The Experts below are selected from a list of 318 Experts worldwide ranked by ideXlab platform
O. Eiken - One of the best experts on this subject based on the ideXlab platform.
-
Motion sickness increases the risk of accidental hypothermia
Eur J Appl Physiol, 2006Co-Authors: Gerard Nobel, Arne Tribukait, Roger Kölegård, O. Eiken, Igor B. MekjavicAbstract:Motion sickness (MS) has been found to increase body-core cooling during Immersion in 28 degrees C water, an effect ascribed to attenuation of the cold-induced peripheral vasoconstriction (Mekjavic et al. in J Physiol 535(2):619-623, 2001). The present study tested the hypothesis that a more profound cold stimulus would override the MS effect on peripheral vasoconstriction and hence on the core cooling rate. Eleven healthy subjects underwent two separate head-out Immersions in 15 degrees C water. In the control trial (CN), subjects were immersed after baseline measurements. In the MS-trial, subjects were rendered motion sick prior to Immersion, by using a rotating chair in combination with a regimen of standardized head movements. During Immersion in the MS-trial, subjects were exposed to an optokinetic stimulus (rotating drum). At 5-min intervals subjects rated their temperature perception, thermal comfort and MS discomfort. During Immersion mean skin temperature, rectal temperature, the difference in temperature between the non-immersed right forearm and 3rd finger of the right hand (DeltaTff), oxygen uptake and heart rate were recorded. In the MS-trial, rectal temperature decreased substantially faster (33%, P < 0.01). Also, the DeltaTff response, an index of peripheral vasomotor tone, as well as the oxygen uptake, indicative of the shivering response, were significantly attenuated (P < 0.01 and P < 0.001, respectively) by MS. Thus, MS may predispose individuals to hypothermia by enhancing heat loss and attenuating heat production. This might have significant implications for survival in maritime accidents.
-
Motion sickness potentiates core cooling during Immersion in humans
Journal of Physiology, 2001Co-Authors: Igor B. Mekjavic, Mikael Gennser, Michael J. Tipton, O. EikenAbstract:1. The present study tested the hypothesis that motion sickness affects thermoregulatory responses to cooling in humans. 2. Ten healthy male volunteers underwent three separate head-out Immersions in 28 degrees C water after different preparatory procedures. In the 'control' procedure Immersion was preceded by a rest period. In the 'motion sickness' procedure Immersion was preceded by provocation of motion sickness in a human centrifuge. This comprised rapid and repeated alterations of the gravitational (G-) stress in the head-to-foot direction, plus a standardized regimen of head movements at increased G-stress. In the 'G-control' procedure, the subjects were exposed to similar G-stress, but without the motion sickness provocation. 3. During Immersion mean skin temperature, rectal temperature, the difference in temperature between the forearm and 3rd digit of the right hand (DeltaT(forearm-fingertip)), oxygen uptake and heart rate were recorded. Subjects provided ratings of temperature perception, thermal comfort and level of motion sickness discomfort at regular intervals. 4. No differences were observed in any of the variables between control and G-control procedures. In the motion sickness procedure, the DeltaT(forearm-fingertip) response was significantly attenuated, indicating a blunted vasoconstrictor response, and rectal temperature decreased at a faster rate. No other differences were observed. 5. Motion sickness attenuates the vasoconstrictor response to skin and core cooling, thereby enhancing heat loss and the magnitude of the fall in deep body temperature. Motion sickness may predispose individuals to hypothermia, and have significant implications for survival time in maritime accidents.
Igor B. Mekjavic - One of the best experts on this subject based on the ideXlab platform.
