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  • 101. McDonnell, A.C.
    et al.
    Golemis, A
    Eiken, Ola
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology. KTH, School of Technology and Health (STH), Centres, Swedish Aerospace Physiology Centre, SAPC.
    Mekjavic, I.B.
    PlanHab: Comparison of the circadian rythm of proximal-distal temperature gradient observed during exposures to normobaric and hypobaric hypoxia2014Conference paper (Refereed)
  • 102. McDonnell, AC
    et al.
    Stavrou, N
    Eiken, Ola
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology. KTH, School of Technology and Health (STH), Centres, Swedish Aerospace Physiology Centre, SAPC.
    Mekjavic, IB
    The Effect of a Live-High/Train-High Regimen on Emotional State2015Conference paper (Refereed)
  • 103. Mekjavic, I. B.
    et al.
    McDonnell, A. C.
    Keramidas, Michail E.
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Kolegard, Roger
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Lind, Britta
    KTH, School of Technology and Health (STH), Medical Engineering, Medical Imaging.
    Eiken, Ola
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Lunar habitat simulation2013Conference paper (Other academic)
  • 104. Mekjavic, IB
    et al.
    Bali, T
    McDonnell, AC
    Debevec, T
    Simpson, EJ
    MacDonald, IA
    Eiken, Ola
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology. KTH, School of Technology and Health (STH), Centres, Swedish Aerospace Physiology Centre, SAPC.
    FemHab: Effects of 10-day planetary habitation simulation on body composition and resting energy expenditure in females2015Conference paper (Refereed)
  • 105. Mekjavic, I.B.
    et al.
    Ciuha, U
    Grönkvist, Mikael
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Eiken, Ola
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    The physiological strain index does not predict heat exhaustion2014Conference paper (Refereed)
  • 106. Mekjavic, I.B.
    et al.
    Dolenc-Groselj, L
    Morrison, S.A.
    Mirnik, D
    Korsic, S
    Eiken, Ola
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology. KTH, School of Technology and Health (STH), Centres, Swedish Aerospace Physiology Centre, SAPC.
    PlanHab: Sleep and respiration during 21-day hypoxic bedrest2014Conference paper (Refereed)
  • 107. Mekjavic, IB
    et al.
    MacDonald, IA
    Chouker, A
    Rittweger, J
    Grassi, B
    Aliverti, A
    Biolo, G
    Eiken, Ola
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology. KTH, School of Technology and Health (STH), Centres, Swedish Aerospace Physiology Centre, SAPC.
    The Planetary Habitat project2015Conference paper (Refereed)
  • 108. Mekjavic, I.B.
    et al.
    McDonnel, A
    Eiken, Ola
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology. KTH, School of Technology and Health (STH), Centres, Swedish Aerospace Physiology Centre, SAPC.
    PlanHab: Circadian rythm of proximal-distal temperature gradient during 21-day hypoxic bedrest2014Conference paper (Refereed)
  • 109. Mekjavic, I.B.
    et al.
    Pattyn, N
    Mairesse, O
    Cortoos, A
    Collet, G
    Fernandez, H.T.
    MacDonald-Nethercott, E
    Morrison, S.A.
    Dolenc-Groselj, L
    Eiken, Ola
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology. KTH, School of Technology and Health (STH), Centres, Swedish Aerospace Physiology Centre, SAPC.
    Sleep and performance during the winter months in Antarctica2014Conference paper (Refereed)
  • 110. Mekjavic, Igor B.
    et al.
    Amon, Mojca
    Kölegård, Roger
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Kounalakis, Stylianos N.
    Simpson, Liz
    Eiken, Ola
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Keramidas, Michail E.
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    MacDonald, IanA.
    The effect of normobaric hypoxic confinement on metabolism, gut hormones and body composition2016In: Frontiers in Physiology, ISSN 1664-042X, E-ISSN 1664-042X, Vol. 7, no 202Article in journal (Refereed)
  • 111. Morrison, S. A.
    et al.
    Mirnik, D.
    Korsic, S.
    Eiken, Ola
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Mekjavic, I. B.
    Groselj, L. Dolenc
    Planetary habitat simulation: interactions between bedrest, hypoxia and confinement on sleep and breathing2014In: Journal of Sleep Research, ISSN 0962-1105, E-ISSN 1365-2869, Vol. 23, p. 196-196Article in journal (Other academic)
  • 112. Morrison, S
    et al.
    Pangerc, A
    Eiken, Ola
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Mekjavic, IB
    Dolenc, L
    Effect of exercise on night periodic breathing and loop gain during hypoxic confinement2016In: Respirology (Carlton South. Print), ISSN 1323-7799, E-ISSN 1440-1843, Vol. 21, no 4, p. 746-753Article in journal (Refereed)
  • 113. Morrison, SA
    et al.
    Cihua, U
    Zavec-Pavlinic, D
    Eiken, Ola
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Mekjavic, IB
    The effect of a Live-high Train-high exercise regimen on behavioural temperature regulation2017In: European Journal of Applied Physiology, ISSN 1439-6319, E-ISSN 1439-6327, Vol. 117, p. 255-265, article id 28025662Article in journal (Refereed)
    Abstract [en]

    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.

  • 114. Morrison, Shawnda A
    et al.
    Gorjanc, Jurij
    Eiken, Ola
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Mekjavic, Igor B
    Finger and Toe Temperature Responses to Cold After Freezing Cold Injury in Elite Alpinists.2015In: Wilderness & environmental medicine, ISSN 1545-1534, Vol. 26, no 3Article in journal (Refereed)
    Abstract [en]

    OBJECTIVE: To assess whether previous freezing cold injuries (FCI) would affect digit skin temperatures and rewarming rates during a follow-up cold stress test protocol.; DESIGN: Nonrandomized control trial.; METHODS: Twenty elite alpinists participated; alpinists with previous FCI requiring digit amputations (injured, INJ: n = 10 total, n = 8 male) were compared with ability-matched, uninjured alpinists (control, CON: n = 10, all male). Digit skin temperature was measured using infrared thermography as an index of peripheral digit perfusion after a cold stress test, which consisted of 30 minutes of immersion in 8°C water.; RESULTS: The INJ alpinists' injured toes were warmer (approximately 6%) than their uninjured toes immediately after cold immersion (95% CI, 0.01°C to 1.00°C; P = .05); there were no differences between the rates of rewarming of injured and uninjured toes (INJ, 0.5° ± 0.1°C/min; CON, 0.7° ± 0.3°C/min; P = .16). Although the INJ alpinists had colder injured fingers immediately after the 35°C warm bath compared with their own uninjured fingers (32.2° ± 2.0°C vs 34.5° ± 0.5°C; P = .02), there were no differences observed between the rates of rewarming of injured and uninjured fingers after cold exposure (INJ, 1.1° ± 0.2°C/min; CON, 1.3° ± 0.5°C/min; P = .22).; CONCLUSIONS: Even after FCI that requires digit amputation, there is no evidence of different tissue rates of rewarming between the injured and uninjured fingers or toes of elite alpinists.

