Role of skin blood flow and sweating rate in exercise  thermoregulation after bed rest

Lee, Stuart M. C.; Williams, W. Jon; Schneider, Suzanne M.

doi:10.1152/japplphysiol.00105.2001

Cited by 29 publications

(47 citation statements)

References 33 publications

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“…The gain of the V _ O 2 /D Tre response is attenuated in the Post-bedrest trial, reflecting an attenuation of shivering thermogenesis would be less prominent, due to the fairly rapid recovery of plasma volume following the cessation of bed-rest (Fortney et al 1991). Our findings are in agreement with those of Greenleaf and Reese (1980) and Lee et al (2002), who reported no effects of bed-rest on the gain and magnitude of the sweating response after 14 days of bed-rest. In contrast to Lee et al (2002), who noted a delay in the onset of the sweating response, we did not observe such a shift in the core temperature threshold for onset of sweating.…”

Section: Exercise Temperature Regulationsupporting

confidence: 93%

“…Our findings are in agreement with those of Greenleaf and Reese (1980) and Lee et al (2002), who reported no effects of bed-rest on the gain and magnitude of the sweating response after 14 days of bed-rest. In contrast to Lee et al (2002), who noted a delay in the onset of the sweating response, we did not observe such a shift in the core temperature threshold for onset of sweating.…”

Section: Exercise Temperature Regulationsupporting

confidence: 93%

“…This has been confirmed by bed-rest and post-flight experiments, noting that inactivity or prolonged exposure to microgravity causes impairment in exercise thermoregulation (Fortney 1987;Crandall et al 1994;Lee et al 2002). Specifically, there is a greater exercise-induced increase in core temperature (Greenleaf and Reese 1980;Greenleaf 1989), attributed to impaired sweating (Greenleaf and Reese 1980;Fortney 1987;Fortney et al 1998;Lee et al 2002) and vasodilatory responses (Williams and Reese 1976;Crandall et al 1994;Fortney et al 1998;Lee et al 2002).…”

Section: Introductionmentioning

confidence: 86%

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Human thermoregulatory function during exercise and immersion after 35 days of horizontal bed-rest and recovery

et al. 2005

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The present study evaluated the effect of 35 days of experimental horizontal bed-rest on exercise and immersion thermoregulatory function. Fifteen healthy male volunteers were assigned to either a Control (n = 5) or Bed-rest (n = 10) group. Thermoregulatory function was evaluated during a 30-min bout of submaximal exercise on a cycle ergometer, followed immediately by a 100-min immersion in 28 degrees C water. For the Bed-rest group, exercise and immersion thermoregulatory responses observed post-bed-rest were compared with those after a 5 week supervised active recovery period. In both trials, the absolute work load during the exercise portion of the test was identical. During the exercise and immersion, we recorded skin temperature, rectal temperature, the difference in temperature between the forearm and third digit of the right hand (DeltaT(forearm-fingertip))--an index of skin blood flow, sweating rate from the forehead, oxygen uptake and heart rate at minute intervals. Subjects provided ratings of temperature perception and thermal comfort at 5-min intervals. Exercise thermoregulatory responses after bed-rest and recovery were similar. Subjective ratings of temperature perception and thermal comfort during immersion indicated that subjects perceived similar combinations of Tsk and Tre to be warmer and thermally less uncomfortable after bed-rest. The average (SD) exercise-induced increase in Tre relative to resting values was not significantly different between the Post-bed-rest (0.4 (0.2) degrees C) and Recovery (0.5 (0.2) degrees C) trials. During the post-exercise immersion, the decrease in Tre, relative to resting values, was significantly (P < 0.05) greater in the Post-bed-rest trial (0.9 (0.5) degrees C) than after recovery (0.4 (0.3) degrees C). DeltaT(forearm-fingertip) was 5.2 (0.9) degrees C and 5.8 (1.0) degrees C at the end of the post-bed-rest and recovery immersions, respectively. The gain of the shivering response (increase in VO(2) relative to the decrease in Tre; VO(2)/Tre) was 1.19 l min(-1) degrees C(-1) in the Recovery trial, and was significantly attenuated to 0.51 l min(-1) degrees C(-1) in the Post-bed-rest trial. The greater cooling rate observed in the post-bed-rest trial is attributed to the greater heat loss and reduced heat production. The former is the result of attenuated cold-induced vasoconstriction and enhanced sweating rate, and the latter a result of a lower shivering VO(2) response.

