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Moyen NE, Ediger TR, Taylor KM, Hancock EG, Holden LD, Tracy EE, Kay PH, Irick CR, Kotzen KJ, He DD. Sleeping for One Week on a Temperature-Controlled Mattress Cover Improves Sleep and Cardiovascular Recovery. Bioengineering (Basel) 2024; 11:352. [PMID: 38671774 PMCID: PMC11048088 DOI: 10.3390/bioengineering11040352] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2024] [Revised: 03/19/2024] [Accepted: 03/31/2024] [Indexed: 04/28/2024] Open
Abstract
Body temperature should be tightly regulated for optimal sleep. However, various extrinsic and intrinsic factors can alter body temperature during sleep. In a free-living study, we examined how sleep and cardiovascular health metrics were affected by sleeping for one week with (Pod ON) vs. without (Pod OFF), an active temperature-controlled mattress cover (the Eight Sleep Pod). A total of 54 subjects wore a home sleep test device (HST) for eight nights: four nights each with Pod ON and OFF (>300 total HST nights). Nightly sleeping heart rate (HR) and heart rate variability (HRV) were collected. Compared to Pod OFF, men and women sleeping at cooler temperatures in the first half of the night significantly improved deep (+14 min; +22% mean change; p = 0.003) and REM (+9 min; +25% mean change; p = 0.033) sleep, respectively. Men sleeping at warm temperatures in the second half of the night significantly improved light sleep (+23 min; +19% mean change; p = 0.023). Overall, sleeping HR (-2% mean change) and HRV (+7% mean change) significantly improved with Pod ON (p < 0.01). To our knowledge, this is the first study to show a continuously temperature-regulated bed surface can (1) significantly modify time spent in specific sleep stages in certain parts of the night, and (2) enhance cardiovascular recovery during sleep.
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Greenfield AM, Alba BK, Giersch GEW, Seeley AD. Sex differences in thermal sensitivity and perception: Implications for behavioral and autonomic thermoregulation. Physiol Behav 2023; 263:114126. [PMID: 36787810 DOI: 10.1016/j.physbeh.2023.114126] [Citation(s) in RCA: 13] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2022] [Revised: 01/20/2023] [Accepted: 02/10/2023] [Indexed: 02/16/2023]
Abstract
Temperature sensitive receptors in the skin and deep body enable the detection of the external and internal environment, including the perception of thermal stimuli. Changes in heat balance require autonomic (e.g., sweating) and behavioral (e.g., seeking shade) thermoeffector initiation to maintain thermal homeostasis. Sex differences in body morphology can largely, but not entirely, account for divergent responses in thermoeffector and perceptual responses to environmental stress between men and women. Thus, it has been suggested that innate differences in thermosensation may exist between men and women. Our goal in this review is to summarize the existing literature that investigates localized and whole-body cold and heat exposure pertaining to sex differences in thermal sensitivity and perception, and the interplay between autonomic and behavioral thermoeffector responses. Overall, it appears that local differences in thermal sensitivity and perception are minimized, yet still apparent, when morphological characteristics are well-controlled. Sex differences in the early vasomotor response to environmental stress and subsequent changes in blood flow likely contribute to the heightened thermal awareness observed in women. However, the contribution of thermoreceptors to observed sex differences in thermal perception and thermoeffector function is unclear, as human studies investigating these questions have not been performed.
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Affiliation(s)
- Andrew M Greenfield
- Thermal and Mountain Medicine Division, US Army Research Institute of Environmental Medicine, Natick, MA, United States of America; Oak Ridge Institute for Science and Education, Belcamp, MD, United States of America.