  • 115.
    Norrbrand, Lena
    et al.
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Grönkvist, Mikael
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Johannesson, Björn
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Eiken, Ola
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Extensive increase of metabolic demand while walking wearing night vision goggles in hilly terrain2017In: Journal of Science and Medicine in Sport, ISSN 1440-2440, E-ISSN 1878-1861, Vol. 20, article id S77Article in journal (Refereed)
    Abstract [en]

    Introduction: The motivation for the foot-borne soldiers to carry out nighttime operations may be to reduce heat strain. We have previously found elevated metabolic demand (+7 %), and hence endogenous heat production, during walking on a flat gravel road in darkness wearing Night Vision Goggles (NVG) compared with wearing a headlamp. The aim of the present study was to evaluate the effect of wearing NVG while walking in a hilly forest terrain, and compare results between skilled and unskilled NVG users.

    Methods: A group of cadets, i.e. unskilled (5 men, 6 women, age: 23±3 yrs, height: 172±10 cm, weight: 75±12 kg) and skilled NVG users (9 men, age: 26±2 yrs, height: 184±6 cm, weight: 84±5 kg) participated. At night time, subjects walked 1.1 km at a self-selected comfortable pace in a hilly forest, following a trail in the uphill part, and walking on the under bush in the downhill part. Walks were performed wearing either a headlamp (Light), monocular NVG (MNVG), binocular NVG (BNVG), or MNVG and 25 kg extra weight (backpack and body armor). Oxygen uptake, heart rate, rate of perceived exertion and walking speed were measured. To evaluate walking economy, oxygen uptake was expressed in relation to body mass and distance covered (VO2 mL·kg-1·km-1). 

    Results: In both groups, VO2 (mL·kg-1·km-1) was higher in all three conditions with limited vision (MNVG; BNVG; Backpack) than in the Light condition, both during the Uphill (MNVG/BNVG; skilled: +25/+24%, unskilled: +35/+28%) and Downhill part (MNVG/BNVG; skilled: +42/+44%, unskilled: +67/+51%). In the Backpack condition, the inter-group difference in mechanical efficiency was maintained or exaggerated: Uphill (skilled: +46%, unskilled: +80%), Downhill (skilled: +70%, unskilled: +115%). The skilled NVG users walked faster, but there was no difference in heart rate between groups. In the unskilled, heart rate was higher in the MNVG and BNVG than in the Light condition during the Downhill part. Likewise, in the unskilled, the rate of perceived exertion was higher in the MNVG and BNVG than in the Light condition. 

    Conclusions: Despite that in darkness foveal vision is markedly improved by NVG, it appears that the mechanical efficiency during walking in hilly terrain is markedly lower whilst wearing NVG than with full vision, regardless of whether the soldier is a skilled or unskilled NVG user.

  • 116.
    Norrbrand, Lena
    et al.
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Grönkvist, Mikael
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Johannesson, Björn
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Rappe, A
    Sjölin, J
    Eiken, Ola
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Metabolic demand during walking with night vision goggles2014Conference paper (Refereed)
  • 117.
    Norrbrand, Lena
    et al.
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Grönkvist, Mikael
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Johannesson, Björn
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Rappe, Annika
    Sjölin, Johan
    Eiken, Ola
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Walking with night vision goggles increases metabolic demand2014Conference paper (Refereed)
  • 118.
    Norrbrand, Lena
    et al.
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Kölegård, Roger
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Keramidas, Michail E.
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Eiken, Ola
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Mekjavic, Igor B.
    No association between hand and foot temperature responses during local cold stress and rewarming.2017In: European Journal of Applied Physiology, ISSN 1439-6319, E-ISSN 1439-6327, Vol. 117, no 6, p. 1141-1153Article in journal (Refereed)
    Abstract [en]

    PURPOSE: The purpose was to examine whether associations exist between temperature responses in the fingers vs. toes and hand vs. foot during local cold-water immersion and rewarming phases.

    METHODS: Seventy healthy subjects (58 males, 12 females) immersed their right hand or right foot, respectively, in 8 °C water for 30 min (CWI phase), followed by a 15-min spontaneous rewarming (RW) in 25 °C air temperature.

    RESULTS: Temperature was lower in the toes than the fingers during the baseline phase (27.8 ± 3.0 vs. 33.9 ± 2.5 °C, p < 0.001), parts of the CWI phase (min 20-30: 8.8 ± 0.7 vs. 9.7 ± 1.4 °C, p < 0.001), and during the RW phase (peak temperature: 22.5 ± 5.1 vs. 32.7 ± 3.6 °C, p < 0.001). Cold-induced vasodilatation (CIVD) was more common in the fingers than in the toes (p < 0.001). Within the first 10 min of CWI, 61% of the subjects exhibited a CIVD response in the fingers, while only 6% of the subjects had a CIVD response in the toes. There was a large variability of temperature responses both within and between extremities, and there was a weak correlation between finger- and toe temperature both during the CWI (r = 0.21, p = 0.08) and the RW phases (r = 0.26, p = 0.03).

    CONCLUSIONS: Results suggest that there is generally a lower temperature in the toes than the fingers after a short time of local cold exposure and that the thermal responses of the fingers/hands are not readily transferable to the toes/foot.

  • 119. Petrič, M
    et al.
    Jakovljević, M
    Eiken, Ola
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology. KTH, School of Technology and Health (STH), Centres, Swedish Aerospace Physiology Centre, SAPC.
    Mekjavic, IB
    FemHab: Effect of 10-day hypoxic bed rest on static balance in females2015Conference paper (Refereed)
  • 120. Potrc, M
    et al.
    Šuštar, M
    Jaki Mekjavic, P
    Hawlina, M
    Eiken, Ola
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology. KTH, School of Technology and Health (STH), Centres, Swedish Aerospace Physiology Centre, SAPC.
    Mekjavic, IB
    FemHab: The effect of sustained bedrest and hypoxia on electroretinographic responses2015Conference paper (Refereed)
  • 121. Režen, T.
    et al.
    Kovanda, A.
    Eiken, Ola
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology. KTH, School of Technology and Health (STH), Centres, Swedish Aerospace Physiology Centre, SAPC.
    Mekjavic, I.B.
    Rogelj, B.
    Expression changes in human skeletal muscle miRNAs following 10 days of bed rest in young healthy males2014In: Acta Physiologica, ISSN 1748-1708, E-ISSN 1748-1716, Vol. 210, no 3, p. 655-666Article in journal (Refereed)
    Abstract [en]

