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- Keramidas, Michail E., et al.
(author)
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Hand temperature responses to local cooling after a 10-day confinement to normobaric hypoxia with and without exercise
- 2015
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In: Scandinavian Journal of Medicine and Science in Sports. - : John Wiley & Sons. - 0905-7188 .- 1600-0838. ; 25:5, s. 650-660
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Journal article (peer-reviewed)abstract
- The study examined the effects of a 10-day normobaric hypoxic confinement (FiO2: 0.14), with (HT; n = 8) or without (HA; n = 6) exercise, on the hand-temperature responses during and after local cold stress. Before and after the confinement, subjects immersed their right hand for 30 min in 8°C water (CWI), followed by a 15-min spontaneous rewarming (RW), while breathing either room air (AIR), or a hypoxic gas mixture (HYPO). The hand-temperature responses were monitored with thermocouples and infrared-thermography. The confinement did not influence the hand-temperature responses of the HA group during the AIR and HYPO CWI and the HYPO RW phases; but it impaired the AIR RW response (-1.3°C; P = 0.05). After the confinement, the hand-temperature responses were unaltered in the HT group throughout the AIR trial. However, the average hand-temperature was increased during the HYPO CWI (+0.5°C; P ≤ 0.05) and RW (+2.4°C; P ≤ 0.001) phases. Accordingly, present findings suggest that prolonged exposure to normobaric hypoxia per se does not alter the hand-temperature responses to local cooling; yet, it impairs the normoxic rewarming response. Conversely, the combined stimuli of continuous hypoxia and exercise enhance the finger cold-induced vasodilatation and hand-rewarming responses, specifically, under hypoxic conditions.
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| 2. |
- Keramidas, Michail E., Assistant Professor, et al.
(author)
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Short-term sleep deprivation and human thermoregulatory function during thermal challenges
- 2021
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In: Experimental Physiology. - : Wiley. - 0958-0670 .- 1469-445X. ; 106:5, s. 1139-1148
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Journal article (peer-reviewed)abstract
- bstractRelatively short periods of inadequate sleep provoke physiological and psychological perturbations, typically leading to functional impairments and degradation in performance. It is commonly accepted that sleep deprivation also disturbs thermal homeostasis, plausibly enhancing susceptibility to cold- and heat-related illnesses. Herein, we summarize the current state of human-based evidence on the impact of short-term (i.e., ≤4 nights) sleep deprivation on autonomic and behavioural thermoeffectors during acute exposure to low and high ambient temperatures. The purpose of this brief narrative review is to highlight knowledge gaps in the area and stimulate future research to investigate whether sleep deprivation constitutes a predisposing factor for the development of thermal injuries.
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| 5. |
- Keramidas, Michail E., et al.
(author)
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Enhancement of the finger cold-induced vasodilation response with exercise training
- 2010
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In: European Journal of Applied Physiology. - : Springer Science and Business Media LLC. - 1439-6319 .- 1439-6327. ; 109:1, s. 133-140
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Journal article (peer-reviewed)abstract
- Cold-induced vasodilatation (CIVD) is a cyclical increase in finger temperature that has been suggested to provide cryoprotective function during cold exposures. Physical fitness has been suggested as a potential factor that could affect CIVD response, possibly via central (increased cardiac output, decreased sympathetic nerve activity) and/or peripheral (increased microcirculation) cardiovascular and neural adaptations to exercise training. Therefore, the purpose of this study was to investigate the effect of endurance exercise training on the CIVD response. Eighteen healthy males trained 1 h d(-1) on a cycle ergometer at 50% of peak power output, 5 days week(-1) for 4-weeks. Pre, Mid, Post, and 10 days after the cessation of training and on separate days, subjects performed an incremental exercise test to exhaustion ((V) over dotO(2peak)); and a 30-min hand immersion in 8 degrees C water to examine their CIVD response. The exercise-training regimen significantly increased (V) over dotO(2peak) (Pre: 46.0 +/- 5.9, Mid: 52.5 +/- 5.7, Post: 52.1 +/- 6.2, After: 52.6 +/- 7.6 ml kg(-1) min-1; P < 0.001). There was a significant increase in average finger skin temperature (Pre: 11.9 +/- 2.4, After: 13.5 +/- 2.5 degrees C; P < 0.05), the number of waves (Pre: 1.1 +/- 1.0, After: 1.7 +/- 1.1; P < 0.001) and the thermal sensation (Pre: 1.7 +/- 0.9, After: 2.5 +/- 1.4; P < 0.001), after training. In conclusion, the aforementioned endurance exercise training significantly improved the finger CIVD response during cold-water hand immersion.
