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Keramidas, Michail E., Assistant Professor, et al.
(författare)
Short-term sleep deprivation and human thermoregulatory function during thermal challenges
2021
Ingår i: Experimental Physiology. - : Wiley. - 0958-0670 .- 1469-445X. ; 106:5, s. 1139-1148
Tidskriftsartikel (refereegranskat) 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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Amon, M., et al.
(författare)
The effect of a sleep high-train low regimen on the finger cold-induced vasodilation response
2012
Ingår i: High Altitude Medicine & Biology. - : Mary Ann Liebert Inc. - 1527-0297 .- 1557-8682. ; 13:1, s. 32-39
Tidskriftsartikel (refereegranskat) abstract
The present study evaluated the effect of a sleep high-train low regimen on the finger cold-induced vasodilation (CIVD) response. Seventeen healthy males were assigned to either a control (CON; n=9) or experimental (EXP; n=8) group. Each group participated in a 28-day aerobic training program of daily 1-h exercise (50% of peak power output). During the training period, the EXP group slept at a simulated altitude of 2800 meters (week 1) to 3400 m (week 4) above sea level. Normoxic (CIVD(NOR); CON and EXP groups) and hypoxic (CIVD(HYPO); F(I)O(2)=0.12; EXP group only) CIVD characteristics were assessed before and after the training period during a 30-min immersion of the hand in 8°C water. After the intervention, the EXP group had increased average finger skin temperature (CIVD(NOR): +0.5°C; CIVD(HYPO): +0.5°C), number of waves (CIVD(NOR): +0.5; CIVD(HYPO): +0.6), and CIVD amplitude (CIVD(NOR): +1.5°C; CIVD(HYPO): +3°C) in both CIVD tests (p<0.05). In contrast, the CON group had an increase in only the CIVD amplitude (+0.5°C; p<0.05). Thus, the enhancement of aerobic performance combined with altitude acclimatization achieved with the sleep high-train low regimen contributed to an improved finger CIVD response during cold-water hand immersion in both normoxic and hypoxic conditions.
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Brink, Andreas, et al.
(författare)
Factors of significance for the ability of fighter pilots to visually indicate the magnitude of roll tilt during simulated turns in a centrifuge
2024
Ingår i: Perception. - : SAGE Publications. - 0301-0066 .- 1468-4233. ; 53:2, s. 75-92
Tidskriftsartikel (refereegranskat) abstract
During coordinated flight and centrifugation, pilots show interindividual variability in perceived roll tilt. The study explored how this variability is related to perceptual and cognitive functions. Twelve pilots underwent three 6-min centrifugations on two occasions (G levels: 1.1G, 1.8G, and 2.5G; gondola tilts: 25°, 56°, and 66°). The subjective visual horizontal (SVH) was measured with an adjustable luminous line and the pilots gave estimates of experienced G level. Afterward, they were interrogated regarding the relationship between G level and roll tilt and adjusted the line to numerically mentioned angles. Generally, the roll tilt during centrifugation was underestimated, and there was a large interindividual variability. Both knowledge on the relationship between G level and bank angle, and ability to adjust the line according to given angles contributed to the prediction of SVH in a multiple regression model. However, in most cases, SVH was substantial smaller than predictions based on specific abilities.
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Debevec, Tadej, et al.
(författare)
Acute short-term hyperoxia followed by mild hypoxia does not increase EPO production : resolving the "normobaric oxygen paradox''
2012
Ingår i: European Journal of Applied Physiology. - : Springer Science and Business Media LLC. - 1439-6319 .- 1439-6327. ; 112:3, s. 1059-1065
Tidskriftsartikel (refereegranskat) abstract
Recent findings suggest that besides renal tissue hypoxia, relative decrements in tissue oxygenation, using a transition of the breathing mixture from hyperoxic to normoxic, can also stimulate erythropoietin (EPO) production. To further clarify the importance of the relative change in tissue oxygenation on plasma EPO concentration [EPO], we investigated the effect of a consecutive hyperoxic and hypoxic breathing intervention. Eighteen healthy male subjects were assigned to either IHH (N = 10) or CON (N = 8) group. The IHH group breathed pure oxygen (F(i)O(2) ~ 1.0) for 1 h, followed by a 1-h period of breathing a hypoxic gas mixture (F(i)O(2) ~ 0.15). The CON group breathed a normoxic gas mixture (F(i)O(2) ~ 0.21) for the same duration (2 h). Blood samples were taken just before, after 60 min, and immediately after the 2-h exposure period. Thereafter, samples were taken at 3, 5, 8, 24, 32, and 48 h after the exposure. During the breathing interventions, subjects remained in supine position. There were significant increases in absolute [EPO] within groups at 8 and 32 h in the CON and at 32 h only in the IHH group. No significant differences in absolute [EPO] were observed between groups following the intervention. Relative (∆[EPO]) levels were significantly lower in the IHH than in the CON group, 5 and 8 h following exposure. The tested protocol of consecutive hyperoxic-hypoxic gas mixture breathing did not induce [EPO] synthesis stimulation. Moreover, the transient attenuation in ∆[EPO] in the IHH group was most likely due to a hyperoxic suppression. Hence, our findings provide further evidence against the "normobaric O(2) paradox" theory.
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Debevec, T, et al.
(författare)
Hematological responses to two different intermittent hypoxic training regimens
2009
Konferensbidrag (refereegranskat) abstract
"Hypoxic training has been reported to enhance athletes’ altitude and sea-level performance by augmenting oxygen carrying capacity of the blood, as a consequence of increases in hematocrit and hemoglobin concentrations. However the effect of intermittent hypoxic training on hematological responses remains unresolved."This study investigated the effect of two intermittent hypoxic training regimens on the response of hematological indices. Healthy male Ss (N = 27) were equally assigned to a control group, a live low-train high (LL-TH) group, or a intermittent hypoxic exposure group. Ss performed a one-hour submaximal endurance exercise on a cycle ergometer, five days per week for four weeks, at an intensity corresponding to 50% of normoxic peak power output for the control and intermittent hypoxic exposure groups, and to 50% of hypoxic peak power output for the LL-TH group. Thus, all groups trained at the same relative work rate. The absolute work rate during training was 18-20 W lower for the LL-TH group compared to the other two groups. All groups lived at an altitude of ~300 m above sea level. The control and intermittent hypoxic exposure groups also trained at this altitude, whereas the LL-TH group trained in a hypoxic chamber, breathing a hypoxic mixture (FIO2=12%). In addition to the daily exercise training, the intermittent hypoxic exposure group also inspired a hypoxic gas mixture at rest, and prior to the cycle ergometry. The intermittent hypoxic training comprised breathing a hypoxic mixture during seven phases. Each phase consisted of five minutes of breathing a hypoxic mixture, followed by three minutes of breathing a normoxic gas mixture. Prior to, during, at the end, and 10 days after the training period, blood samples were taken from all Ss in order to measure hemoglobin, hematocrit, erythrocytes, ferritin, and transferrin concentrations.No significant differences were observed between groups in any measured hematological variables. Similarly, no significant differences were found within groups at the different testing periods.Implication. Although it has been reported that both LL-TH and intermittent hypoxic exposure protocols provide hematological benefits, that was not confirmed by this study. The tested protocols did not induce any changes in the measured hematological variables; therefore no improvements of the oxygen carrying capacity of the blood should be expected following this type of hypoxic training.