| | - Billie K Alba
- Thermal and Mountain Medicine Division, US Army Research Institute of Environmental Medicine, Natick, MA, United States of America
| | - Gabrielle E W Giersch
- Thermal and Mountain Medicine Division, US Army Research Institute of Environmental Medicine, Natick, MA, United States of America
| | - Afton D Seeley
- Thermal and Mountain Medicine Division, US Army Research Institute of Environmental Medicine, Natick, MA, United States of America
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Corbett J, Wright J, Tipton MJ. Sex differences in response to exercise heat stress in the context of the military environment. BMJ Mil Health 2023; 169:94-101. [PMID: 32094215 DOI: 10.1136/jramc-2019-001253] [Citation(s) in RCA: 10] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2019] [Revised: 08/08/2019] [Accepted: 08/11/2019] [Indexed: 01/26/2023]
Abstract
Women can now serve in ground close combat (GCC) roles, where they may be required to operate alongside men in hot environments. However, relative to the average male soldier, female soldiers are less aerobically fit, with a smaller surface area (A D), lower mass (m) with higher body fat and a larger A D/m ratio. This increases cardiovascular strain, reduces heat exchange with the environment and causes a greater body temperature increase for a given heat storage, although a large A D/m ratio can be advantageous. Physical employment standards for GCC roles might lessen the magnitude of fitness and anthropometric differences, yet even when studies control for these factors, women sweat less than men at high work rates. Therefore, the average female soldier in a GCC role is likely to be at a degree of disadvantage in many hot environments and particularly during intense physical activity in hot-arid conditions, although heat acclimation may mitigate some of this effect. Any thermoregulatory disadvantage may be exacerbated during the mid-luteal phase of the menstrual cycle, although the data are equivocal. Likewise, sex differences in behavioural thermoregulation and cognition in the heat are not well understood. Interestingly, there is often lower reported heat illness incidence in women, although the extent to which this is influenced by behavioural factors or historic differences in role allocation is unclear. Indeed, much of the extant literature lacks ecological validity and more work is required to fully understand sex differences to exercise heat stress in a GCC context.
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Affiliation(s)
- Jo Corbett
- School of Sport, Health and Exercise Science, University of Portsmouth, Portsmouth, UK
| | - J Wright
- School of Sport, Health and Exercise Science, University of Portsmouth, Portsmouth, UK.,Reserach Associate, British Army, London, UK
| | - M J Tipton
- School of Sport, Health and Exercise Science, University of Portsmouth, Portsmouth, UK
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Seo Y, Kim JH. Differential Cutaneous Thermal Sensitivity in Humans: Method of Limit vs. Method of Sensation Magnitude. INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 2021; 18:ijerph182312576. [PMID: 34886305 PMCID: PMC8657088 DOI: 10.3390/ijerph182312576] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/03/2021] [Revised: 11/25/2021] [Accepted: 11/26/2021] [Indexed: 11/16/2022]
Abstract
INTRODUCTION The method of limits (MLI) and method of level (MLE) are commonly employed for the quantitative assessment of cutaneous thermal sensitivity. Thermal sensation and thermal comfort are closely related and thermal sensations evoked from the peripheral thermoreceptors play an important role in thermoregulatory response to maintain normal body temperature. The purpose of this study was to compare the regional distribution of cutaneous warm and cold sensitivity between MLI and the method of sensation magnitude (MSM). METHOD Twenty healthy men completed MLI and MSM to compare the regional distribution of cutaneous warm and cold sensitivity in the thermal neutral condition. The subjects rested on a bed in a supine position for 20 min. Next, the cutaneous thermal sensitivity of ten body sites was assessed by the means of MLI and MSM for both warmth and cold stimuli. RESULTS The absolute mean heat flux in MLI and thermal sensation magnitude in MSM showed significantly greater sensitivity to cold than to warm stimulation (p < 0.01), together with a similar pattern of regional differences across ten body sites. Both sensory modalities indicated acceptable reliability (SRD%: 6.29-8.66) and excellent reproducibility (ICC: 0.826-0.906; p < 0.01). However, the Z-sore distribution in MSM was much narrower than in MLI, which may limit the test sensitivity for the detection of sensory disorders and/or comparison between individuals. CONCLUSION The present results showed that both MLI and MSM are effective means for evaluating regional cutaneous thermal sensitivity to innocuous warm and cold stimulations to a strong degree of reliability and reproducibility.
