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  • 1. Alkner, B.
    et al.
    Norrbrand, Lena
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Tesch, P.
    Neuromuscular adaptations following 90 days bed rest with or without resistance exercise.2016In: Aerospace Medicine and Human Performance, ISSN 2375-6322, Vol. 87, no 7, 610-617 p.Article in journal (Refereed)
  • 2. Amon, M
    et al.
    Keramidas, Michail E.
    Kounalakis, S
    Kölegård, Roger
    KTH, School of Technology and Health (STH), Environmental Physiology (Closed 20130701).
    Simpson, L
    MacDonald, I
    Eiken, Ola
    KTH, School of Technology and Health (STH), Environmental Physiology (Closed 20130701).
    Mekjavic, IB
    Effect of hypoxia on postprandial blood glucose and insulin response2011Conference paper (Refereed)
  • 3. Arvedsen, SK
    et al.
    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.
    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.
    Petersen, L. G.
    Damgaard, M.
    Body height and arterial pressure in seated and supine young males during +2 G centrifugation2015In: American Journal of Physiology. Regulatory Integrative and Comparative Physiology, ISSN 0363-6119, E-ISSN 1522-1490, Vol. 309, no 9Article in journal (Refereed)
    Abstract [en]

    It is known that arterial pressure correlates positively with body height in males and it has been suggested that this is due to the increasing vertical hydrostatic gradient from the heart to the carotid baroreceptors. Therefore we tested the hypothesis that a higher gravitoinertial stress induced by the use of a human centrifuge would increase mean arterial pressure (MAP) more in tall than in short males in the seated position. In short (162-171cm, n=8) and tall (194-203cm, n=10) healthy males (18-41y), brachial arterial pressure, heart rate (HR) and cardiac output were measured during +2G centrifugation, while they were seated upright with the legs kept horizontal (+2Gz). In a separate experiment, the same measurements were done with the subjects supine (+2Gx). During +2Gz MAP increased in the short (22±2 mmHg, p<0.0001) and tall (23±2 mmHg, p<0.0001) males, with no significant difference between the groups. HR increased more (p<0.05) in the tall than in the short group (14±2 versus 7±2 bpm). Stroke volume (SV) decreased in the short group (26±4 mL, p=0.001) and more so in the tall group (39±5 mL, p<0.0001; short vs tall p=0.047). During +2GX, systolic arterial pressure increased (p<0.001) and SV (p=0.012) decreased in the tall group only. In conclusion, during +2Gz MAP increased in both short and tall males with no difference between the groups. However, in the tall group HR increased more during +2Gz which could be caused by a larger hydrostatic pressure gradient from heart to head leading to greater inhibition of the carotid baroreceptors.

  • 4. Bali, TC
    et al.
    Kounalakis, SN
    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: The effects of 21-day hypoxic confinement and unloading/inactivity on regional body composition and muscle strength2015Conference paper (Refereed)
  • 5. Bense, L
    et al.
    Eklund, G
    Jorulf, H
    Farkas, A
    Balashazy, I
    Hedenstierna, G
    Krebsz, A
    Balazs, G
    Eden Strindberg, J
    Gennser, Mikael
    KTH, School of Technology and Health (STH), Environmental Physiology.
    Douglas, J
    Perforation of the right main bronchus, detected by HRCT 3D technique2011Conference paper (Refereed)
  • 6. Bense, L
    et al.
    Jorulf, H
    Farkas, A
    Eden-Strindberg, J
    Gennser, Mikael
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Jokay, A
    Krebsz, A
    Pulmonary gas conducting interstitial pathway2015In: Acta Radiologica Open, ISSN 2058-4601, Vol. 4, no 10, 1-5 p.Article in journal (Refereed)
    Abstract [en]

    In spite of the growing efforts oriented towards revealing different aspects of emphysema, the persistence of the emphysematous or emphysema-like changes (ELCs) is not explored yet in the open literature. In this study we demonstrate the persistence of an ELC for 22 years in a spontaneous pneumothorax (SP) patient which indicates a hitherto unknown gas supply to the ELC. For this purpose we used high resolution computed tomography (HRCT) images processed into three-dimensional (3D) geometry. By the same token, not only a long persistence but also the volume increase of this ELC between 2002 and 2010 was demonstrated. The 3D geometry visualized an aerated interstitial structure between the sites of supposed gas leakage at the wall of the third generation airways and the ELC. This potential gas conducting interstitial pathway is not a continuation and has neither the form nor the structure of a bronchus. The finding suggests that in this patient the intrabronchial gas passes through the bronchial wall and via a gas conducting interstitial pathway reaches the ELC. Despite the availability of the presently employed techniques for at least 15 years, such case and phenomenon have not been described previously. The retrieval of the patient suggests that the findings could be relevant for a considerable proportion of the population.

  • 7. Blogg, L
    et al.
    Gennser, Mikael
    KTH, School of Technology and Health (STH), Environmental Physiology.
    Direct comparison of audio Doppler ultrasound scores and 2D ultrasound images of venous gas emboli.2010Conference paper (Refereed)
  • 8. Blogg, L
    et al.
    Gennser, Mikael
    KTH, School of Technology and Health (STH), Environmental Physiology.
    Near maximal venous bubble scores and arterial bubbles with no signs or symptoms of DCS - a case study.2011Conference paper (Refereed)
  • 9. Blogg, L
    et al.
    Gennser, Mikael
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Jurd, KM
    Møllerløkken, A
    Observed incidence of decompression sickness and venous gas bubbles following 18 M dives on RN table 11/Norwegian air diving table2015Conference paper (Refereed)
  • 10. Blogg, S. Lesley
    et al.
    Gennser, Mikael
    KTH, School of Technology and Health (STH), Environmental Physiology.
    The need for optimisation of post-dive ultrasound monitoring to properly evaluate the evolution of venous gas emboli2011In: Diving and hyperbaric medicine : the journal of the South Pacific Underwater Medicine Society, ISSN 1833-3516, Vol. 41, no 3, 139-146 p.Article in journal (Refereed)
    Abstract [en]