    Aim: Studies in humans show global changes in mRNA and protein expression occur in human skeletal muscle during bed rest. As microRNAs are important regulators of expression, we analysed the global microRNA expression changes in human muscle following 10 days of sustained bed rest, with the rationale that miRNAs play key roles in atrophy of skeletal muscle. Methods: We analysed expression of miRNA and selected target proteins before and after 10 days of bed rest in biopsies obtained from the vastus lateralis muscle of 6 healthy males. Results: Fifteen of 152 miRNAs detected in human muscle tissue were differentially expressed, and all of them with exception of two were downregulated. The downregulated miRNAs include the following: miR-206, a myomir involved in function and maintenance of skeletal muscle; miR-23a, involved in insulin response and atrophy defence; and several members of the let-7 family involved in cell cycle, cell differentiation and glucose homeostasis. Predicted gene targets of these miRNAs are members of the MAPK, TNF receptor, ALK1, TGF-beta receptor and SMAD signalling pathways. All of these pathways were previously indicated to be involved in skeletal muscle response to physical inactivity. We also measured protein expression of selected miRNA targets and observed a decrease in HDAC4. Conclusion: Our data demonstrate that miRNAs in postural muscles are affected by sustained inactivity and unloading, as induced by prolonged bed rest, and hence are potentially involved in regulation of skeletal muscle adjustments to inactivity. We also propose new miRNAs involved in regulation of biological processes in adult human muscle.

  • 122. Režen, T.
    et al.
    Kovanda, A.
    Eiken, Ola
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Mekjavič, I.
    Rogelj, B.
    Response to the letter to the editor by Kristensen MM, Helge JW and Dela F2015In: Acta Physiologica, ISSN 1748-1708, E-ISSN 1748-1716, Vol. 215, no 2, p. 76-78Article in journal (Refereed)
  • 123. Rittweger, Joern
    et al.
    Debevec, Tadej
    Frings-Meuthen, Petra
    Lau, Patrick
    Mittag, Uwe
    Ganse, Bergita
    Ferstl, Philip G.
    Simpson, Elizabeth J.
    Macdonald, Ian A.
    Eiken, Ola
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Mekjavic, Igor B.
    On the combined effects of normobaric hypoxia and bed rest upon bone and mineral metabolism: Results from the PlanHab study2016In: Bone, ISSN 8756-3282, E-ISSN 1873-2763, Vol. 91, p. 130-138Article in journal (Refereed)
    Abstract [en]

    Bone losses are common as a consequence of unloading and also in patients with chronic obstructive pulmonary disease (COPD). Although hypoxia has been implicated as an important factor to drive bone loss, its interaction with unloading remains unresolved. The objective therefore was to assess whether human bone loss caused by unloading could be aggravated by chronic hypoxia. In a cross-over designed study, 14 healthy young men underwent 21-day interventions of bed rest in normoxia (NBR), bed rest in hypoxia (HBR), and hypoxic ambulatory confinement (HAmb). Hypoxic conditions were equivalent to 4000 m altitude. Bone metabolism (NTX, P1NP, sclerostin, DKK1) and phospho-calcic homeostasis (calcium and phosphate serum levels and urinary excretion, PTH) were assessed from regular blood samples and 24-hour urine collections, and tibia and femur bone mineral content was assessed by peripheral quantitative computed tomography (pQCT). Urinary NTX excretion increased (P<0.001) to a similar extent in NBR and HBR (P = 0.69) and P1NP serum levels decreased (P = 0.0035) with likewise no difference between NBR and HBR (P = 0.88). Serum total calcium was increased during bed rest by 0.059 (day D05, SE 0.05 mM) to 0.091 mM (day D21, P < 0.001), with no additional effect by hypoxia during bed rest (P = 0.199). HAmb led, at least temporally, to increased total serum calcium, to reduced serum phosphate, and to reduced phosphate and calcium excretion. In conclusion, hypoxia did not aggravate bed rest-induced bone resorption, but led to changes in phospho-calcic homeostasis likely caused by hyperventilation. Whether hyperventilation could have mitigated the effects of hypoxia in this study remains to be established.

  • 124. Rojc, Bojan
    et al.
    Morrison, Shawnda A.
    Eiken, Ola
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Mekjavic, Igor B.
    Dolenc-Groselj, Leja
    The separate and combined effects of hypoxia and sustained recumbency/inactivity on sleep architecture2014In: European Journal of Applied Physiology, ISSN 1439-6319, E-ISSN 1439-6327, Vol. 114, no 9, p. 1973-1981Article in journal (Refereed)
    Abstract [en]

    The objective was to determine the separate and combined effects of hypoxia and inactivity/unloading on sleep architecture during a 10-day period of confinement. Ten subjects participated in three 10-day trials in random order: hypoxic ambulatory (HAMB), hypoxic bedrest (HBR), and normoxic bedrest (NBR). During the HAMB and HBR trials, subjects were confined to a hypoxic facility. The hypoxia profile was: simulated altitude of 2,990 m on day 1, 3,380 m on day 2, and 3,881 m on day 3. In the NBR and HBR trials, subjects maintained a horizontal position throughout the confinement period. During each trial, sleep polysomnography was conducted one night prior to (baseline; altitude of facility is 940 m) and on the first (NT1, altitude 2,990 m) and tenth (NT10, altitude 3,881 m) night of the 10-day intervention. Average time in sleep stage 1 decreased from NT1 to NT10 irrespective of trial. Overall incidence and time spent in periodic breathing increased from NT1 to NT10 in both HAMB and HBR. During NT1, both HAMB and HBR reduced slow-wave sleep and increased light sleep, whereas NBR and HBR increased the number of awakenings/night. There were fewer awakenings during HAMB than NBR. Acute exposure to both hypoxia and bedrest (HBR) results in greater sleep fragmentation due to more awakenings attributed to bedrest, and lighter sleep as a result of reduced slow wave sleep caused by the hypoxic environment.