-
Motion sickness increases the risk of accidental hypothermia
Eur J Appl Physiol, 2006Co-Authors: Gerard Nobel, Arne Tribukait, Roger Kölegård, O. Eiken, Igor B. MekjavicAbstract:Motion sickness (MS) has been found to increase body-core cooling during Immersion in 28 degrees C water, an effect ascribed to attenuation of the cold-induced peripheral vasoconstriction (Mekjavic et al. in J Physiol 535(2):619-623, 2001). The present study tested the hypothesis that a more profound cold stimulus would override the MS effect on peripheral vasoconstriction and hence on the core cooling rate. Eleven healthy subjects underwent two separate head-out Immersions in 15 degrees C water. In the control trial (CN), subjects were immersed after baseline measurements. In the MS-trial, subjects were rendered motion sick prior to Immersion, by using a rotating chair in combination with a regimen of standardized head movements. During Immersion in the MS-trial, subjects were exposed to an optokinetic stimulus (rotating drum). At 5-min intervals subjects rated their temperature perception, thermal comfort and MS discomfort. During Immersion mean skin temperature, rectal temperature, the difference in temperature between the non-immersed right forearm and 3rd finger of the right hand (DeltaTff), oxygen uptake and heart rate were recorded. In the MS-trial, rectal temperature decreased substantially faster (33%, P < 0.01). Also, the DeltaTff response, an index of peripheral vasomotor tone, as well as the oxygen uptake, indicative of the shivering response, were significantly attenuated (P < 0.01 and P < 0.001, respectively) by MS. Thus, MS may predispose individuals to hypothermia by enhancing heat loss and attenuating heat production. This might have significant implications for survival in maritime accidents.
-
Motion sickness potentiates core cooling during Immersion in humans
Journal of Physiology, 2001Co-Authors: Igor B. Mekjavic, Mikael Gennser, Michael J. Tipton, O. EikenAbstract:1. The present study tested the hypothesis that motion sickness affects thermoregulatory responses to cooling in humans. 2. Ten healthy male volunteers underwent three separate head-out Immersions in 28 degrees C water after different preparatory procedures. In the 'control' procedure Immersion was preceded by a rest period. In the 'motion sickness' procedure Immersion was preceded by provocation of motion sickness in a human centrifuge. This comprised rapid and repeated alterations of the gravitational (G-) stress in the head-to-foot direction, plus a standardized regimen of head movements at increased G-stress. In the 'G-control' procedure, the subjects were exposed to similar G-stress, but without the motion sickness provocation. 3. During Immersion mean skin temperature, rectal temperature, the difference in temperature between the forearm and 3rd digit of the right hand (DeltaT(forearm-fingertip)), oxygen uptake and heart rate were recorded. Subjects provided ratings of temperature perception, thermal comfort and level of motion sickness discomfort at regular intervals. 4. No differences were observed in any of the variables between control and G-control procedures. In the motion sickness procedure, the DeltaT(forearm-fingertip) response was significantly attenuated, indicating a blunted vasoconstrictor response, and rectal temperature decreased at a faster rate. No other differences were observed. 5. Motion sickness attenuates the vasoconstrictor response to skin and core cooling, thereby enhancing heat loss and the magnitude of the fall in deep body temperature. Motion sickness may predispose individuals to hypothermia, and have significant implications for survival time in maritime accidents.
Christopher J Stevens - One of the best experts on this subject based on the ideXlab platform.
-
how does a delay between temperate running exercise and hot water Immersion alter the acute thermoregulatory response and heat load
Frontiers in Physiology, 2019Co-Authors: Storme L Heathcote, Peter Hassmen, Shi Zhou, Lee Taylor, Christopher J StevensAbstract:Hot-water Immersion following exercise in a temperate environment can elicit heat acclimation in endurance-trained individuals. However, a delay between exercise cessation and Immersion is likely a common occurrence in practice. Precisely how such a delay potentially alters hot-water Immersion mediated acute physiological responses (e.g. total heat-load) remains unexplored. Such data would aid in optimising prescription of post-exercise hot-water Immersion in cool environments, relative to heat acclimation goals. Twelve male recreational runners (mean ± SD; age: 38 ± 13 y, height: 180 ± 7 cm, body mass: 81 ± 13.7 kg, body fat: 13.9 ± 3.5%) completed three separate 40-minute treadmill runs (18°C), followed by either a 10 min (10M), 1 h (1H) or 8 h (8H) delay, prior to a 30-minute hot-water Immersion (39°C), with a randomised crossover design. Core and skin temperatures, heart rate, sweat and perceptual responses were measured across the trials. Mean core temperature during Immersion was significantly lower in 1H (37.39 ± 0.30°C) compared to 10M (37.83 ± 0.24°C; P = 0.0032) and 8H (37.74 ± 0.19°C; P = 0.0140). Mean skin temperature was significantly higher in 8H (32.70 ± 0.41°C) compared to 10M (31.93 ± 0.60°C; P = 0.0042) at the end of the hot-water Immersion. Mean and maximal heart rates were also higher during Immersion in 10M compared to 1H and 8H (P < 0.05), despite no significant differences in the sweat or perceptual responses. The shortest delay between exercise and Immersion (10M) provoked the greatest heat-load during Immersion. However, performing the hot-water Immersion in the afternoon (8H), which coincided with peak circadian body temperature, provided a larger heat-load stimulus than the 1 h delay (1H).