    Audio Doppler ultrasound and echocardiographic techniques are useful tools for investigating the formation of inert gas bubbles after hyperbaric exposure and can help to assess the risk of occurrence of decompression sickness. However, techniques, measurement period and regularity of measurements must be standardised for results to be comparable across research groups and to be of any benefit. There now appears to be a trend for fewer measurements to be made than recommended, which means that the onset, peak and cessation of bubbling may be overlooked and misreported. This review summarises comprehensive Doppler data collected over 15 years across many dive profiles and then assesses the effectiveness of measurements made between 30 and 60 minutes (min) post-dive (commonly measured time points made in recent studies) in characterising the evolution and peak of venous gas emboli (VGE). VGE evolution in this dive series varied enormously both intra- and inter-individually and across dive profiles. Median, rather than mean values are best reported when describing data which have a non-linear relation to the underlying number of bubbles, as are median peak grades, rather than maximum, which may reflect only one individual's data. With regard to monitoring, it is apparent that the evolution of VGE cannot be described across multiple dive profiles using measurements made at only 30 to 60 min, or even 90 min post-dive. Earlier and more prolonged measurement is recommended, while the frequency of measurements should also be increased; in doing so, the accuracy and value of studies dependent on bubble evolution will be improved.

  • 11. Blogg, SL
    et al.
    Gennser, Mikael
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    The use of ultrasound bubble detection to develop the Swedish Navy trimix dive tables2015Conference paper (Refereed)
  • 12.
    Buendia, Rubén
    et al.
    KTH, School of Technology and Health (STH), Medical Engineering, Medical sensors, signals and systems.
    Seoane, Fernando
    KTH, School of Technology and Health (STH), Medical Engineering, Medical sensors, signals and systems.
    Bosaeus, I.
    Gil-Pita, R.
    Johannsson, G.
    Ellegård, L.
    Lindecrantz, Kaj
    KTH, School of Technology and Health (STH), Medical Engineering, Medical sensors, signals and systems.
    Robustness study of the different immittance spectra and frequency ranges in bioimpedance spectroscopy analysis for assessment of total body composition2014In: Physiological Measurement, ISSN 0967-3334, E-ISSN 1361-6579, Vol. 35, no 7, 1373-1395 p.Article in journal (Refereed)
    Abstract [en]

    The estimation of body fluids is a useful and common practice for assessment of disease status and therapy outcomes. Electrical bioimpedance spectroscopy (EBIS) methods are noninvasive, inexpensive and efficient alternatives for determination of body fluids. One of the main source of errors in EBIS measurements in the estimation of body fluids is capacitive coupling. In this paper an analysis of capacitive coupling in EBIS measurements was performed and the robustness of the different immittance spectra against it tested. On simulations the conductance (G) spectrum presented the smallest overall error, among all immittance spectra, in the estimation of the impedance parameters used to estimate body fluids. Afterwards the frequency range of 10-500 kHz showed to be the most robust band of the G spectrum. The accuracy of body fluid estimations from the resulting parameters that utilized G spectrum and parameters provided by the measuring device were tested on EBIS clinical measurements from growth hormone replacement therapy patients against estimations performed with dilution methods. Regarding extracellular fluid, the correlation between each EBIS method and dilution was 0.93 with limits of agreement of 1.06 +/- 2.95 l for the device, 1.10 +/- 2.94 l for G [10-500 kHz] and 1.04 +/- 2.94 l for G [5-1000 kHz]. Regarding intracellular fluid, the correlation between dilution and the device was 0.91, same as for G [10-500 kHz] and 0.92 for G [5- 1000 kHz]. Limits of agreement were 0.12 +/- 4.46 l for the device, 0.09 +/- 4.45 for G [10- 500 kHz] and 0.04 +/- 4.58 for G [5-1000 kHz]. Such close results between the EBIS methods validate the proposed approach of using G spectrum for initial Cole characterization and posterior clinical estimation of body fluids status.

  • 13. Ciuha, U
    et al.
    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: Effects of normobaric hypoxic bed rest on behavioural temperature regulation2015Conference paper (Refereed)
  • 14. Ciuha, U
    et al.
    Grönkvist, Mikael
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Mekjavic, B.
    Eiken, Ola
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Strategies for increasing evaporative cooling during simulated desert patrol mission.2016In: Ergonomics, ISSN 0014-0139, E-ISSN 1366-5847, Vol. 59, no 2Article in journal (Refereed)
    Abstract [en]

    The study evaluated the efficiency of two heat dissipation strategies under simulated desert patrol missions. Ten men participated in four trials, during which they walked on a treadmill (45°C, 20% relative humidity), carrying a load of 35 kg; two 50-min walks were separated by a 20-min rest. Cooling strategies, provided by an ambient air-ventilated vest (active cooling condition, AC), or water spraying of the skin during the rest (passive cooling condition, PC), in addition to reduced clothing and open zippers, were compared to conditions with full protective (FP) clothing and naked condition (NC). Skin temperature was higher during NC (37.9 ± 0.4°C; p < 0.001), and rectal temperature and heart rate were higher during FP (38.6 ± 0.4°C, p < 0.001 and 145 ± 12, p < 0.001, respectively), compared to other conditions. Four subjects terminated the trial prematurely due to signs of heat exhaustion in FP. Both cooling strategies substantially improved evaporative cooling.