  • 125. Rullman, E
    et al.
    Mekjavic, IB
    Fischer, H
    Eiken, Ola
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    PlanHab (Planetary Habitat Simulation): the combined and separate effects of 21 days bed rest and hypoxic confinement on human skeletal muscle miRNA expression.2016In: Physiological Reports, E-ISSN 2051-817X, Vol. 4, no 8Article in journal (Refereed)
  • 126. Salvadego, D.
    et al.
    Keramidas, Michail E.
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Domenis, R.
    Mavelli, I.
    Eiken, Ola
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Mekjavic, I.B.
    Grassi, B.
    Site of impairment of oxidative function after 10- day normoxic or hypoxic bed rests2012Conference paper (Refereed)
  • 127. Salvadego, D
    et al.
    Keramidas, Michail E.
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Domenis, R
    Mavelli, I
    Mekjavic, I.B.
    Eiken, Ola
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Grassi, B
    Skeletal muscle oxidative function after a 10-day exposure to hypoxia and microgravity2013Conference paper (Refereed)
    Abstract [en]

    Skeletal muscle oxidative function was evaluated before (CTRL) and after 10 days of normobaric hypoxic (inspired PO2 12.5kPa) bed rest (H-BR) and normoxic bed rest (BR) in nine healthy young men (age: 24.1±1.7 years [mean±SD]). H-BR was taken as a simulation of lunar habitats. Pulmonary gas exchange and vastus lateralis muscle fractional O2-extraction (by near-infrared spectroscopy) were determined during an incremental cycle ergometer (CE) and one-leg knee extension (KE) exercise up to volitional exhaustion. Mitochondrial respiration was evaluated by high-resolution respirometry in permeabilized vastus lateralis fibers. During CE, peak pulmonary O2-uptake ( VO 2peak) significantly decreased by ~7 and 9 % after BR and

    H-BR, respectively. During KE, V O 2peak decreased significantly (by ~6%) after BR (0.83±0.07 vs. 0.89±0.08 [CTRL] L·min-1), but not after H-BR (0.86±0.07 vs. 0.90±0.07). Skeletal muscle peak fractional O2-extraction was significantly lower after BR (60±12 vs. 70±11% [CTRL]), but not after H-BR (65±12 vs. 71±10). No significant changes were observed in maximal ADP-stimulated mitochondrial respiration either after BR (48.9±11.5pmolO2·s-1·mg-1 wet weight) or H-BR (42.8±7.8) vs. CTRL (46.6±6.6). After relieving, by the KE exercise protocol, constraints related to cardiovascular O2-delivery, oxidative function in vivo was still impaired after BR, while a less pronounced impairment was evident after H-BR. Mitochondrial respiratory function ex-vivo was unchanged after both conditions. Peripheral O2-diffusion constraints and/or an impaired O2-delivery/O2-utilization coupling might be the main bottleneck to oxidative function in vivo after BR. Hypoxia may attenuate the impairment of muscle oxidative function observed after BR. 

  • 128. Salvadego, Desy
    et al.
    Keramidas, Michail E.
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Brocca, Lorenza
    Domenis, Rossana
    Mavelli, Irene
    Rittweger, Jörn
    Eiken, Ola
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Mekjavic, Igor B.
    Grassi, Bruno
    LunHab: Separate and combined effects of a 10-d exposure to hypoxia and inactivity on oxidative function in vivo and mitochondrial respiration ex vivo in humans.2016In: Journal of applied physiology, ISSN 8750-7587, E-ISSN 1522-1601, Vol. 121, no 1Article in journal (Refereed)
    Abstract [en]

    An integrative evaluation of oxidative metabolism was carried out in 9 healthy young men (age, 24.1 +/- 1.7 yr mean +/- SD) before (CTRL) and after a 10-day horizontal bed rest carried out in normoxia (N-BR) or hypoxia (H-BR, FIO2 = 0.147). H-BR was designed to simulate planetary habitats. Pulmonary O-2 uptake ((V) over dotO(2)) and vastus lateralis fractional O-2 extraction (changes in deoxygenated hemoglobin + myoglobin concentration, Delta[deoxy(Hb + Mb)] evaluated using near-infrared spectroscopy) were evaluated in normoxia and during an incremental cycle ergometer (CE) and one-leg knee extension (KE) exercise (aimed at reducing cardiovascular constraints to oxidative function). Mitochondrial respiration was evaluated ex vivo by high-resolution respirometry in permeabilized vastus lateralis fibers. During CE (V) over dotO(2peak) and Delta[deoxy(Hb + Mb)] peak were lower (P < 0.05) after both N-BR and H-BR than during CTRL; during KE the variables were lower after N-BR but not after H-BR. During CE the overshoot of Delta[deoxy(Hb + Mb)] during constant work rate exercise was greater in N-BR and H-BR than CTRL, whereas during KE a significant difference vs. CTRL was observed only after N-BR. Maximal mitochondrial respiration determined ex vivo was not affected by either intervention. In N-BR, a significant impairment of oxidative metabolism occurred downstream of central cardiovascular O-2 delivery and upstream of mitochondrial function, possibly at the level of the intramuscular matching between O-2 supply and utilization and peripheral O-2 diffusion. Superposition of hypoxia on bed rest did not aggravate, and partially reversed, the impairment of muscle oxidative function in vivo induced by bed rest. The effects of longer exposures will have to be determined.

  • 129. Salvadego, Desy
    et al.
    Keramidas, Michail E.
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology. KTH, School of Technology and Health (STH), Centres, Swedish Aerospace Physiology Centre, SAPC.
    Domenis, Rossana
    Kölegård, Roger
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology. KTH, School of Technology and Health (STH), Centres, Swedish Aerospace Physiology Centre, SAPC.
    Mavelli, Irene
    Rittweger, Jorn
    Eiken, Ola
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology. KTH, School of Technology and Health (STH), Centres, Swedish Aerospace Physiology Centre, SAPC.
    Mekjavic, Igor B.
    Grassi, Bruno
    PlanHab: responses of skeletal muscle oxidative function to bed rest and hypoxia2015Conference paper (Refereed)
  • 130. Salvadego, Desy
    et al.
    Keramidas, Michail E.
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Domenis, Rossana
    Mavelli, Irene
    Eiken, Ola
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Mekjavic, Igor B.
    Grassi, Bruno
    Effects of Hypoxia and Microgravity on Mitochondrial Respiration and Skeletal Muscle Oxidative Function2014In: Medicine & Science in Sports & Exercise, ISSN 0195-9131, E-ISSN 1530-0315, Vol. 46, no 5, p. 297-298Article in journal (Other academic)
  • 131. Salvadego, Desy
    et al.
    Keramidas, Michail E.
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Kölegård, Roger
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Mavelli, Irene
    Eiken, Ola
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Mekjavic, Igor B.
    Grassi, Bruno
    Prolonged exposure to hypoxia and microgravity: effects on skeletal muscle oxidative metabolism2015Conference paper (Refereed)
  • 132.
    Siebenmann, C
    et al.
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology. University of Zürich, Switzerland.
    Cathomen, A
    Hug, M
    Keiser, S
    Lundby, AK
    Hilty, MP
    Goetze, JP
    Rasmussen, P
    Lundby, C
    Hemoglobin mass and intravascular volume kinetics during and after exposure to 3,454 m altitude.2015In: Journal of applied physiology, ISSN 8750-7587, E-ISSN 1522-1601, Vol. 119, no 10Article in journal (Refereed)
    Abstract [en]