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Affiliation(s)
- Yongsuk Seo
- Sports AIX Graduate Program, Pohang University of Science and Technology, Pohang 37673, Korea;
| | - Jung-Hyun Kim
- Department of Sports Medicine, Kyung Hee University, Yongin-si 17104, Korea
- Correspondence:
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Mekjavic IB, Yogev D, Ciuha U. Perception of Thermal Comfort during Skin Cooling and Heating. Life (Basel) 2021; 11:life11070681. [PMID: 34357053 PMCID: PMC8303551 DOI: 10.3390/life11070681] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2021] [Revised: 07/09/2021] [Accepted: 07/10/2021] [Indexed: 11/16/2022] Open
Abstract
Due to the static and dynamic activity of the skin temperature sensors, the cutaneous thermal afferent information is dependent on the rate and direction of the temperature change, which would suggest different perceptions of temperature and of thermal comfort during skin heating and cooling. This hypothesis was tested in the present study. Subjects (N = 12; 6 females and 6 males) donned a water-perfused suit (WPS) in which the temperature was varied in a saw-tooth manner in the range from 27 to 42 °C. The rate of change of temperature of the water perfusing the suit (TWPS) was 1.2 °C min-1 during both the heating and cooling phases. The trial was repeated thrice, with subjects reporting their perception of the temperature and thermal comfort at each 3 °C change in TWPS. In addition, subjects were instructed to report when they perceived TWPS uncomfortably cool and warm during cooling and heating, respectively. Subjects reproducibly identified the boundaries of their Thermal Comfort Zone (TCZ), defined as the lower (Tlow) and upper (Thigh) temperatures at which subjects reported slight thermal discomfort. During the heating phase, Tlow and Thigh were 30.0 ± 1.5 °C and 35.1 ± 2.9 °C, respectively. During the cooling phase, the boundary temperatures of Tlow and Thigh were 35.4 ± 1.9 °C and 38.7 ± 2.3 °C, respectively. The direction of the change in the cutaneous temperature stimulus affects the boundaries of the TCZ, such that they are higher during cooling and lower during heating. These findings are explained on the basis of the neurophysiology of thermal perception. From an applied perspective, the most important observation of the present study was the strong correlation between the perception of thermal comfort and the behavioral regulation of thermal comfort. Although it is not surprising that the action of regulating thermal comfort is aligned with its perception, this link has not been proven for humans in previous studies. The results therefore provide a sound basis to consider ratings of thermal comfort as reflecting behavioral actions to achieve the sensation of thermal neutrality.
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Heat acclimation does not modify autonomic responses to core cooling and the skin thermal comfort zone. J Therm Biol 2020; 91:102602. [PMID: 32716857 DOI: 10.1016/j.jtherbio.2020.102602] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2019] [Revised: 04/14/2020] [Accepted: 04/16/2020] [Indexed: 11/23/2022]
Abstract
Exercise heat acclimation (HA) is known to magnify the sweating response by virtue of a lower threshold as well as increased gain and maximal capacity of sweating. However, HA has been shown to potentiate the shivering response in a cold-air environment. We investigated whether HA would alter heat loss and heat production responses during water immersion. Twelve healthy male participants underwent a 10-day HA protocol comprising daily 90-min controlled-hyperthermia (target rectal temperature, Tre 38.5 °C) exercise sessions. Preceding and following HA, the participants performed a maximal exercise test in thermoneutral conditions (ambient temperature 23 °C, relative humidity 50%) and were, following exercise, immersed in 28 °C water for 60 min. Thermal comfort zone (TCZ) was also assessed with participants regulating the temperature of a water-perfused suit during heating and cooling. Baseline pre-immersion Tre was similar pre- and post-HA (pre: 38.33 ± 0.33 °C vs post: 38.12 ± 0.36 °C, p = 0.092). The Tre cooling rate was identical pre-to post-HA (-0.03 ± 0.01 °C·min-1, p = 0.31), as was the vasomotor response reflected in the forearm-fingertip temperature difference. Shivering thresholds (p = 0.43) and gains (p = 0.61) were not affected by HA. TCZ was established at similar temperatures, with the magnitude in regulated water temperature being 7.6 (16.3) °C pre-HA and 5.1 (24.7) °C post-HA (p = 0.65). The present findings suggest that heat production and heat loss responses during whole body cooling as well as the skin thermal comfort zone remained unaltered by a controlled-hyperthermia HA protocol.