  • 15. Ciuha, U
    et al.
    Grönkvist, Mikael
    KTH, School of Technology and Health (STH), Environmental Physiology.
    Mekjavic, I
    Kölegård, Roger
    KTH, School of Technology and Health (STH), Environmental Physiology.
    Pavlinič, D
    Eiken, Ola
    KTH, School of Technology and Health (STH), Environmental Physiology.
    Thermal strain in soldiers performing patrol missions in a desert climate: effect of two different cooling strategies2011Conference paper (Refereed)
  • 16. De Boever, P
    et al.
    Louwies, T
    Kounalakis, Stylianos
    Jaki Mekjavic, P
    Eiken, Ola
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Mekjavic, I.B.
    In vivo retinal images for a non-invasive analysis of the microcirculation during hypoxia and unloading/inactivity2013Conference paper (Refereed)
  • 17. Debevec, T
    et al.
    Amon, M
    Keramidas, Michail E.
    KTH, School of Technology and Health (STH), Environmental Physiology (Closed 20130701).
    Kounalakis, S.N.
    Mekjavic, I.B.
    Hematological responses to two different intermittent hypoxic training regimens2009Conference paper (Refereed)
    Abstract [en]

    "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.

  • 18. Debevec, T
    et al.
    Amon, Mojca
    Keramidas, Michail E.
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Kounalakis, S.N.
    Pisot, R
    Mekjavic, I.B.
    Normoxic and hypoxic performance following four weeks of normobaric hypoxic training2010In: Aviation, Space and Environmental Medicine, ISSN 0095-6562, E-ISSN 1943-4448, Vol. 81, no 4, 387-393 p.Article in journal (Refereed)
    Abstract [en]

    INTRODUCTION:

    Although training in hypoxia has been suggested to improve sea level and altitude performance, most studies have only evaluated its effect on maximal aerobic capacity in either normoxia or hypoxia. The present study evaluated the effect of a live low-train high training regimen on both normoxic and hypoxic endurance performance and aerobic capacity.

    METHODS:

    There were 18 male subjects who performed 20 training sessions in either a normoxic (F(IO2) = 0.21) or hypoxic (F(IO2) = 0.12) environment. Both the Control (N = 9) and Hypoxic (N = 9) group subjects trained at an intensity that maintained their heart rate at a level corresponding to that elicited at 50% of peak power output attained in normoxia or hypoxia, respectively. Before, during, upon completion, and 10 d after the protocol, subjects' aerobic capacity (VO2 peak) and endurance performance (80% of VO2 peak) were determined under normoxic and hypoxic conditions.

    RESULTS:

    Mean +/- SD normoxic VO2 peak increased significantly only in the Control group from 45.7 +/- 6.1 to 53.9 +/- 3.9 (ml x kg(-1) x min(-1)), whereas hypoxic VO2 peak did not improve in either group. The Control group exhibited significant improvements in normoxic, but not hypoxic peak power output (PPO) and time to exhaustion, whereas the Hypoxic group only exhibited improvements in normoxic time to exhaustion. During each testing period, we also assessed pulmonary function, selected hematological variables, and anthropometry. There were no significant changes in these variables in either group after the training protocol.

    CONCLUSION:

    The hypoxic training regimen used in the present study had no significant effect on altitude and sea level performance.

  • 19. Debevec, T
    et al.
    Ehrström, S
    Pialoux, V
    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
    Millet, GP
    FemHab: Prooxidant/antioxidant balance during and following a 10-day hypoxic bed rest2015Conference paper (Refereed)
    Abstract [en]

    Introduction:Inhabitants of the envisaged planetary habitats will be continuously exposed to reduced gravity and hypoxia. The combined effects of unloading and hypoxia on prooxidant/antioxidant balance are currently unknown.

    Methods:Healthy female participants underwent the following three, 10-day interventions: i) Normobaric normoxic bed-rest (NBR; n=11; FiO2=0.209) ii) Normobaric hypoxic ambulatory confinement (HAMB; n=9: FiO2~0.141), and iii) Normobaric hypoxic bed-rest (HBR; n=12; FiO2~0.141). Plasma oxidative stress [advanced oxidation protein products (AOPP) and nitrotyrosine], antioxidant markers [superoxide dismutase (SOD) and glutathione peroxidase (GPX)] and nitrites were determined before (Pre), during (Day 2, Day 6), immediately after (Post) and 24-hrs after (Post+1) each campaign.

    Results:Compared to Pre, the AOPP was only higher on Day 2, Day 6 and Post during the HBR and at Post during the NBR (P<0.05) while the nitrotyrosine was significantly reduced at Post+1 only during the HAMB (P<0.05). Higher levels of SOD were observed during the HAMB at Day 6 and Post+1whereas GPX was reduced at Day 6 and Post during the HBR. Nitrites were significantly higher at Post+1 in the HAMB both, compared to Pre and compared to HBR and NBR (P<0.05).

    Conclusion:These data suggest that the unloading-induced oxidative stress is exacerbated by exposure to simulated altitude of ~4000m. In addition, even habitual (low) physical activity, performed during hypoxic exposure, seems to blunt hypoxia-related oxidative stress via antioxidant system upregulation.

  • 20. Debevec, T
    et al.
    McDonnell, A.C.
    MacDonald, I
    Eiken, Ola
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Mekjavic, I.B.
    Changes in body composition and dietary intake as a consequence of 10-day hypoxic confinement and unloading/inactivityIn: Applied Physiology, Nutrition and Metabolism, ISSN 1715-5312, E-ISSN 1715-5320Article in journal (Refereed)
  • 21. Debevec, T.
    et al.
    Pialoux, V.
    Mekjavic, I.B.
    Eiken, Ola
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Mury, P.
    Millet, G.P.
    Moderate exercise blunts oxidative stress induced by normobaric hypoxic confinement2014In: Medicine & Science in Sports & Exercise, ISSN 0195-9131, E-ISSN 1530-0315, Vol. 46, no 1, 33-41 p.Article in journal (Refereed)
    Abstract [en]