    High altitude (HA) exposure facilitates a rapid contraction of plasma volume (PV) and a slower occurring expansion of hemoglobin mass (Hbmass). The kinetics of the Hbmass expansion has never been examined by multiple repeated measurements and this was our primary study aim. The second aim was to investigate the mechanisms mediating the PV contraction. Nine healthy, normally-trained sea-level (SL) residents (8 males, 1 female) sojourned for 28 days at 3,454 m. Hbmass was measured and PV estimated by carbon monoxide re-breathing at SL, on every fourth day at HA, and one and two weeks upon return to SL. Four weeks at HA increased Hbmass by 5.26 % (range 2.5 - 11.1 %; p<0.001). The individual Hbmass increases commenced with up to 12 days delay and reached a maximal rate of 4.04 ± 1.02 g.d-1 after 14.9 ± 5.2 days. The probability for Hbmass to plateau increased steeply after 20-24 days. Upon return to SL Hbmass decayed by -2.46 ± 2.3 g.d-1, reaching values similar to baseline after two weeks. PV, aldosterone concentration and renin activity were reduced at HA (p<0.001) while the total circulating protein mass remained unaffected. In summary the Hbmass response to HA exposure followed a sigmoidal pattern with a delayed onset and a plateau after ~3 weeks. The decay rate of Hbmass upon descent to SL did not indicate major changes in the rate of erythrolysis. Moreover, our data supports that PV contraction at HA is regulated by the renin-angiotensin-aldosterone axis and not by changes in oncotic pressure.

  • 133.
    Siebenmann, Christoph
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Hemoglobin Mass Expansion during 13 d of Altitude Training: Altitude or Training?2016In: Medicine & Science in Sports & Exercise, ISSN 0195-9131, E-ISSN 1530-0315, Vol. 48, no 7, p. 1425-1425Article in journal (Refereed)
  • 134.
    Siebenmann, Christoph
    et al.
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Keramidas, Michail E.
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Rundqvist, Helene
    Mijwel, Sara
    Cowburn, Andrew
    Johnson, Randall
    Eiken, Ola
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Cutaneous exposure to hypoxia does not affect skin perfusion in humans2017In: Acta Physiologica, ISSN 1748-1708, E-ISSN 1748-1716, Vol. 220, no 3, p. 361-369Article in journal (Refereed)
    Abstract [en]

    Aim: Experiments have indicated that skin perfusion in mice is sensitive to reductions in environmental O-2 availability. Specifically, a reduction in skin-surface PO2 attenuates transcutaneous O-2 diffusion, and hence epidermal O-2 supply. In response, epidermal HIF-1 alpha expression increases and facilitates initial cutaneous vasoconstriction and subsequent nitric oxide-dependent vasodilation. Here, we investigated whether the same mechanism exists in humans. Methods: In a first experiment, eight males rested twice for 8 h in a hypobaric chamber. Once, barometric pressure was reduced by 50%, while systemic oxygenation was preserved by O-2-enriched (42%) breathing gas (Hypoxia(Skin)), and once barometric pressure and inspired O-2 fraction were normal (Control(1)). In a second experiment, nine males rested for 8 h with both forearms wrapped in plastic bags. O-2 was expelled from one bag by nitrogen flushing (Anoxia(Skin)), whereas the other bag was flushed with air (Control(2)). In both experiments, skin blood flux was assessed by laser Doppler on the dorsal forearm, and HIF-1 alpha expression was determined by immunohistochemical staining in forearm skin biopsies. Results: Skin blood flux during Hypoxia(Skin) and Anoxia(Skin) remained similar to the corresponding Control trial (P = 0.67 and P = 0.81). Immunohistochemically stained epidermal HIF-1 alpha was detected on 8.2 +/- 6.1 and 5.3 +/- 5.7% of the analysed area during Hypoxia(Skin) and Control(1) (P = 0.30) and on 2.3 +/- 1.8 and 2.4 +/- 1.8% during Anoxia(Skin) and Control(2) (P = 0.90) respectively. Conclusion: Reductions in skin-surface PO2 do not affect skin perfusion in humans. The unchanged epidermal HIF-1 alpha expression suggests that epidermal O-2 homoeostasis was not disturbed by Hypoxia(Skin)/Anoxia(Skin), potentially due to compensatory increases in arterial O-2 extraction.

  • 135.
    Siebenmann, Christoph
    et al.
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Lundby, Carsten
    Regulation of cardiac output in hypoxia.2015In: Scandinavian Journal of Medicine and Science in Sports, ISSN 0905-7188, E-ISSN 1600-0838, Vol. 25, no Suppl 4, p. 53-59Article in journal (Refereed)
    Abstract [en]

    This brief review addresses the regulation of cardiac output (Q) at rest and during submaximal exercise in acute and chronic hypoxia. To preserve systemic O-2 delivery in acute hypoxia Q is increased by an acceleration of heart rate, whereas stroke volume (SV) remains unchanged. Tachycardia is governed by activation of carotid and aortic chemoreceptors and a concomitant reduction in arterial baroreflex activation, all balancing sympathovagal activity toward sympathetic dominance. As hypoxia extends over several days a combination of different adaptive processes restores arterial O-2 content to or beyond sea level values and hence Q normalizes. The latter however occurs as a consequence of a decrease in SV whereas tachycardia persists. The diminished SV reflects a lower left ventricular end-diastolic volume which is primarily related to hypoxia-generated reduction in plasma volume. Hypoxic pulmonary vasoconstriction may contribute by increasing right ventricular afterload and thus decreasing its ejection fraction. In summary, the Q response to hypoxia is the result of a complex interplay between several physiological mechanisms. Future studies are encouraged to establish the individual contributions of the different components from an integrative perspective.

  • 136.
    Siebenmann, Christoph
    et al.
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Rasmussen, P.
    Does cerebral hypoxia facilitate central fatigue?2016In: Experimental Physiology, ISSN 0958-0670, E-ISSN 1469-445X, Vol. 101, no 9, p. 1173-1177Article in journal (Refereed)
    Abstract [en]

    New Findings: What is the topic of this review? This review addresses whether a mismatch between cerebral O2 demand and delivery accelerates the development of central fatigue during endurance-type exercise. What advances does it highlight? The difficulty with studying the importance of cerebral O2 availability for exercise performance is to manipulate cerebral O2 availability independently of muscular O2 availability. The different approaches to overcome this limitation indicate that cerebral oxygenation is not a major limiting factor in normoxia, but may limit performance in submaximal exercise tasks in hypoxia. Central fatigue originates within the central nervous system and is characterized by a decrease in voluntary muscle activation. Reduced systemic O2 availability can facilitate central fatigue by enhancing the afferent input of the chemosensitive nerves that play a pivotal role in development of central fatigue. There is accumulating evidence that, in some situations, inadequate O2 availability to the brain itself promotes central fatigue. This short review presents some of the recent findings supporting a direct effect of inadequate cerebral O2 availability on central fatigue and addresses the persisting limitations.

