the challenge that physical exercise imposes on the human thermoregulatory system, as heat exchange between body and environment is substantially impaired under these conditions. This can lead to serious performance decrements and an increased risk of developing heat illness. Fortunately, there are a number of strategies that athletes can use to prevent and/or reduce the dangers that are associated with exercise in the heat. In this regard, heat acclimatisation and nutritional intervention seem to be most effective. During heat acclimatisation, the temperature thresholds for both cutaneous vasodilation and the onset of sweating are lowered, which, in combination with plasma volume expansion, improve cardiovascular stability. Effective nutritional interventions include the optimisation of hydration status by the use of fluid replacement beverages. The latter should contain moderate amounts of glucose and sodium, which improve both water absorption and retention

Maternal nutritional status in pastoral versus farming communities of West Pokot, Kenya: differences in iron and vitamin A status and body composition

BACKGROUND: Underweight and micronutrient deficiencies are sequelae of the prevailing harsh living and economic conditions of women in sub-Saharan Africa. There are few data describing maternal nutritional status in these resource-poor settings. Provision of more effective modes of intervention requires that public health and nutrition policy at both the national and the multisectoral levels be based on community-specific nutritional and behavioral practices. OBJECTIVE: This longitudinal study investigated maternal micronutrient status in two remote, semiarid, rural communities that are ethnically similar but have distinctly different pastoral and farming lifestyles. We looked at differences in iron stores, vitamin A levels, and body composition of women in the third trimester of pregnancy and again at 4 months postpartum. METHODS: Complete data were collected from 113 pastoral and 110 farming Pokot women. Anthropometric measurements were taken, and serum ferritin and retinol levels were measured. Infants were weighed within 7 days of birth. RESULTS: Women from the farming community had significantly (p < .05) lower hemoglobin concentrations than women from the pastoral community during the third trimester of pregnancy. Pastoral women had significantly higher serum ferritin concentrations than farming women during the third trimester of pregnancy (p <.05) and at 4 months postpartum. There were no significant differences between pastoral and farming women in the percentage of women with serum retinol levels < 0.70 micromol/L during the third trimester of pregnancy (27.9% [34/113] and 24.2% [31/110], respectively) and at 4 months postpartum (29.2% [33/113] and 30.9% [34/110]) In the farming community, mean infant birthweight was significantly lower (p <. 01) than in the pastoral community and a significantly higher (p < .05) proportion of newborns weighed less than 2.5 kg. At 4 months postpartum, the percentage of body fat was significantly lower in pastoral women than in farming women. CONCLUSIONS: Women from the farming community in West Pokot, Kenya, have lower iron stores during the third trimester of pregnancy than women in the pastoral community. In addition, the mean weight of their newborn infants is lower than that of infants in the pastoral community. These findings may be associated with differences in living conditions, which are usually harsher in farming than in pastoral communities. AD - Department of Epidemiology and Nutrition, School of Public Health, Moi University, Eldoret, Kenya. [email protected]

Thermische comfortmodellen : van statisch naar dynamisch en van groep naar individu

Tzjdens de TVI/L.-excursie naar Laboratorium voor Energie Tech nologie van TUEindhoven is onder andere het onderzoek gepre senteerd naar een dynamisch model voor het berekenen van ther misch comfort. Dit onderzoek is gericht op individuele comfort beleving met o.a. toepassingen in de gezondheidszorg (intensive care units), in extreme omgevingscondities (bi~jv. brandbestrzjding), en voor kleine, individuele werkruimtes. In de bouwwereld wordt veel gebruik gemaakt van het statische model van Fanger [1]. Dit model is echter minder geschikt voor individueel comfort in een dynamische omgeving. Daarom wordt een gedetailleerder dynamisch model gebruikt, dat is ontwikkeld door Fiala et at. [3,4,5]. Dit model is verder verfijnd om indivi duele karakteristieken van deproefiersonen mee te nemen. Aan de hand van experimenten aan proeft’ersonen in klimaatkamers wordt aangetoond dat dit aangepaste modelgoed in staat is om lokale huidtemperaturen bij individuelepersonen te voorspellen