    PURPOSE: Both acute hypoxia and physical exercise are known to increase oxidative stress. This randomized prospective trial investigated whether the addition of moderate exercise can alter oxidative stress induced by continuous hypoxic exposure. METHODS: Fourteen male participants were confined to 10-d continuous normobaric hypoxia (FIO2 = 0.139 ± 0.003, PIO2 = 88.2 ± 0.6 mm Hg, ∼4000-m simulated altitude) either with (HCE, n = 8, two training sessions per day at 50% of hypoxic maximal aerobic power) or without exercise (HCS, n = 6). Plasma levels of oxidative stress markers (advanced oxidation protein products [AOPP], nitrotyrosine, and malondialdehyde), antioxidant markers (ferric-reducing antioxidant power, superoxide dismutase, glutathione peroxidase, and catalase), nitric oxide end-products, and erythropoietin were measured before the exposure (Pre), after the first 24 h of exposure (D1), after the exposure (Post) and after the 24-h reoxygenation (Post + 1). In addition, graded exercise test in hypoxia was performed before and after the protocol. RESULTS: Maximal aerobic power increased after the protocol in HCE only (+6.8%, P < 0.05). Compared with baseline, AOPP was higher at Post + 1 (+28%, P < 0.05) and nitrotyrosine at Post (+81%, P < 0.05) in HCS only. Superoxide dismutase (+30%, P < 0.05) and catalase (+53%, P < 0.05) increased at Post in HCE only. Higher levels of ferric-reducing antioxidant power (+41%, P < 0.05) at Post and lower levels of AOPP (-47%, P < 0.01) at Post + 1 were measured in HCE versus HCS. Glutathione peroxidase (+31%, P < 0.01) increased in both groups at Post + 1. Similar erythropoietin kinetics was noted in both groups with an increase at D1 (+143%, P < 0.01), a return to baseline at Post, and a decrease at Post + 1 (-56%, P < 0.05). CONCLUSIONS: These data provide evidence that 2 h of moderate daily exercise training can attenuate the oxidative stress induced by continuous hypoxic exposure.

  • 22. Debevec, T
    et al.
    Simpson, EJ
    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
    Macdonald, IA
    PlanHab: The individual and combined effects of inactivity and hypoxia on insulin resistance2015Conference paper (Refereed)
    Abstract [en]

    Inactivity is know to aggravate insulin resistance. The effects of hypoxia on insulin and glucose metabolism, on the other hand, are not completely understood.

  • 23. Debevec, Tadej
    et al.
    Bali, Tarsi C.
    Simpson, Elizabeth J.
    Macdonald, Ian 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, Igor B.
    Separate and combined effects of 21-day bed rest and hypoxic confinement on body composition2014In: European Journal of Applied Physiology, ISSN 1439-6319, E-ISSN 1439-6327, Vol. 114, no 11, 2411-2425 p.Article in journal (Refereed)
    Abstract [en]

    This study tested the hypothesis that hypoxia exacerbates reductions in body mass observed during unloading. To discern the separate and combined effects of simulated microgravity and hypoxia, 11 healthy males underwent three 21-day campaigns in a counterbalanced fashion: (1) normoxic bed rest (NBR; FiO2 = 0.209; PiO2 = 133.1 +/- A 0.3); (2) hypoxic ambulatory confinement (HAMB; FiO2 = 0.141 +/- A 0.004; PiO2 = 90.0 +/- A 0.4; similar to 4,000 m); and (3) hypoxic bed rest (HBR; FiO2 = 0.141 +/- A 0.004; PiO2 = 90.0 +/- A 0.4). The same dietary menu was applied in all campaigns. Targeted energy intakes were estimated individually using the Harris-Benedict equation taking into account whether the subjects were bedridden or ambulatory. Body mass and water balance were assessed throughout the campaigns. Whole body and regional body composition was determined before and after the campaigns using dual-energy X-ray absorptiometry. Before and during the campaigns, indirect calorimetry and visual analogue scores were employed to assess the resting energy expenditure (REE) and perceived appetite sensations, respectively. Energy intakes were lower than targeted in all campaigns (NBR: -5 %; HAMB: -14 %; HBR: -6 %; P < 0.01). Body mass significantly decreased following all campaigns (NBR: -3 %; HAMB: -4 %; HBR: -5 %; P < 0.01). While fat mass was not significantly altered, the whole body fat free mass was reduced (NBR: -4 %; HAMB: -5 %; HBR: -5 %; P < 0.01), secondary to lower limb fat-free mass reduction. Water balance was comparable between the campaigns. No changes were observed in REE and perceived appetite. Exposure to simulated altitude of similar to 4,000 m does not seem to worsen the whole body mass and fat-free mass reductions or alter resting energy expenditure and appetite during a 21-day simulated microgravity.

  • 24. Debevec, Tadej
    et al.
    Keramidas, Michail E.
    Norman, Barbara
    Gustafsson, Thomas
    Eiken, Ola
    KTH, School of Technology and Health (STH), Environmental Physiology (Closed 20130701).
    Mekjavic, Igor B.
    Acute short-term hyperoxia followed by mild hypoxia does not increase EPO production: resolving the "normobaric oxygen paradox''2012In: European Journal of Applied Physiology, ISSN 1439-6319, E-ISSN 1439-6327, Vol. 112, no 3, 1059-1065 p.Article in journal (Refereed)
    Abstract [en]

    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.

  • 25. Debevec, Tadej
    et al.
    McDonnell, Adam C.
    Macdonald, Ian A.
    Eiken, Ola
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Mekjavic, Igor B.
    Whole body and regional body composition changes following 10-day hypoxic confinement and unloading-inactivity2014In: Applied Physiology, Nutrition and Metabolism, ISSN 1715-5312, E-ISSN 1715-5320, Vol. 39, no 3, 386-395 p.Article in journal (Refereed)
    Abstract [en]