  • 137.
    Siebenmann, Christoph
    et al.
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Rasmussen, P.
    Sorensen, H.
    Bonne, T. C.
    Zaar, M.
    Aachmann-Andersen, N. J.
    Nordsborg, N. B.
    Secher, N. H.
    Lundby, C.
    Hypoxia increases exercise heart rate despite combined inhibition of beta-adrenergic and muscarinic receptors2015In: American Journal of Physiology. Heart and Circulatory Physiology, ISSN 0363-6135, E-ISSN 1522-1539, Vol. 308, no 12, p. H1540-H1546Article in journal (Refereed)
    Abstract [en]

    Hypoxia increases the heart rate response to exercise, but the mechanism(s) remains unclear. We tested the hypothesis that the tachycardic effect of hypoxia persists during separate, but not combined, inhibition of beta-adrenergic and muscarinic receptors. Nine subjects performed incremental exercise to exhaustion in normoxia and hypoxia (fraction of inspired O-2 = 12%) after intravenous administration of 1) no drugs (Cont), 2) propranolol (Prop), 3) glycopyrrolate (Glyc), or 4) Prop + Glyc. HR increased with exercise in all drug conditions (P < 0.001) but was always higher at a given workload in hypoxia than normoxia (P < 0.001). Averaged over all workloads, the difference between hypoxia and normoxia was 19.8 +/- 13.8 beats/min during Cont and similar (17.2 +/- 7.7 beats/min, P = 0.95) during Prop but smaller (P < 0.001) during Glyc and Prop + Glyc (9.8 +/- 9.6 and 8.1 +/- 7.6 beats/min, respectively). Cardiac output was enhanced by hypoxia (P < 0.002) to an extent that was similar between Cont, Glyc, and Prop + Glyc (2.3 +/- 1.9, 1.7 +/- 1.8, and 2.3 +/- 1.2 l/min, respectively, P > 0.4) but larger during Prop (3.4 +/- 1.6 l/min, P = 0.004). Our results demonstrate that the tachycardic effect of hypoxia during exercise partially relies on vagal withdrawal. Conversely, sympathoexcitation either does not contribute or increases heart rate through mechanisms other than beta-adrenergic transmission. A potential candidate is beta-adrenergic transmission, which could also explain why a tachycardic effect of hypoxia persists during combined beta-adrenergic and muscarinic receptor inhibition.

  • 138.
    Siebenmann, Christoph
    et al.
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Rasmussen, Peter
    Hug, Mike
    Keiser, Stefanie
    Fluck, Daniela
    Fisher, James P.
    Hilty, Matthias P.
    Maggiorini, Marco
    Lundby, Carsten
    Parasympathetic withdrawal increases heart rate after 2 weeks at 3454 m altitude2017In: Journal of Physiology, ISSN 0022-3751, E-ISSN 1469-7793, Vol. 595, no 5, p. 1619-1626Article in journal (Refereed)
    Abstract [en]

    Chronic hypoxia increases resting heart rate (HR), but the underlying mechanism remains incompletely understood. We investigated the relative contributions of the sympathetic and parasympathetic nervous systems, along with potential non-autonomic mechanisms, by individual and combined pharmacological inhibition of muscarinic and/or beta-adrenergic receptors. In seven healthy lowlanders, resting HR was determined at sea level (SL) and after 15-18 days of exposure to 3454 m high altitude (HA) without drug intervention (control, CONT) as well as after intravenous administration of either propranolol (PROP), or glycopyrrolate (GLYC), or PROP and GLYC in combination (PROP+GLYC). Circulating noradrenaline concentration increased from 0.9 +/- 0.4 nmol l(-1) at SL to 2.7 +/- 1.5 nmol l(-1) at HA (P = 0.03). The effect of HA on HR depended on the type of autonomic inhibition (P = 0.006). Specifically, HR was increased at HA from 64 +/- 10 to 74 +/- 12 beats min-(1) during the CONT treatment (P = 0.007) and from 52 +/- 4 to 59 +/- 5 beats min(-1) during the PROP treatment (P < 0.001). In contrast, HR was similar between SL and HA during the GLYC treatment (110 +/- 7 and 112 +/- 5 beats min(-1), P = 0.28) and PROP+ GLYC treatment (83 +/- 5 and 85 +/- 5 beats min(-1), P = 0.25). Our results identify a reduction in cardiac parasympathetic activity as the primary mechanism underlying the elevated HR associated with 2 weeks of exposure to hypoxia. Unexpectedly, the sympathoactivation atHA that was evidenced by increased circulating noradrenaline concentration had little effect on HR, potentially reflecting down-regulation of cardiac beta-adrenergic receptor function in chronic hypoxia. These effects of chronic hypoxia on autonomic control of the heart may concern not only HA dwellers, but also patients with disorders that are associated with hypoxaemia.

  • 139. Simpson, Elizabeth J.
    et al.
    Debevec, Tadej
    Eiken, Ola
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Mekjavic, Igor
    Macdonald, Ian A.
    PlanHab: the combined and separate effects of 16 days of bed rest and normobaric hypoxic confinement on circulating lipids and indices of insulin sensitivity in healthy men2016In: Journal of applied physiology, ISSN 8750-7587, E-ISSN 1522-1601, Vol. 120, no 8, p. 947-955Article in journal (Refereed)
    Abstract [en]

    PlanHab is a planetary habitat simulation study. The atmosphere within future space habitats is anticipated to have reduced PO2, but information is scarce as to how physiological systems may respond to combined exposure to moderate hypoxia and reduced gravity. This study investigated, using a randomized-crossover design, how insulin sensitivity, glucose tolerance, and circulating lipids were affected by 16 days of horizontal bed rest in normobaric normoxia [NBR: FIO2 = 0.209; PIO2 = 133.1 (0.3) mmHg], horizontal bed rest in normobaric hypoxia [HBR: FIO2 = 0.141 (0.004); PIO2 = 90.0 (0.4) mmHg], and confinement in normobaric hypoxia combined with daily moderate intensity exercise (HAMB). A mixed-meal tolerance test, with arterialized-venous blood sampling, was performed in 11 healthy, nonobese men (25-45 yr) before (V1) and on the morning of day 17 of each intervention (V2). Postprandial glucose and c-peptide response were increased at V2 of both bed rest interventions (P < 0.05 in each case), with c-peptide: insulin ratio higher at V2 in HAMB and HBR, both in the fed and fasted state (P < 0.005 in each case). Fasting total cholesterol was reduced at V2 in HAMB [-0.47 (0.36) mmol/l; P < 0.005] and HBR [-0.55 (0.41) mmol/l; P < 0.005]. Fasting HDL was lower at V2 in all interventions, with the reduction observed in HBR [-0.30 (0.21) mmol/l] greater than that measured in HAMB [-0.13 (0.14) mmol/l; P < 0.005] and NBR [-0.17 (0.15) mmol/l; P < 0.05]. Hypoxia did not alter the adverse effects of bed rest on insulin sensitivity and glucose tolerance but appeared to increase insulin clearance. The negative effect of bed rest on HDL was compounded in hypoxia, which may have implications for long-term health of those living in future space habitats.