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Ciuha U, Kounalakis S, McDonnell AC, Mekjavic IB. Seasonal variation of temperature regulation: do thermoregulatory responses "spring" forward and "fall" back? INTERNATIONAL JOURNAL OF BIOMETEOROLOGY 2020; 64:1221-1231. [PMID: 32193595 DOI: 10.1007/s00484-020-01898-w] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/27/2019] [Revised: 03/06/2020] [Accepted: 03/08/2020] [Indexed: 06/10/2023]
Abstract
Seasonal variations in day length and light intensity can affect the circadian rhythm as well as some characteristics of temperature regulation. We investigated characteristics of autonomic (ATR), behavioural (BTR) and nocturnal (NTR) temperature regulation during spring and autumn. Eleven participants underwent experiments in both seasons. To assess ATR, participants performed a 30-min bout of submaximal upright exercise on a cycle ergometer, followed by 100 min of water immersion (28 °C). Thresholds for the onset of shivering and sweating and vasomotor response were measured. BTR was assessed using a water-perfused suit, with participants regulating the water-perfused suit temperature (Twps) within a range, considered as thermally comfortable. The Twps changed in a saw-tooth manner from 10 to 50 °C; by depressing a switch, the direction of the Twps changed, and this limit defined the thermal comfort zone (TCZ) for each participant. A 24-h proximal (calf)-distal (toe) skin temperature gradient (∆Tc-t) was measured to assess NTR. Initiation of vasomotor tone, shivering and sweating was similar between trials. Width of the TCZ was 8.1 °C in spring and 8.6 °C in autumn (p = 0.1), with similar upper and lower regulated temperatures. ∆Tc-t exhibited a typical circadian rhythm with no difference between seasons. Minor changes in skin temperature and oxygen consumption (p ˂ 0.05) between the seasons may indicate a degree of seasonal adaptation over the course of winter and summer, which persisted in spring and autumn. Other factors, such as country, race, sex and age could however modify the outcome of the study.
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Affiliation(s)
- Urša Ciuha
- Department of Automation, Biocybernetics and Robotics, Jozef Stefan Institute, Jamova 39, SI-1000, Ljubljana, Slovenia.
| | | | - Adam C McDonnell
- Department of Automation, Biocybernetics and Robotics, Jozef Stefan Institute, Jamova 39, SI-1000, Ljubljana, Slovenia
| | - Igor B Mekjavic
- Department of Automation, Biocybernetics and Robotics, Jozef Stefan Institute, Jamova 39, SI-1000, Ljubljana, Slovenia
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, Buranby, British Columbia, V5A 1S6, Canada
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Ciuha U, Tobita K, McDonnell AC, Mekjavic IB. The effect of thermal transience on the perception of thermal comfort. Physiol Behav 2019; 210:112623. [PMID: 31325511 DOI: 10.1016/j.physbeh.2019.112623] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2019] [Revised: 06/18/2019] [Accepted: 07/16/2019] [Indexed: 11/26/2022]
Abstract
INTRODUCTION The present study tested the hypothesis that at any given ambient temperature (Ta), thermal comfort (TC) is not only a function of the temperature per se, but is also influenced by the temperatures rate of change and direction. METHODS Twelve healthy young (age: 23 ± 3) male participants completed experimental trials where Ta increased from 15° to 40 °C (heating) and then decreased from 40 to 15 °C (cooling). In one trial (FAST), the rate of change in Ta was maintained at 1 °C.min-1, and in the other (SLOW) at 0.5 °C.min-1. During each trial participants provided ratings of TC at 3-min intervals to determine their thermal comfort zone (TCZ). RESULTS In the FAST trial, participants identified TCZ at an Ta between 22 ± 4 and 30 ± 4 °C during heating and between 25 ± 3 and 33 ± 3 °C during cooling phase (p = .003), and in the SLOW trial between 21 ± 3 and 33 ± 4 °C during heating and between 23 ± 4 and 34 ± 3 °C during cooling phase (p = .012). During the heating phase TCZ was established at a lower range of Ta, compared to cooling phase. The difference between the heating and cooling phases in preferred range of Ta was more pronounced in the FAST compared to SLOW trial. CONCLUSION TCZ is influenced not only by the prevailing temperature, but also by the direction and the rate of the change in Ta. Faster changes in Ta (1 °C.min-1) established the TCZ at a higher Ta during cooling and at a lower Ta during heating phase.