    Future planetary habitats will expose inhabitants to both reduced gravity and hypoxia. This study investigated the effects of short-term unloading and normobaric hypoxia on whole body and regional body composition (BC). Eleven healthy, recreationally active, male participants with a mean (SD) age of 24 (2) years and body mass index of 22.4 (3.2) kg.m(-2) completed the following 3 10-day campaigns in a randomised, cross-over designed protocol: (i) hypoxic ambulatory confinement (HAMB; FIO2 = 0.147 (0.008); PIO2 = 93.8 (0.9) mm Hg), (ii) hypoxic bed rest (HBR; FIO2 = 0.147 (0.008); PIO2 = 93.8 (0.9) mm Hg), and (iii) normoxic bed rest (NBR; FIO2 = 0.209; PIO2 = 133.5 (0.7) mmHg). Nutritional requirements were individually precalculated and the actual intake was monitored throughout the study protocol. Body mass, whole body, and regional BC were assessed before and after the campaigns using dual-energy X-ray absorptiometry. The calculated daily targeted energy intake values were 2071 (170) kcal for HBR and NBR and 2417 (200) kcal for HAMB. In both HBR and NBR campaigns the actual energy intake was within the targeted level, whereas in the HAMB the intake was lower than targeted (-8%, p < 0.05). Body mass significantly decreased in all 3 campaigns (-2.1%, -2.8%, and -2.0% for HAMB, HBR, and NBR, respectively; p < 0.05), secondary to a significant decrease in lean mass (-3.8%, -3.8%, -4.3% for HAMB, HBR, and NBR, respectively; p < 0.05) along with a slight, albeit not significant, increase in fat mass. The same trend was observed in the regional BC regardless of the region and the campaign. These results demonstrate that, hypoxia per se, does not seem to alter whole body and regional BC during short-term bed rest.

  • 26. Debevec, Tadej
    et al.
    Pialoux, Vincent
    Ehrström, Sabine
    Ribon, Alexandra
    Eiken, Ola
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Mekjavic, Igor B.
    Millet, Gregoire P.
    FemHab: The effects of bed rest and hypoxia on oxidative stress in healthy women2016In: Journal of applied physiology, ISSN 8750-7587, E-ISSN 1522-1601, Vol. 120, no 8, 930-938 p.Article in journal (Refereed)
    Abstract [en]

    Independently, both inactivity and hypoxia augment oxidative stress. This study, part of the FemHab project, investigated the combined effects of bed rest-induced unloading and hypoxic exposure on oxidative stress and antioxidant status. Healthy, eumenorrheic women were randomly assigned to the following three 10-day experimental interventions: normoxic bed rest (NBR; n = 11; PIO2 = 133 mmHg), normobaric hypoxic bed rest (HBR; n = 12; PIO2 = 90 mmHg), and ambulatory hypoxic confinement (HAMB; n = 8: PIO2 = 90 mmHg). Plasma samples, obtained before (Pre), during (D2, D6), immediately after (Post) and 24 h after (Post + 1) each intervention, were analyzed for oxidative stress markers [advanced oxidation protein products (AOPP), malondialdehyde (MDA), and nitrotyrosine], antioxidant status [ superoxide dismutase (SOD), catalase, ferric-reducing antioxidant power (FRAP), glutathione peroxidase (GPX), and uric acid (UA)], NO metabolism end-products (NOx), and nitrites. Compared with baseline, AOPP increased in NBR and HBR on D2 (+ 14%; + 12%; P < 0.05), D6 (+ 19%; + 15%; P < 0.05), and Post (+ 22%; + 21%; P < 0.05), respectively. MDA increased at Post + 1 in NBR (+ 116%; P < 0.01) and D2 in HBR (+114%; P < 0.01) and HAMB (+ 95%; P < 0.05). Nitrotyrosine decreased (-45%; P < 0.05) and nitrites increased (+46%; P < 0.05) at Post + 1 in HAMB only. Whereas SOD was higher at D6 (+ 82%) and Post + 1 (+ 67%) in HAMB only, the catalase activity increased on D6 (128%) and Post (146%) in HBR and HAMB, respectively (P < 0.05). GPX was only reduced on D6 (- 20%; P < 0.01) and Post (- 18%; P < 0.05) in HBR. No differences were observed in FRAP and NOx. UA was higher at Post in HBR compared with HAMB (P < 0.05). These data indicate that exposure to combined inactivity and hypoxia impairs prooxidant/antioxidant balance in healthy women. Moreover, habitual activity levels, as opposed to inactivity, seem to blunt hypoxia-related oxidative stress via antioxidant system upregulation.

  • 27. Dolenc Grošelj, L
    et al.
    Morrisson, SA
    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.
    Mekjavic, IB
    PlanHab: Periodic breathing during hypoxic bedrest2015Conference paper (Refereed)
  • 28.
    Eiken, Ola
    et al.
    KTH, School of Technology and Health (STH), Environmental Physiology.
    Bergsten, Eddie
    KTH, School of Technology and Health (STH), Environmental Physiology.
    Grönkvist, Mikael
    KTH, School of Technology and Health (STH), Environmental Physiology.
    G-protection mechanisms afforded by the anti-G suit abdominal bladder with and without pressure breathing.2011In: Aviation, Space and Environmental Medicine, ISSN 0095-6562, E-ISSN 1943-4448, Vol. 82, no 10, 972-7 p.Article in journal (Refereed)
    Abstract [en]

    BACKGROUND: G protection afforded by the abdominal bladder of a pneumatic anti-G suit is usually attributed to counteraction of G-induced caudad displacement of the heart and pooling of blood in the abdominal veins. The study examined whether the abdominal bladder might provide G protection also via other mechanisms.

    METHODS: Each subject was exposed to +Gz loads while sitting relaxed, wearing a full-coverage anti-G suit modified to permit separate pressurization of the abdominal and leg bladders. In two experimental series (N = 8, N = 14), subjects were breathing at positive airway pressure (PPB); in a third series, five subjects were breathing at atmospheric airway pressure. Intrathoracic pressures were estimated by use of esophageal catheters.

    RESULTS: During PPB at high G loads, intrathoracic pressure was higher with than without the pressurized abdominal bladder. In 7 of the 14 subjects, basilar intrathoracic pressure exceeded airway pressure during PPB when the abdominal bladder was pressurized. The mean arterial pressure response at high G loads was higher in this subset of subjects (55 +/- 23 mmHg) than in the subjects in whom airway pressure exceeded intrathoracic pressure (41 +/- 27 mmHg). Without PPB at increased G load, the intrathoracic pressure gradient was higher with than without the pressurized abdominal bladder.