  • 140. Stavrou, N. A.
    et al.
    McDonnell, A. C.
    Eiken, Ola
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Mekjavic, I. B.
    Indices of psychological strain during hypoxic bedrest and confinement2013In: Proceedings of Life in space for life on earth, 18-22 June 2012, Aberdeen, European Space Agency , 2013Conference paper (Refereed)
    Abstract [en]

    Much attention has been devoted to the physiological changes that occur during bed rest. However, there has been a lack of focus on the psychological aspects per se. We investigated indices of psychological strain during three 10-d interventions, designed to assess the combined effects of inactivity/unloading and normobaric hypoxia on several physiological systems. Eleven male participants underwent three 10-d campaigns in a randomized manner: 1) normobaric hypoxic ambulatory confinement (HAMB), 2) normobaric hypoxic bed rest (HBR) and 3) normoxic bed rest (NBR). The most negative psychological profile appeared on BR10 of HBR and HAmb conditions (hypoxic conditions). Concomitantly a decrease in positive emotions was observed from BR-2 to BR10. Bed rest and exposure to hypoxic environments seems to exert a negative effect on person's psychological mood.

  • 141. Stavrou, N.
    et al.
    McDonnell, A.C.
    Debevec, T.
    Eiken, Ola
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Mekjavic, I.B.
    The effect of moderate exercise on emotional state during hypoxic confinement2014Conference paper (Refereed)
    Abstract [en]

    Normobaric hypoxic training is routinely used by athletes to improve their altitude and sea level performance. A multitude of schedules are being used, combining inactive and active exposure to hypoxic environments. The live high – train low regimen, in particular, requires athletes to spend a majority of time confined to a normobaric hypoxic environment. Despite the known positive effects of hypoxic training on physical performance, there is a lack of information regarding the influence of hypoxia and physical activity on emotional state. This was the principal aim of the current study. Specifically, we tested the hypothesis that physical activity alleviates the hypoxia-induced increases in negative feelings. Fourteen male subjects were confined to 10-day continuous hypoxia (fraction of inspired O2=0.139±0.003; 4000m simulated altitude). Subjects were assigned to either the Hypoxic Confinement: Exercise group (HCE: N=8, two 1 hour training sessions/day at 50% hypoxic peak power output) or the Hypoxic Confinement: Sedentary group (HCS: N=6, no exercise). Subjects were administered the Profile of Mood States (POMS) and the Positive and Negative Affect Schedule (PANAS) tests two days prior to hypoxic confinement (D-2), on days 3 (D3), 7 (D7) and 10 (D10) of hypoxic confinement and on the first day of recovery following the confinement period (R+1). The ANOVA repeated measure of the PANAS determined that positive affect differed significantly across the five time measures between HCS and HCE. Bonferroni post hoc analysis revealed that the HCS group elicited a reduction of positive emotion from D-2 to D7 and to D10 with a concomitant increase of negative emotion from D-2 to D10. In addition, an increase of tension from D-2 to D7 and to D10 was revealed in HCS, whereas an increase in tension on D10 was indicated in HCE. Based on the POMS, an increase of depression from D-2 to D7 was found in HCS, whereas no differences were revealed in HCE, among the five time measures. Finally, no significant differences revealed between D10 and R+1 in the PANAS or POMS in either HCS or HCE. The results indicate that in sedentary subjects hypoxic confinement increases tension and negative emotions, and decreases vigor and positive emotions. It is concluded that hypoxia negatively affects the emotional state, but that increasing the level of physical activity ameliorates such feelings.

  • 142. Stavrou, NAM
    et al.
    Debevec, T
    Eiken, Ola
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology. KTH, School of Technology and Health (STH), Centres, Swedish Aerospace Physiology Centre, SAPC.
    Mekjavic, IB
    PlanHab: Examining the effect of 21-day hypoxic bed rest and confinement on emotional state2015Conference paper (Refereed)
  • 143. Stavrou, N.A.M.
    et al.
    McDonell, A.C.
    Eiken, Ola
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology. KTH, School of Technology and Health (STH), Centres, Swedish Aerospace Physiology Centre, SAPC.
    Mekjavic, I.B.
    Psychological strain: Examining the effect of hypoxic bedrest and confinement2015In: Physiology and Behavior, ISSN 0031-9384, E-ISSN 1873-507X, Vol. 139, p. 497-504Article in journal (Refereed)
    Abstract [en]

    The aim was to assess the effect of a 10-day exposure to the environmental stressors anticipated in future lunar habitats on indices of psychological strain. In addition to the reduced gravity of the Moon, future habitats on the Moon will likely maintain a hypobaric hypoxic environment. The hypobaric environment will eliminate the need for long decompression profiles prior to each extra-vehicular activity. We investigated the indices of psychological strain during three 10-day conditions, designed to assess the separate and combined effects of inactivity/unloading and normobaric hypoxia on several physiological systems. Eleven male participants underwent three 10-day campaigns in a randomised manner: 1) normobaric normoxic bed rest (NBR), 2) normobaric hypoxic bed rest (HBR) and 3) normobaric hypoxic ambulatory confinement (HAMB). The most negative psychological profile appeared on day 10 of the HBR and HAMB (hypoxic) conditions. Concomitantly, a decrease in positive emotions was observed from baseline to day 10 of the HBR and NBR conditions. Thus, confinement in a hypoxic environment seems to exert a negative effect on an individual's psychological mood.