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Affiliation(s)
- Urša Ciuha
- Department of Automation, Biocybernetics and Robotics, Jozef Stefan Institute, Jamova 39, SI-1000 Ljubljana, Slovenia.
| | - Kunihito Tobita
- Department of Automation, Biocybernetics and Robotics, Jozef Stefan Institute, Jamova 39, SI-1000 Ljubljana, Slovenia; Department of Sustainable System Sciences, Osaka Prefecture University, 1-1 Gakuen-cho, Naka-ku, Sakai, Osaka 599-8531, Japan
| | - Adam C McDonnell
- Department of Automation, Biocybernetics and Robotics, Jozef Stefan Institute, Jamova 39, SI-1000 Ljubljana, Slovenia
| | - Igor B Mekjavic
- Department of Automation, Biocybernetics and Robotics, Jozef Stefan Institute, Jamova 39, SI-1000 Ljubljana, Slovenia; Department of Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, British Columbia V5A 1S6, Canada
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Kakitsuba N. Effect of change in ambient temperature on core temperature of female subjects during the daytime and its sex differences. INTERNATIONAL JOURNAL OF BIOMETEOROLOGY 2019; 63:1069-1076. [PMID: 31020393 DOI: 10.1007/s00484-019-01721-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/17/2018] [Revised: 02/14/2019] [Accepted: 04/04/2019] [Indexed: 06/09/2023]
Abstract
Tympanic temperature (Tty), skin temperature, and regional dry heat loss were measured continuously in eight female subjects under three conditions: (1) stepwise increases in ambient temperature (Ta) from 26 °C at 09:00 to 30 °C at 18:00, (2) steady Ta at 28 °C from 09:00 to 18:00, and (3) stepwise decreases in Ta from 30 °C at 09:00 to 26 °C at 18:00. Oxygen consumption, body weight loss, thermal sensation, and comfort levels were periodically recorded. The Tty increased significantly (p < 0.01) from 36.1 ± 0.36 °C to 36.6 ± 0.23 °C at 18:00 under condition 1 but remained virtually unchanged under conditions 2 and 3. Thermal comfort was observed at 15:00 and 17:00 under condition 3, whereas subjects reported that they felt slightly cool at 15:00. The rate of body heat storage (S), changes in Tty, mean skin temperature ([Formula: see text]sk), and mean body temperature during each period were calculated, and confirmed that changes in [Formula: see text]sk was correlated with S. Diurnal changes in core temperature (Tc) appeared to be more dependent on diurnal rhythm than on changes in Ta, except when Ta increased continuously. Thus, it may be difficult to predict diurnal changes in women's Tc using a body-heat-balance equation during thermal transient.
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Gordon CJ. The mouse thermoregulatory system: Its impact on translating biomedical data to humans. Physiol Behav 2017; 179:55-66. [PMID: 28533176 PMCID: PMC6196327 DOI: 10.1016/j.physbeh.2017.05.026] [Citation(s) in RCA: 145] [Impact Index Per Article: 20.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2017] [Revised: 05/04/2017] [Accepted: 05/18/2017] [Indexed: 01/01/2023]
Abstract
The laboratory mouse has become the predominant test species in biomedical research. The number of papers that translate or extrapolate data from mouse to human has grown exponentially since the year 2000. There are many physiological and anatomical factors to consider in the process of extrapolating data from one species to another. Body temperature is, of course, a critical determinant in extrapolation because it has a direct impact on metabolism, cardiovascular function, drug efficacy, pharmacokinetics of toxins and drugs, and many other effects. While most would consider the thermoregulatory system of mice to be sufficiently stable and predictable as to not be a cause for concern, the thermal physiology of mice does in fact present unique challenges to the biomedical researcher. A variable and unstable core temperature, high metabolic rate, preference for warm temperatures, large surface area: body mass ratio, and high rate of thermal conductance, are some of the key factors of mice that can affect the interpretation and translation of data to humans. It is the intent of this brief review to enlighten researchers studying interspecies translation of biomedical data on the salient facets of the mouse thermal physiology and show how extrapolation in fields such as physiology, psychology, nutrition, pharmacology, toxicology, and pathology.