Dehua Wang - One of the best experts on this subject based on the ideXlab platform.
-
Isometric Immersions and compensated compactness
Communications in Mathematical Physics, 2010Co-Authors: Gui Qiang Chen, Marshall Slemrod, Dehua WangAbstract:A fundamental problem in differential geometry is to characterize intrinsic metrics on a two-dimensional Riemannian manifold ${\mathcal M}^2$ which can be realized as isometric Immersions into $\R^3$. This problem can be formulated as initial and/or boundary value problems for a system of nonlinear partial differential equations of mixed elliptic-hyperbolic type whose mathematical theory is largely incomplete. In this paper, we develop a general approach, which combines a fluid dynamic formulation of balance laws for the Gauss-Codazzi system with a compensated compactness framework, to deal with the initial and/or boundary value problems for isometric Immersions in $\R^3$. The compensated compactness framework formed here is a natural formulation to ensure the weak continuity of the Gauss-Codazzi system for approximate solutions, which yields the isometric realization of two-dimensional surfaces in $\R^3$. As a first application of this approach, we study the isometric Immersion problem for two-dimensional Riemannian manifolds with strictly negative Gauss curvature. We prove that there exists a $C^{1,1}$ isometric Immersion of the two-dimensional manifold in $\R^3$ satisfying our prescribed initial conditions. T
Michael J. Tipton - One of the best experts on this subject based on the ideXlab platform.
-
Motion sickness potentiates core cooling during Immersion in humans
Journal of Physiology, 2001Co-Authors: Igor B. Mekjavic, Mikael Gennser, Michael J. Tipton, O. EikenAbstract:1. The present study tested the hypothesis that motion sickness affects thermoregulatory responses to cooling in humans. 2. Ten healthy male volunteers underwent three separate head-out Immersions in 28 degrees C water after different preparatory procedures. In the 'control' procedure Immersion was preceded by a rest period. In the 'motion sickness' procedure Immersion was preceded by provocation of motion sickness in a human centrifuge. This comprised rapid and repeated alterations of the gravitational (G-) stress in the head-to-foot direction, plus a standardized regimen of head movements at increased G-stress. In the 'G-control' procedure, the subjects were exposed to similar G-stress, but without the motion sickness provocation. 3. During Immersion mean skin temperature, rectal temperature, the difference in temperature between the forearm and 3rd digit of the right hand (DeltaT(forearm-fingertip)), oxygen uptake and heart rate were recorded. Subjects provided ratings of temperature perception, thermal comfort and level of motion sickness discomfort at regular intervals. 4. No differences were observed in any of the variables between control and G-control procedures. In the motion sickness procedure, the DeltaT(forearm-fingertip) response was significantly attenuated, indicating a blunted vasoconstrictor response, and rectal temperature decreased at a faster rate. No other differences were observed. 5. Motion sickness attenuates the vasoconstrictor response to skin and core cooling, thereby enhancing heat loss and the magnitude of the fall in deep body temperature. Motion sickness may predispose individuals to hypothermia, and have significant implications for survival time in maritime accidents.
