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  • 51.
    Gennser, Mikael
    et al.
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Blogg, L
    Effect of gas switch on decompression from trimix dives2015Conference paper (Refereed)
  • 52.
    Gennser, Mikael
    et al.
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Blogg, L
    Venous gas bubble load after trimix dives using electronic closed circuit rebreathers2014Conference paper (Refereed)
  • 53.
    Gennser, Mikael
    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.
    Blogg, 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.
    Jaki Mekjavic, P
    Mekjavic, IB
    Comparison of venous bubbles and tear film bubbles after decompression during a five week 6° head-down tilt bed rest2015Conference paper (Refereed)
  • 54.
    Gennser, Mikael
    et al.
    KTH, School of Technology and Health (STH), Environmental Physiology.
    Blogg, L.
    Eiken, Ola
    KTH, School of Technology and Health (STH), Environmental Physiology.
    Mekjavic, I.
    Comparison between mild dehydration and body temperature on decompression bubble formation2010Conference paper (Refereed)
  • 55.
    Gennser, Mikael
    et al.
    KTH, School of Technology and Health (STH), Environmental Physiology.
    Blogg, L.
    Frånberg, Oskar
    KTH, School of Technology and Health (STH), Environmental Physiology.
    Bubble recordings after nitrox dives with a semi-closed demand controlled rebreather2011Conference paper (Refereed)
  • 56.
    Gennser, Mikael
    et al.
    KTH, School of Technology and Health (STH), Environmental Physiology.
    Blogg, SL
    Bubble scores after diving according to the new USNavy air decompression tables.2017Conference paper (Refereed)
  • 57.
    Gennser, Mikael
    et al.
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Blogg, SL
    Effekt av gasbyte på dekompressionshastighet efter korta trimix dykningar2015Conference paper (Refereed)
  • 58.
    Gennser, Mikael
    et al.
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Blogg, SL
    Douglas, J
    Kvarnström, A
    Oscarsson, N
    Rosén, A
    Påverkar oxygenandning direkt efter dykning bubbelförekomst?2015Conference paper (Refereed)
  • 59.
    Gennser, Mikael
    et al.
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Douglas, J
    High resolution chest CT: Findings with possible bearing on risk for pulmonary barotrauma2013Conference paper (Refereed)
  • 60.
    Gennser, Mikael
    et al.
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Frånberg, Oskar
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Blogg, S. L
    Dekompressionsbelastning vid trimixdykning: Jämförelse mellan dykning med konstant fraktion och konstant partialtryck oxygen2014Conference paper (Refereed)
    Abstract [sv]

    Bakgrund: Användning av trimixgas (O2, N2, och He) tillåter dykning till större djup än med luft eller nitrox. Trots att den här dyktekniken blir alltmer populär bland sk ”tekniska dykare” så visar de få vetenskapliga rapporter som publicerats att trimixdykning ger upphov till rikligt med bubblor i den venösa cirkulationen (Ljubkovic et al 2010). Den här studien genomfördes för att undersöka venös bubbelförekomst efter dykning med konstant oxygenpartialtryck (PO2). Jämförelse gjordes med tidigare mätningar med konstant oxygenfraktion.

    Metoder: Sex försvarsmaktsdykare och en instruktör deltog i dykningar med sluten återandningsapparat där PO2 kontrollerades elektroniskt (eCCR). Dykningarna genomfördes med trimixgas till djup mellan 20 – 100 m. I de flesta fall hölls PO2 konstant vid 1,3 atm. Dekompressionsprofilerna beräknades med VPM-B algoritm. Förekomst av venösa gasbubblor detekterades med hjälp av ultraljuds-Doppler. Mängden bubblor skattades med Kisman-Masurel skalan (KM). Resultaten jämfördes med trimixdykningar (33 – 60 m) som genomförts i våt tryckkammare, men en halvsluten dykapparat som gav dykarna en konstant oxygenfraktion (FO2 27%). Dekompressionerna i dessa dykningar beräknades med en DCAP-algoritm.