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Affiliation(s)
- Christopher J Gordon
- Toxicity Assessment Division, National Health Effects and Environmental Research Laboratory, U.S. Environmental Protection Agency, Research Triangle Park, NC 27711, United States.
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Ciuha U, Mekjavic IB. Thermal comfort zone of the hands, feet and head in males and females. Physiol Behav 2017; 179:427-433. [DOI: 10.1016/j.physbeh.2017.07.020] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2017] [Revised: 06/15/2017] [Accepted: 07/13/2017] [Indexed: 11/25/2022]
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Morrison SA, Ciuha U, Zavec-Pavlinić D, Eiken O, Mekjavic IB. The effect of a Live-high Train-high exercise regimen on behavioural temperature regulation. Eur J Appl Physiol 2016; 117:255-265. [PMID: 28025662 DOI: 10.1007/s00421-016-3515-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2016] [Accepted: 12/08/2016] [Indexed: 11/28/2022]
Abstract
PURPOSE Acute hypoxia alters the threshold for sensation of cutaneous thermal stimuli. We hypothesised that hypoxia-induced alterations in cutaneous temperature sensation may lead to modulation of the perception of temperature, ultimately influencing behavioural thermoregulation and that the magnitude of this effect could be influenced by daily physical training. METHODS Fourteen men were confined 10 days to a normobaric hypoxic environment (PIO2 = 88.2 ± 0.6 mmHg, corresponding to 4175 m elevation). Subjects were randomly assigned to a non-exercising (Live-high, LH, N = 6), or exercising group (Live-high Train-high, LH-TH, N = 8) comprised of 1-h bouts of cycle ergometry, twice daily, at a work-rate equivalent to 50% hypoxic peak power output. A subset of subjects (N = 5) also completed a control trial under normoxic conditions. The thermal comfort zone (TCZ) was determined in normoxia, and during hypoxic confinement days 2 (HC2) and 10 (HC10) in both groups using a water-perfused suit in which water temperature was regulated by the subjects within a range, they deemed thermally comfortable. Mean skin temperature and proximal-distal temperature gradients (two sites: forearm-fingertip, calf-toe) were recorded each minute throughout the 60-min protocol. RESULTS The average width of the TCZ did not differ between the control group (9.0 ± 6.9 °C), and the LH and LH-TH groups on days HC2 (7.2 ± 4.2 °C) and HC10 (10.2 ± 7.5 °C) of the hypoxic exposure (p = 0.256). [Formula: see text] was marginally higher on HC2 (35.9 ± 1.0 °C) compared to control (34.9 ± 0.8 °C, p = 0.040), but not on HC10 (35.6 ± 1.0 °C), reflecting the responses of hand perfusion. CONCLUSION There was a little systematic effect of hypoxia or exercise training on TCZ magnitude or boundary temperatures.
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Affiliation(s)
- Shawnda A Morrison
- Department of Automation, Biocybernetics and Robotics, Jozef Stefan Institute, Jamova 39, SI-1000, Ljubljana, Slovenia. .,Faculty of Mathematics, Natural Sciences and Information Technology, University of Primorska, Titov trg 4, 6000, Koper, Slovenia.
| | - Urša Ciuha
- Department of Automation, Biocybernetics and Robotics, Jozef Stefan Institute, Jamova 39, SI-1000, Ljubljana, Slovenia
| | - Daniela Zavec-Pavlinić
- Faculty of Mechanical Engineering, University of Maribor, Smetanova ulica 17, 2000, Maribor, Slovenia
| | - Ola Eiken
- Department of Environmental Physiology, Swedish Aerospace Physiology Centre, Royal Institute of Technology, Berzelius v. 13, Stockholm, Sweden
| | - Igor B Mekjavic
- Department of Automation, Biocybernetics and Robotics, Jozef Stefan Institute, Jamova 39, SI-1000, Ljubljana, Slovenia.,Department of Biomedical Physiology and Kinesiology, Simon Fraser University, 8888 University Drive, Burnaby, BC, V5A 1S6, Canada
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