    DISCUSSION: During PPB, the abdominal bladder acts as an airway counterpressure, thereby facilitating pressure transmission from the airways to the thorax and hence improving G protection. It also appears that in several individuals, pressure may be transmitted from the abdominal bladder to the thorax and heart.

  • 29.
    Eiken, Ola
    et al.
    KTH, School of Technology and Health (STH), Environmental Physiology.
    Danielsson, Ulf
    Hallberg, M
    Mekjavic, IB
    Babic, J
    Kounalakis, S
    Energy expenditure during simulated patrol in darkness2011Conference paper (Refereed)
  • 30.
    Eiken, Ola
    et al.
    KTH, School of Technology and Health (STH), Environmental Physiology (Closed 20130701).
    Grönkvist, Mikael
    KTH, School of Technology and Health (STH), Environmental Physiology (Closed 20130701).
    Signs and symptoms during supra-tolerance +Gz exposures, with reference to G-garment failure.2013In: Aviation, Space and Environmental Medicine, ISSN 0095-6562, E-ISSN 1943-4448, Vol. 84, no 3, 196-205 p.Article in journal (Refereed)
    Abstract [en]

    Introduction: +Gz exposure above the tolerance threshold typically induces a sequence of symptoms/signs, with loss of: peripheral vision, central vision (black out), and consciousness (G-LOC). The aims of this study were to investigate: 1) whether G history influences latent time to, or sequence of, symptoms/signs upon G exposures exceeding the tolerance threshold; and 2) how pilots respond to a sudden loss of pressure in the anti-G garment (AGG) in flight-like scenarios. Methods: There were 14 subjects who were exposed to rapid onset rate +Gz-time profiles, with plateaus 1 and 2 G above the relaxed tolerance level, without initial pressurization of the AGG (NoAGG) and when losing AGG pressure after 10 (AGG_10) and 120 (AGG_120) s at the plateau. Simulated target-chase flights during which AGG pressure was released were performed by seven pilots; the pilot was instructed to behave as during real flight. Results: Latent time to symptoms was shorter at +2 G than at +1 G, and shorter in AGG_10 and AGG_120 than in NoAGG. In AGG_120, 43 and 64% of the subjects experienced serious symptoms (black out, Almost LOC, G-LOC) at +1 and +2 G, respectively, compared to 21 and 54% in AGG_10 and 7 and 29% in NoAGG. The incidence of A-LOC/G-LOC was higher in AGG_10 and especially in AGG_120 than in NoAGG. During the target chase, one pilot did not notice the pressure loss, one experienced G-LOC, and two A-LOC. Discussion: The risk of serious consequences of G exposure exceeding the tolerance level appears to be greater when G-garment failure occurs after a prolonged than after a brief exposure.

  • 31.
    Eiken, Ola
    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.
    Mekjavic, Igor, B
    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.
    PlanHab: Normobaric hypoxia may exaggerate bedrest-induced reductions in peak oxygen uptake2015In: International Society for Gravitational Physiology, 2015Conference paper (Refereed)
  • 32.
    Eiken, Ola
    et al.
    KTH, School of Technology and Health (STH), Environmental Physiology (Closed 20130701).
    Mekjavic, I.
    Sundblad, Patrik
    KTH, School of Technology and Health (STH), Environmental Physiology (Closed 20130701).
    Kölegård, Roger
    KTH, School of Technology and Health (STH), Environmental Physiology (Closed 20130701).
    G tolerance vis-à-vis pressure-distension and pressure-flow relationships of leg arteries2012In: European Journal of Applied Physiology, ISSN 1439-6319, E-ISSN 1439-6327, Vol. 112, no 10, 3619-3627 p.Article in journal (Refereed)
    Abstract [en]

    During increased gravitoinertial (G) load in the head-to-foot direction, pressures in dependent vascular beds are commonly raised to levels capable of distending precapillary vessels, which, in turn, may reduce arterial pressure, and hence compromise the capacity to withstand G load (G tolerance). We hypothesized that distensibility in precapillary leg vessels would be lower in a group of subjects possessing high G tolerance (H; n = 7; relaxed G tolerance = 6.6 ± 0.8 G) than in a group with low G tolerance (L; n = 8; G tolerance = 3.9 ± 0.3 G). The groups were matched with regard to gender, age, weight, height, and resting arterial pressure. Arterial pressure-distension and pressure-flow experiments were performed with the subject supine in a pressure chamber with a lower leg protruding to the outside. Increased intravascular pressure in the blood vessels of the outside leg was accomplished by stepwise increasing chamber pressure to 240 mmHg. Diameter and flow in the posterior tibial artery were measured by ultrasonographic/Doppler techniques. Pressure-induced increments in arterial diameter and flow were more pronounced (p < 0.03) in the L (14.1 ± 4.2% and 32 ± 21 ml/min respectively) than in the H (1.7 ± 5.0% and 1.6 ± 25 ml/min) group, and the pressure thresholds at which these increments commenced were lower (by 52 and 48 mmHg, respectively) in the L than in the H group (p < 0.04). Negative correlations were observed between G tolerance and the increments in diameter and flow (p < 0.02). Thus, the wall stiffness of precapillary leg vessels is greater in individuals with high relaxed G tolerance; whether a causal relationship exists remains to be established.