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Section: Exercise Temperature Regulationsupporting

confidence: 93%

Section: Exercise Temperature Regulationsupporting

confidence: 93%

Section: Introductionmentioning

confidence: 86%

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Human thermoregulatory function during exercise and immersion after 35 days of horizontal bed-rest and recovery

et al. 2005

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“…This team studied maximal forearm cutaneous vascular conductance (plethysmography) and sweat gland function (acetylcholine intradermal microdialysis) during a 14-day HDBR. Lee et al (2002) suggest a centrally mediated elevation in the thermoregulatory set point during bed rest exposure.…”

Section: Decrease In Exercise Capacitymentioning

confidence: 90%

From space to Earth: advances in human physiology from 20 years of bed rest studies (1986–2006)

Traon¹,

et al. 2007

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Bed rest studies of the past 20 years are reviewed. Head-down bed rest (HDBR) has proved its usefulness as a reliable simulation model for the most physiological effects of spaceflight. As well as continuing to search for better understanding of the physiological changes induced, these studies focused mostly on identifying effective countermeasures with encouraging but limited success. HDBR is characterised by immobilization, inactivity, confinement and elimination of Gz gravitational stimuli, such as posture change and direction, which affect body sensors and responses. These induce upward fluid shift, unloading the body's upright weight, absence of work against gravity, reduced energy requirements and reduction in overall sensory stimulation. The upward fluid shift by acting on central volume receptors induces a 10-15% reduction in plasma volume which leads to a now well-documented set of cardiovascular changes including changes in cardiac performance and baroreflex sensitivity that are identical to those in space. Calcium excretion is increased from the beginning of bed rest leading to a sustained negative calcium balance. Calcium absorption is reduced. Body weight, muscle mass, muscle strength is reduced, as is the resistance of muscle to insulin. Bone density, stiffness of bones of the lower limbs and spinal cord and bone architecture are altered. Circadian rhythms may shift and are dampened. Ways to improve the process of evaluating countermeasures--exercise (aerobic, resistive, vibration), nutritional and pharmacological--are proposed. Artificial gravity requires systematic evaluation. This review points to clinical applications of BR research revealing the crucial role of gravity to health.

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“…For example, reduced endothelium-mediated vasodilatory responses have been reported in vivo (65) and in vitro (12,13,25,33,55,65,71) after hindlimb unloading in rats. In addition, reduced dilation has been reported in the vasculatures of the forearm in patients on bed rest (10,11,29,57) and in astronauts after long-term spaceflight (17). We and others (25,55,65) have hypothesized that reduced NO dilation may contribute to attenuated exerciseinduced skeletal muscle vasodilation and reduced exercise capacity observed after hindlimb unloading (14, 46, 64) and , and systemic NOS (20 mg/kg L-NAME) in control (n ϭ 8) and HU rats (n ϭ 6).…”

Section: Discussionmentioning

confidence: 99%

Hindlimb unloading alters nitric oxide and autonomic control of resting arterial pressure in conscious rats

Mueller

Foley

Hasser

2005

American Journal of Physiology-Regulatory, Integrative and Comp

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After periods of microgravity or bed rest, individuals often exhibit reduced Vo(2 max), hypovolemia, cardiac and vascular effects, and autonomic dysfunction. Recently, alterations in expression of vascular and central nervous system NO synthase (NOS) have been observed in hindlimb-unloaded (HU) rats, a model used to simulate physiological effects of microgravity or bed rest. We examined the effects of 14 days of hindlimb unloading on hemodynamic responses to systemic NOS inhibition in conscious control and HU rats. Because differences in NO and autonomic regulation might occur after hindlimb unloading, we also evaluated potential differences in resting autonomic tone and effects of NOS inhibition after autonomic blockade. Administration of nitro-L-arginine methyl ester (L-NAME; 20 mg/kg iv) increased mean arterial pressure (MAP) to similar levels in control and HU rats. However, the change in MAP in response to L-NAME was less in HU rats, that had an elevated baseline MAP. In separate experiments, atropine (1 mg/kg iv) increased heart rate (HR) in control but not HU rats. Subsequent administration of the ganglionic blocker hexamethonium (30 mg/kg iv) decreased MAP and HR to a greater extent in HU rats. Administration of L-NAME after autonomic blockade increased MAP in both groups to a greater extent compared with intact conditions. However, the pressor response to L-NAME was still reduced in HU rats. These data suggest that hindlimb unloading in rats reduces peripheral NO as well as cardiac parasympathetic tone. Along with elevations in sympathetic tone, these effects likely contribute to alterations in vascular control and changes in autonomic reflex function following spaceflight or bed rest.

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Role of skin blood flow and sweating rate in exercise thermoregulation after bed rest

Cited by 29 publications

References 33 publications

Human thermoregulatory function during exercise and immersion after 35 days of horizontal bed-rest and recovery

Human thermoregulatory function during exercise and immersion after 35 days of horizontal bed-rest and recovery

From space to Earth: advances in human physiology from 20 years of bed rest studies (1986–2006)

Hindlimb unloading alters nitric oxide and autonomic control of resting arterial pressure in conscious rats

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