Modulation of thermogenesis and metabolic health:a built environment perspective

\u3cp\u3eLifestyle interventions, obviating the increasing prevalence of the metabolic syndrome, generally focus on nutrition and physical activity. Environmental factors are hardly covered. Because we spend on average more that 90% of our time indoors, it is, however, relevant to address these factors. In the built environment, the attention has been limited to the (assessment and optimization of) building performance and occupant thermal comfort for a long time. Only recently well-being and health of building occupants are also considered to some extent, but actual metabolic health aspects are not generally covered. In this review, we draw attention to the potential of the commonly neglected lifestyle factor ‘indoor environment’. More specifically, we review current knowledge and the developments of new insights into the effects of ambient temperature, light and the interaction of the two on metabolic health. The literature shows that the effects of indoor environmental factors are important additional factors for a healthy lifestyle and have an impact on metabolic health.\u3c/p\u3

Hypoxia induces no change in cutaneous thresholds for warmth and cold sensation

Hypoxia can affect perception of temperature stimuli by impeding thermoregulation at a neural level. Whether this impact on the thermoregulatory response is solely due to affected thermoregulation is not clear, since reaction time may also be affected by hypoxia. Therefore, we studied the effect of hypoxia on thermal perception thresholds for warmth and cold. Thermal perception thresholds were determined in 11 healthy overweight adult males using two methods for small nerve fibre functioning: a reaction-time inclusive method of limits (MLI) and a reaction time exclusive method of levels (MLE). The subjects were measured under normoxic and hypoxic conditions using a cross-over design. Before the thermal threshold tests under hypoxic conditions were conducted, the subjects were acclimatized by staying 14 days overnight (8 h) in a hypoxic tent system (Colorado Altitude Training: 4,000 m). For normoxic measurements the same subjects were not acclimatized, but were used to sleep in the same tent system. Measurements were performed in the early morning in the tent. Normoxic MLI cold sensation threshold decreased significantly from 30.3 ± 0.4 (mean ± SD) to 29.9 ± 0.7°C when exposed to hypoxia (P < 0.05). Similarly, mean normoxic MLI warm sensation threshold increased from 34.0 ± 0.9 to 34.5 ± 1.1°C (P < 0.05). MLE measured threshold for cutaneous cold sensation was 31.4 ± 0.4 and 31.2 ± 0.9°C under respectively normoxic and hypoxic conditions (P > 0.05). Neither was there a significant change in MLE warm threshold comparing normoxic (32.8 ± 0.9°C) with hypoxic condition (32.9 ± 1.0°C) (P > 0.05). Exposure to normobaric hypoxia induces slowing of neural activity in the sensor-to-effector pathway and does not affect cutaneous sensation threshold for either warmth or cold detection

Thermisch comfort in relatie tot laag exergetische HVAC systemen:het ontwerp van een nieuwe klimaatkamer aan de TU Eindhoven en het gebruik van een thermofysiologisch model

Door toepassing van het exergie concept (Iowex) in de gebouwde omgeving kan het gebruik voor hoogwaardige energiebronnen gereduceerd worden. Echter, de toepassing van dergelijke systemen kan resulteren in discomfort, zowel op lichaamsniveau (globaal) als op lokaal niveau. Dit discomfort kan veroorzaakt worden door de combinatie van verschillende niet-uniforme omgevingscondities. Tevredenheid van de gebruikers is echter cruciaal voor het succesvol toepassen van lowex HVAC systemen. Daarom is het van belang om het comfort van de individuele gebruikers onder niet-uniforme en dynamische condities te kunnen voorspellen

Temperature and surgical wound heat loss during orthopedic surgery: computer simulations and measurements

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