  • 144. Stavrou, Nektarios
    et al.
    Keramidas, Michail E.
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Kounalakis, Stylianos
    Eiken, Ola
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Mekjavic, Igor
    Maximal exercise in hypoxia leads to a profounder negative emotional state2014Conference paper (Refereed)
  • 145.
    Sundblad, Patrik
    et al.
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology. KTH, School of Technology and Health (STH), Centres, Swedish Aerospace Physiology Centre, SAPC.
    Franberg, Oskar
    Siebenmann, Christoph
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology. KTH, School of Technology and Health (STH), Centres, Swedish Aerospace Physiology Centre, SAPC.
    Gennser, Mikael
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology. KTH, School of Technology and Health (STH), Centres, Swedish Aerospace Physiology Centre, SAPC.
    Measuring Uptake and Elimination of Nitrogen in Humans at Different Ambient Pressures2016In: Aerospace Medicine and Human Performance, ISSN 2375-6314, Vol. 87, no 12, p. 1045-1050Article in journal (Refereed)
    Abstract [en]

    BACKGROUND: To measure nitrogen (N-2) wash-out and uptake requires elaborate set-ups, especially when doing the measurements at increased or decreased ambient pressure. Here we present a transportable device for quantifying N-2 turnover in humans which can be used at different ambient pressures. METHODS: A modified close-circuit electronic rebreather was used to assess N-2 turnover. Changes in N-2 volume within the rebreathing circuit, reflecting N-2 uptake or washout, were derived from the continuously monitored total system volume and the calculated volumes of oxygen and water vapor. The calculation of continuous N-2 volume curves was performed off-line using dedicated computer software. RESULTS: Four subjects participated in the proof-of-concept tests. At steady state, the drift in calculated N-2 volume in the rebreathing circuit over a 1-h duration was minimal. Three of the subjects participated in additional N-2 steady-state measurements where 1019 mL (BTPD) of N-2 was injected into the rebreathing circuit over 20 min and the measured volume increase was 1006 +/- 32 mL. Lastly, N-2 elimination was assessed during decompression to 0.5 atm and while breathing hyperoxic gas. N-2 uptake was measured during compression to 1.8 atm. The elimination and uptake curves were deemed to be realistic. DISCUSSION: A method for assessing N-2 turnover in humans has been developed and a first evaluation has been performed. It is easy to work with operationally and can be used at different ambient pressures. More research is needed in order to further validate it as a method for assessing N-2 turnover in humans.

  • 146.
    Sundblad, Patrik
    et al.
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology. KTH, School of Technology and Health (STH), Centres, Swedish Aerospace Physiology Centre, SAPC.
    Kölegård, Roger
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology. KTH, School of Technology and Health (STH), Centres, Swedish Aerospace Physiology Centre, SAPC.
    Eiken, Ola
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology. KTH, School of Technology and Health (STH), Centres, Swedish Aerospace Physiology Centre, SAPC.
    G tolerance and the vasoconstrictor reserve2014In: European Journal of Applied Physiology, ISSN 1439-6319, E-ISSN 1439-6327, Vol. 114, no 12, p. 2521-2528Article in journal (Refereed)
    Abstract [en]

    Because leg arterial stiffness is higher in subjects with high G tolerance, we hypothesized that subjects with high G tolerance would have larger capacity for vasoconstriction. Sixteen subjects, eight with high and eight with low G tolerance (H and L group, respectively), were exposed to a cold pressor test (CPT) in supine and upright posture. Heart rate (HR), mean arterial pressure (MAP) and cardiac output (CO) were measured, and total peripheral resistance (TPR) and stroke volume (SV) were calculated. In the supine position, CPT increased TPR more in the H group; 31 +/- A 18 % than in the L group; 11 +/- A 7 % (p < 0.05). The L group had larger increases in CO than the H group; 17 +/- A 16 vs. 3.4 +/- A 7 % (p = 0.06). In the upright position, the H group had a larger MAP response to CPT than the L group; 26 +/- A 14 vs. 14 +/- A 7 % (p = 0.06). The H group, but not the L group, had significant increases in TPR whereas the L group had significant increases in CO and SV. In response to CPT, the high G tolerance group elevated MAP by increasing TPR, whereas the low G tolerance group showed a dependency on increased CO. The H group seemed to have a larger vasoconstrictor reserve. The results further suggest that vasoconstrictor reserve capacity could constitute the link between the recent finding that indicates a relationship between G tolerance and arterial distensibility in the legs.

  • 147.
    Sundblad, Patrik
    et al.
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology. KTH, School of Technology and Health (STH), Centres, Swedish Aerospace Physiology Centre, SAPC.
    Kölegård, Roger
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology. KTH, School of Technology and Health (STH), Centres, Swedish Aerospace Physiology Centre, SAPC.
    Eiken, Ola
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology. KTH, School of Technology and Health (STH), Centres, Swedish Aerospace Physiology Centre, SAPC.
    Passiv G-tolerans; kardiovaskulära omställningar under G-belastning vis-a-vis under cold-pressor test samt stimulering av arteriella baroreceptorer2014Conference paper (Refereed)
  • 148.
    Sundblad, Patrik
    et al.
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Kölegård, Roger
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Migeotte, P. -F
    Delière, Q.
    Eiken, Ola
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    The arterial baroreflex and inherent G tolerance2016In: European Journal of Applied Physiology, ISSN 1439-6319, E-ISSN 1439-6327, p. 1-9Article in journal (Refereed)
    Abstract [en]

    Purpose: High G tolerance is based on the capacity to maintain a sufficient level of arterial pressure (AP) during G load; therefore, we hypothesized that subjects with high G tolerance (H group) would have stronger arterial baroreflex responses compared to subjects with low G tolerance (L group). The carotid baroreflex was evaluated using the neck pressure method (NP), which assesses open-loop responses. Methods: The carotid baroreflex was tested in 16 subjects, n = 8 in the H and L group, respectively, in the supine and upright posture. Heart rate and AP were measured. Results: There were no differences between groups in the maximum slopes of the carotid baroreflex curves. However, the H group had a larger systolic and mean AP (SAP, MAP) increase to the initial hypotensive stimuli of the NP sequence in the upright position compared to the L group, 7.5 ± 6.6 vs 2.0 ± 2.4 and 4.1 ± 3.4 vs 1.1 ± 1.1 mmHg for SAP and MAP, respectively. Furthermore, the L group exhibited an increased latency between stimuli and response in AP in the upright compared to supine position, 4.1 ± 1.0 vs 3.1 ± 0.9 and 4.7 ± 1.1 vs 3.6 ± 0.9 s, for SAP and MAP. No differences in chronotropic responses were observed between the groups. Conclusions: It is concluded that the capacity for reflexive vasoconstriction and maintained speed of the vascular baroreflex during orthostatic stress are coupled to a higher relaxed GOR tolerance.

  • 149.
    Sundblad, Patrik
    et al.
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology. Swedish Aerospace Physiology Center.
    Orlov, O
    Guidelines for Standardization of Bed Rest Studies in the Spaceflight Context.2015Report (Other academic)
  • 150.
    Sundblad, Patrik
    et al.
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Orlov, O
    Angerer, O
    Larina, IM
    Cromwell, R
    Standardization of Bed Rest Studies in the Spaceflight Context.2016In: Journal of applied physiology, ISSN 8750-7587, E-ISSN 1522-1601, Vol. 121, no 1, p. 348-349Article in journal (Refereed)
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