     Resultat: Bubbelförekomst hos de 7 dykarna som använde eCCR undersöktes efter totalt 133 dykningar. Ingen bubbelpoäng över KM 3 uppmättes vid något dyk. Sammanlagt 92 dykningar genomfördes med den halvslutna apparaten. Bubbelpoängen i dessa dykningar varierade mellan 0 – 4 (16% av dykningarna >KM III). Efter upprepade dykningar till 70 m med eCCR var median bubbelpoängen KM 2 (n = 11).

    Slutsats: Djupa trimixdykningar med konstant PO2 och dekompressioner beräknade med VPM-B gav upphov till lägre maximal bubbelförekomst än dykningar med konstant oxygenfraktion.

  • 61.
    Gennser, Mikael
    et al.
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Frånberg, Oskar
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Blogg, Samantha L.
    SLB Consulting, Cumbria, Storbritannien.
    Jämförelse mellan olika dekompressionstabeller med hjälp av ultraljudsdoppler2013In: Hygiea, 2013Conference paper (Refereed)
    Abstract [sv]

    Två dekompressionstabeller, en med sk djupa stopp, jämfördes avseende förekomst av bubblor i den centralvenösa cirkulationen. Tabellen med ortodox algoritm orsakade betydligt färre bubblor.

  • 62.
    Gennser, Mikael
    et al.
    KTH, School of Technology and Health (STH), Environmental Physiology.
    Grönkvist, Mikael
    KTH, School of Technology and Health (STH), Environmental Physiology.
    No changes in pulmonary function indices after nitrox saturation dives.2017Conference paper (Refereed)
  • 63.
    Gennser, Mikael
    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.
    Norrbrand, Lena
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Sundblad, Patrik
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Mekjavic, I.B.
    Eiken, Ola
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Effekt av gasdensitet på ventilation och arteriell oxygenmättnad vid normobar och hypobar hypoxi2016Conference paper (Refereed)
  • 64.
    Grönkvist, Mikael
    et al.
    KTH, School of Technology and Health (STH), Environmental Physiology.
    Bergsten, Eddie
    KTH, School of Technology and Health (STH), Environmental Physiology.
    Eiken, Ola
    KTH, School of Technology and Health (STH), Environmental Physiology.
    Loss of pressure in the anti-G system at high G-loads2011Conference paper (Refereed)
  • 65.
    Grönkvist, Mikael
    et al.
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Cihua, U
    Mekjavic, I.B.
    Eiken, Ola
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Heat strain in a helicopter during a simulated desert mission2016Conference paper (Refereed)
  • 66.
    Grönkvist, Mikael
    et al.
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Ciuha, U
    Eiken, Ola
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Mekjavic, I.B.
    The effect of ambient humidity on performance during simulated desert patrols2014Conference paper (Refereed)
  • 67.
    Grönkvist, Mikael
    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.
    Ciuha, U
    Mekjavic, IB
    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.
    Värmebelastning i helikopter vid simulerat ökenuppdrag2015Conference paper (Refereed)
  • 68.
    Grönkvist, Mikael
    et al.
    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.
    Effects of loss of pressure in the anti-G system during a simulated target chase2013Conference paper (Refereed)
  • 69.
    Grönkvist, Mikael
    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.
    Eiken, Ola
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Intraokulärt tryck och oxygenering av hjärnans frontallob under långvarig, måttlig G-belastning i huvud-fot-riktning2013In: Hygiea, 2013Conference paper (Refereed)
    Abstract [sv]