  • 33.
    Eiken, Ola
    et al.
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Mekjavic, I.B.
    The hypoxic bedrest research programme2013Conference paper (Refereed)
  • 34.
    Eiken, Ola
    et al.
    KTH, School of Technology and Health (STH), Environmental Physiology.
    Mekjavic, IB
    Kounalakis, S
    Kölegård, Roger
    KTH, School of Technology and Health (STH), Environmental Physiology.
    Stiffness in leg arteries/arterioles is reduced by prolonged bedrest.2011Conference paper (Refereed)
  • 35.
    Eiken, Ola
    et al.
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Mekjavic, IB
    Kounalakis, SN
    Kölegård, Roger
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Pressure distension in leg vessels as influenced by prolonged bed rest and a pressure habituation regimen2016In: Journal of applied physiology, ISSN 8750-7587, E-ISSN 1522-1601, Vol. 120, no 12, 1458-1465 p.Article in journal (Refereed)
    Abstract [en]

    Bed rest increases pressure distension in arteries, arterioles, and veins of the leg. We hypothesized that bed-rest-induced deconditioning of leg vessels is governed by the removal of the local increments in transmural pressure induced by assuming erect posture and, therefore, can be counteracted by intermittently increasing local transmural pressure during the bed rest. Ten men underwent 5 wk of horizontal bed rest. A subatmospheric pressure (-90 mmHg) was intermittently applied to one lower leg [pressure habituation (PH) leg]. Vascular pressure distension was investigated before and after the bed rest, both in the PH and control (CN) leg by increasing local distending pressure, stepwise up to +200 mmHg. Vessel diameter and blood flow were measured in the posterior tibial artery and vessel diameter in the posterior tibial vein. In the CN leg, bed rest led to 5-fold and 2.7-fold increments (P < 0.01) in tibial artery pressure-distension and flow responses, respectively, and to a 2-fold increase in tibial vein pressure distension. In the PH leg, arterial pressure-distension and flow responses were unaffected by bed rest, whereas bed rest led to a 1.5-fold increase in venous pressure distension. It thus appears that bed-rest-induced deconditioning of leg arteries, arterioles, and veins is caused by removal of gravity-dependent local pressure loads and may be abolished or alleviated by a local pressure-habituation regimen.

  • 36.
    Eiken, Ola
    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.
    Mekjavic, Igor B.
    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.
    Blood pressure regulation V: in vivo mechanical properties of precapillary vessels as affected by long-term pressure loading and unloading2014In: European Journal of Applied Physiology, ISSN 1439-6319, E-ISSN 1439-6327, Vol. 114, no 3, 499-509 p.Article, review/survey (Refereed)
    Abstract [en]

    Recent studies are reviewed, concerning the in vivo wall stiffness of arteries and arterioles in healthy humans, and how these properties adapt to iterative increments or sustained reductions in local intravascular pressure. A novel technique was used, by which arterial and arteriolar stiffness were determined as changes in arterial diameter and flow, respectively, during graded increments in distending pressure in the blood vessels of an arm or a leg. Pressure-induced increases in diameter and flow were smaller in the lower leg than in the arm, indicating greater stiffness in the arteries/arterioles of the leg. A 5-wk period of intermittent intravascular pressure elevations in one arm reduced pressure distension and pressure-induced flow in the brachial artery by about 50%. Conversely, prolonged reduction of arterial/arteriolar pressure in the lower body by 5 wks of sustained horizontal bedrest, induced three-fold increases of the pressure-distension and pressure-flow responses in a tibial artery. Thus, the wall stiffness of arteries and arterioles are plastic properties that readily adapt to changes in the prevailing local intravascular pressure. The discussion concerns mechanisms underlying changes in local arterial/arteriolar stiffness as well as whether stiffness is altered by changes in myogenic tone and/or wall structure. As regards implications, regulation of local arterial/arteriolar stiffness may facilitate control of arterial pressure in erect posture and conditions of exaggerated intravascular pressure gradients. That increased intravascular pressure leads to increased arteriolar wall stiffness also supports the notion that local pressure loading may constitute a prime mover in the development of vascular changes in hypertension.

  • 37. Ekblom, M. M.
    et al.
    Eriksson, Martin
    KTH, School of Technology and Health (STH), Medical sensors, signals and systems (MSSS).
    Concurrent EMG feedback acutely improves strength and muscle activation2012In: European Journal of Applied Physiology, ISSN 1439-6319, E-ISSN 1439-6327, Vol. 112, no 5, 1899-1905 p.Article in journal (Refereed)
    Abstract [en]

    The purpose of this study was to investigate the acute effects of electromyographic (EMG) feedback on muscle activation and strength during maximal voluntary concentric and eccentric muscle actions. 15 females performed two sets of three lengthening and three shortening maximal voluntary isokinetic knee extensions at 20A degrees A s(-1) over 60A degrees range of motion. After the first set, subjects were randomized to either a control group (n = 8) or a feedback group (n = 7). In the second set, the control group performed tasks identical to those in the first set, whereas the feedback group additionally received concurrent visual feedback of the EMGrms from Vastus Medialis (VM). Knee extensor strength and EMG activation of VM, Vastus lateralis (VL) and hamstrings (HAM) were measured during the MVCs. Analyses were performed separately in a 1 s preactivation phase, a 1 s initial movement phase and a 1 s late movement phase. EMG feedback was associated with significantly higher knee extensor strength in all phases (20.5% p < 0.05, 18.2% p < 0.001 and 19% p < 0.001, respectively) for the eccentric MVCs and in the preactivation phase (16.3%, p < 0.001) and initial movement phases (7.2%, p < 0.05) for concentric MVCs. EMG feedback from VM further improved activation in VM and HAM but not VL. These findings suggested that concurrent visual EMG feedback from VM could acutely enhance muscle strength and activation. Before recommending implementation of EMG feedback in resistance training paradigms, the feedback parameters needs to be optimized and its long-term effects needs to be scrutinized.