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| 8. |
- Keramidas, Michail E., et al.
(author)
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Respiratory muscle endurance training : Effect on normoxic and hypoxic exercise performance
- 2010
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In: European Journal of Applied Physiology. - : Springer Science and Business Media LLC. - 1439-6319 .- 1439-6327. ; 108:4, s. 759-769
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Journal article (peer-reviewed)abstract
- The aim of this study was to investigate the effect of respiratory muscle endurance training on endurance exercise performance in normoxic and hypoxic conditions. Eighteen healthy males were stratified for age and aerobic capacity; and randomly assigned either to the respiratory muscle endurance training (RMT = 9) or to the control training group (CON = 9). Both groups trained on a cycle-ergometer 1 h day(-1), 5 days per week for a period of 4 weeks at an intensity corresponding to 50% of peak power output. Additionally, the RMT group performed a 30-min specific endurance training of respiratory muscles (isocapnic hyperpnea) prior to the cycle ergometry. Pre, Mid, Post and 10 days after the end of training period, subjects conducted pulmonary function tests (PFTs), maximal aerobic tests in normoxia ((V) over dotO(2max)NOR), and in hypoxia ((V) over dotO(2max)HYPO; F(I)O(2) = 0.12); and constant-load tests at 80% of (V) over dotO(2max)NOR in normoxia (CLT(NOR)), and in hypoxia (CLT(HYPO)). Both groups enhanced (V) over dotO(2max)NOR (CON: +13.5%; RMT: +13.4%), but only the RMT group improved (V) over dotO(2max)HYPO Post training (CON: -6.5%; RMT: +14.2%). Post training, the CON group increased peak power output, whereas the RMT group had higher values of maximum ventilation. Both groups increased CLT(NOR) duration (CON: +79.9%; RMT: +116.6%), but only the RMT group maintained a significantly higher CLT(NOR) 10 days after training (CON: +56.7%; RMT: +91.3%). CLT(HYPO) remained unchanged in both groups. Therefore, the respiratory muscle endurance training combined with cycle ergometer training enhanced aerobic capacity in hypoxia above the control values, but did not in normoxia. Moreover, no additional effect was obtained during constant-load exercise.
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| 9. |
- Keramidas, Michail E., et al.
(author)
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Severe hypoxia during incremental exercise to exhaustion provokes negative post-exercise affects
- 2016
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In: Physiology and Behavior. - : Elsevier. - 0031-9384 .- 1873-507X. ; 156
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Journal article (peer-reviewed)abstract
- The post-exercise emotional response is mainly dependent on the intensity of the exercise performed; moderate exercise causes positive feelings, whereas maximal exercise may prompt negative affects. Acute hypoxia impairs peak O2 uptake (VO2peak), resulting in a shift to a lower absolute intensity at the point of exhaustion. Hence, the purpose of the study was to examine whether a severe hypoxic stimulus would influence the post-exercise affective state in healthy lowlanders performing an incremental exercise to exhaustion. Thirty-six male lowlanders performed, in a counter-balanced order and separated by a 48-h interval, two incremental exercise trials to exhaustion to determine their VO2peak, while they were breathing either room air (AIR; FiO2: 0.21), or a hypoxic gas mixture (HYPO; FiO2: 0.12). Before and immediately after each trial, subjects were requested to complete two questionnaires, based on how they felt at that particular moment: (i) the Profile of Mood States-Short Form, and (ii) the Activation Deactivation Adjective Check List. During the post-exercise phase, they also completed the Multidimensional Fatigue Inventory. VO2peak was significantly lower in the HYPO than the AIR trial (~15%; p<0.001). Still, after the HYPO trial, energy, calmness and motivation were markedly impaired, whereas tension, confusion, and perception of physical and general fatigue were exaggerated (p≤0.05). Accordingly, present findings suggest that an incremental exercise to exhaustion performed in severe hypoxia provokes negative post-exercise emotions, induces higher levels of perceived fatigue and decreases motivation; the affective responses coincide with the comparatively lower VO2peak than that achieved in normoxic conditions.
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