    Bakgrund: Under G-belastning i huvud-fot-riktning (+Gz) faller pilotens artärtryck mellan hjärt- och huvudnivå. Trots att avståndet - och därmed artärtrycksfallet - är större mellan hjärta och hjärnbark än mellan hjärta och ögon, är näthinnan vanligen det organ som tidigast drabbas av kritiskt ischemi vid +Gz-belastning, vilket huvudsakligen anses bero på att artärtrycket måste övervinna ögonbulbens övertryck om ca 10-15 mmHg för att genomblödning av näthinnan skall kunna ske. I en tidigare undersökning fann vi att den symptomsekvens som normalt uppträder efter 3-10 sekunders latensperiod vid förhöjning av G-belastningen från låg till övertrösklig nivå (d.v.s. perifer synfältsinskränkning - central synfältsinskränkning - grumlat medvetande - medvetandeförlust) ofta uteblir om exponeringen för övertrösklig G-nivå föregås av långvarig exponering för måttligt, men tolererbart, förhöjd belastning. Således, då trycket i G-dräkten fjärmades efter 2 minuter vid +Gz-belastning om 5-6 G var risken att drabbas av medvetslöshet mångfalt högre än då G-belastningen höjdes till motsvarande nivå utan trycksättning av G-dräkt. Föreliggande experimentserier genomfördes för att undersöka om den ändrade symptomsekvensen beror på successivt minskande syrereserver i frontalcortex eller på ökande genomblödning av retina (d.v.s. på minskande intraokulärt tryck (IOP)). Metoder: Friska försökspersoner (fp) exponerades för +Gz-belastning om 2 respektive 3 G, under det att IOP mättes (n= 10), samt för 2, 3, 4 och 5 G, under det att förändringar av frontalcortex syreinnehåll (total oxygen index; TOI) mättes (n=13). Under alla betingelser registrerades mättnadsgraden för oxyhemoglobin i kapillärblodet (SpO2). Samtliga mätningar genomfördes då fp använde G-dräkt och de vid 2 och 3 G även utan att fp använde G-dräkt Resultat: IOP påverkades ej nämnvärt av +Gz-belastning. Såväl SpO2 som TOI sjönk successivt under G-exponeringarna, i synnerhet vid 4- och 5-G-nivåerna, då fp bar G-dräkt. Slutsatser: Den successiva minskningen av TOI vid given belastning antas bero på en pulmonell höger-till-vänster shuntning av blod. Resultaten talar för att den ökade incidens G-betingade medvetslöshet då tryck i G-dräkt fjärmas efter långvarig, måttlig belastning beror på successivt minskande cerebral syrereserv, ledande till att medvetslöshet kan uppträda utan att föregås av varningssymtom i form av synfältsbortfall.

  • 70.
    Grönkvist, Mikael
    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.
    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.
    Sundgren, Carl Johan
    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.
    Interaction of anti-G suit and airway pressures on cerebral oxygenation during prolonged headward acceleration.2015Conference paper (Refereed)
  • 71.
    Grönkvist, Mikael
    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.
    Keramidas, Michail
    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.
    Samverkan mellan anti-G-dräkt och övertryck i luftvägarna på cerebral syresättning vid långvarig G-belastning i huvud-fot riktning2015Conference paper (Refereed)
  • 72. Gustafsson, T.
    et al.
    Kölegård, Roger
    KTH, School of Technology and Health (STH), Environmental Physiology.
    Sundblad, Patrik
    KTH, School of Technology and Health (STH), Environmental Physiology.
    Norman, B.
    Eiken, Ola
    KTH, School of Technology and Health (STH), Environmental Physiology.
    Elevations of local intravascular pressures release vasoactive substances in humans2013In: Clinical Physiology and Functional Imaging, ISSN 1475-0961, E-ISSN 1475-097X, Vol. 33, no 1, p. 38-44Article in journal (Refereed)
    Abstract [en]

    The wall stiffness of arteries and arterioles adapts to the long-term demands imposed by local intravascular pressure. We investigated whether substances capable of inducing acute and long-term effects on arterial wall stiffness are released locally into the bloodstream in response to an acute marked increase in local intravascular pressure in the blood vessels of the human arm. Experiments were performed on ten subjects positioned in a pressure chamber with one arm extended through a hole in the chamber door and kept at normal atmospheric pressure. Intravascular pressure was increased in the arm, by a stepwise increase in chamber pressure up to +150 mmHg. Diameter and flow were measured in the brachial artery by Doppler ultrasonography. Blood samples were drawn simultaneously from both arms before, during, immediately after and 2 h after the release of the chamber pressure. Plasma levels of endothelin-1 (ET-1), vascular endothelial growth factor A (VEGF-A), fibroblast growth factor 2 (FGF-2) and angiotensin II (Ang-II) were measured. Elevation of chamber pressure by 150 mmHg increased local arterial distending pressure to about 220260 mmHg, resulting in an increase in brachial artery diameter of 9% and flow of 246%. The pressure stimulus increased the plasma levels of ET-1 and Ang-II, but not of VEGF-A or FGF-2 in the test arm. The local release of the vasoconstrictors ET-1 and Ang-II in response to markedly increased distending pressure may reflect one mechanism behind adaptation to acute and long-term changes in intravascular pressure.