  • 38.
    Ekstedt, Mirjam
    et al.
    KTH, School of Technology and Health (STH), Health Systems Engineering, Systems Safety and Management.
    Nyberg, Gisela
    Karolinska Institutet.
    Ingre, Michael
    Stockholm University.
    Ekblom, Örjan
    Karolinska Institutet.
    Marcus, Claude
    Karolinska Institutet.
    Sleep, physical activity and BMI in six to ten-year-old children measured by accelerometry: a cross-sectional study2013In: International Journal of Behavioral Nutrition and Physical Activity, ISSN 1479-5868, E-ISSN 1479-5868, Vol. 10, no 82Article in journal (Refereed)
    Abstract [en]

    Background: The aim of this study is to describe the relationship between objective measures of sleep, physical activity and BMI in Swedish pre-adolescents. The day-to-day association between physical activity and sleep quality as well as week-day and weekend pattern of sleep is also described. Method: We conducted a cross sectional study consisted of a cohort of 1.231 children aged six to ten years within the Stockholm county area. Sleep and physical activity were measured by accelerometry during seven consecutive days. Outcome measures are total sleep time, sleep efficiency, sleep start and sleep end; physical activity intensity divided into: sedentary (<1.5 METS), light (1.5 to 3 METS) and moderate-to-vigorous (> 3 METS); and Body Mass Index standard deviations score, BMIsds. Results: Total sleep time decreased with increasing age, and was shorter in boys than girls on both weekdays and weekends. Late bedtime but consistent wake-up time during weekends made total sleep time shorter on weekends than on weekdays. Day-to-day within-subject analysis revealed that moderate-to-vigorous intense physical activity promoted an increased sleep efficiency the following night (CI < 0.001 to 0.047), while total sleep time was not affected (CI -0.003 to 0.043). Neither sleep duration (CI -0.024 to 0.022) nor sleep efficiency (CI -0.019 to 0.028) affected mean physical activity level the subsequent day. The between-subject analysis indicates that the sleep of children characterized by high moderate-to-vigorous physical activity during the day was frequently interrupted (SE = -. 23, P < .01). A negative association between BMIsds and sleep duration was found (-. 10, p < .01). Conclusions: Short sleep duration was associated with high BMI in six to ten year old children. This study underscores the importance of consistent bedtimes throughout the week for promoting sleep duration in preadolescents. Furthermore, this study suggests that a large proportion of intensive physical activity during the day might promote good sleep quality.

  • 39.
    Frånberg, Oskar
    et al.
    KTH, School of Technology and Health (STH), Environmental Physiology.
    Ericsson, M.
    Larsson, Å.
    Lindholm, P.
    Investigation of a Halcyon RB80 semiclosed rebreather in connection with a diving accident2010Conference paper (Refereed)
  • 40.
    Frånberg, Oskar
    et al.
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Gennser, Mikael
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Dödsfall i samband med dykning med återandningsapparater: ett människa–maskin interaktionsproblem2013In: Hygiea, 2013Conference paper (Refereed)
    Abstract [sv]

    Huvuddelen av de rapporterade och undersökta olyckorna med återandningsapparater utlöstes av felaktigt handhavande, eller bristande människa–maskininteraktion.

  • 41.
    Frånberg, Oskar
    et al.
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Gennser, Mikael
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Measurement and modeling of oxygen content in a demand mass ratio injection rebreather2015In: Undersea & Hyperbaric Medicine, ISSN 1066-2936, Vol. 42, no 6, 573-592 p.Article in journal (Refereed)
    Abstract [en]

    Mechanical semi-closed rebreathers do not need oxygen sensors for their functions, thereby reducing the complexity of the system. However, testing and modeling are necessary in order to determine operational limits as well as the decompression obligation and to avoid hyperoxia and hypoxia. Two models for predicting the oxygen fraction in a demand constant mass ratio injection (DCMRI) rebreather for underwater use were compiled and compared. The model validity was tested with an IS-MIX, Interspiro AB rebreather using a metabolic simulator connected to a breathing machine inside a water-filled pressure chamber. The testing schedule ranged from 0.5-liter (L) to 3-liter tidal volumes, breathing frequencies from five to 25 breaths/minute and oxygen consumptions from 0.5 L/minute to 4 L/minute. Tests were carried out at surface and pressure profiles ranging to 920 kPa(a) (81 meters of sea water, 266 feet of sea water). The root mean squared error (RMSE) of the single-compartment model was 2.4 percent-units of oxygen for the surface test with the 30% dosage setting but was otherwise below 1% unit. For the multicompartment model the RMSE was below 1% unit of oxygen for all tests. It is believed that these models will aid divers in operational settings and may constitute a helpful tool when developing semi-closed rebreathing apparatuses.

  • 42.
    Frånberg, Oskar
    et al.
    KTH, School of Technology and Health (STH), Environmental Physiology.
    Linden, J.
    Gennser, Mikael
    KTH, School of Technology and Health (STH), Environmental Physiology.
    Evaluating a simplified purge procedure for oxygen/nitrox switch rebreathers2011Conference paper (Refereed)
  • 43.
    Frånberg, Oskar
    et al.
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Loncar, Mario
    Larsson, Åke
    Gennser, Mikael
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Örnhagen, Hans
    Metsim, ett hjälpmedel för att testa slutna andningsapparater på ett fysiologiskt sätt2013In: Hygiea, 2013Conference paper (Refereed)
    Abstract [sv]

    Valet av propen som bränsle och de tekniska svårigheter som övervanns för att skapa en säker ämnesomsättningssimulator som kan användas vid tester i tryck motsvarande 100 m dykdjup.

  • 44.
    Frånberg, Oskar
    et al.
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Silvanus, M
    Rebreather technology and practical tests2014Conference paper (Refereed)
  • 45.
    Gennser, Mikael
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Application of ultrasound techniques in diving research: Use of bubble detection to develop trimix tables for Swedish mine-clearance divers and evaluating trimix decompressions2015Conference paper (Refereed)
  • 46.
    Gennser, Mikael
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Problems with introducing the new USN air diving tables for the Swedish Navy.2016Conference paper (Refereed)
  • 47.
    Gennser, Mikael
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Submarine escape physiology2013Conference paper (Refereed)
  • 48.
    Gennser, Mikael
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Testing of decompression tables and use of decompression algorithms: a pragmatic view2014Conference paper (Refereed)
  • 49.
    Gennser, Mikael
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Trimix tables for semi-closed mechanical rebreather: IS-Mix2013Conference paper (Refereed)
  • 50.
    Gennser, Mikael
    et al.
    KTH, School of Technology and Health (STH), Environmental Physiology.
    Bergh, Ulf
    Metoder för effektivare utprovning av dekompressionstabeller för dykning2011Conference paper (Refereed)
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