  • 73.
    Halvorsen, Kjartan
    et al.
    KTH, School of Technology and Health (STH), Medical Engineering.
    Eriksson, Martin
    KTH, School of Technology and Health (STH), Medical Engineering.
    Gullstrand, Lennart
    Swedish Sports Confederation.
    Acute Effects Of Reducing Vertical Displacement And Step Frequency On Running Economy2012In: Journal of Strength and Conditioning Research, ISSN 1064-8011, E-ISSN 1533-4287, Vol. 26, no 8, p. 2065-2070Article in journal (Refereed)
    Abstract [en]

    This work studies the immediate effects of altering the vertical displacement of CoM (VD) and step frequency (SF) on the metabolic cost of level treadmill running at 16 km·h on sixteen male runners. Alterations of VD, SF and the product VD SF was induced using a novel feedback system which presents target and current values to the runner by visual or auditory display. Target values were set to 5 and 10% reductions from individual baseline values. Results were expressed as relative changes from baseline values.Alterations led to an increase in metabolic cost in most cases, measured as VO2 uptake per minute and kg body mass. Correlations were weak. Still, linear multiple regression revealed a positive coefficient (0.28) for the relationship between VD SF and VO2. Separate rank correlation tests showed negative correlation (τ = -0.19) between SF and VO2 and positive correlation (τ = -0.16) between VD and VO2. There is a coupling between VD and SF caused by the mechanics of running, hence isolated reduction of either factor was hard to achieve. The linear model also showed a negative coefficient for the relationship between the height of center of mass above ground (CoMh) and VO2.The effect size was small (multiple R-squared 0.07 and 0.12). Still the results indicate that reducing VD SF by reducing vertical displacement can have a positive effect on running economy, but a concurrent reduction in CoMh may reduce or diminish the positive effect. Mid- and long-term effects of altering the technique should also be studied.

  • 74. Helena, C. H.
    et al.
    Jelena, V. M.
    Nataša, R.
    Vito, F.
    Mekjavic, I. B.
    Eiken, Ola
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Robert, Z.
    A new approach to study properties of isolated preadipocytes following in vivo exposure to hypoxia2013In: Proceedings of Life in space for life on earth, 18-22 June 2012, Aberdeen, ESA Communications , 2013Conference paper (Refereed)
    Abstract [en]

    In the present study we developed a novel approach to study the properties of isolated human preadipocytes from subjects exposed to conditions of hypoxia equivalent to an altitude of 4000 m. By using confocal microscopy we studied the expression of dipeptidyl peptidase 4 (DPP4) in preadipocytes from adult normal-weight males. DPP4 is a transmembrane glycoprotein with enzymatic activity that cleaves Nterminal dipeptides from a diverse range of substrates. The activity of DPP4 is implicated in immune response as well as in glucose homeostasis. To gain insights into the pathophysiological role of DPP4 in insulin resistance we here explored DPP4 expression during prolonged exposure to hypoxia, an experimental model of obesity onset. We used here a rapid method to isolate cells from biopsies and immunolabelled them with antibodies. Then cells were prepared for the analysis with confocal microscopy. The results show that a prolonged exposure to hypoxic environment appears to increases the expression of DPP4 on preadipocytes.

  • 75. Jacobs, Robert A.
    et al.
    Meinild Lundby, Anne-Kristine
    Fenk, Simone
    Gehrig, Saskia
    Christoph, Siebenmann
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology. University of Zürich, Switzerland.
    Flück, Daniela
    Kirk, Niels
    Hilty, Matthias P.
    Lundby, Carsten
    Twenty-eight days of exposure to 3,454 m increases mitochondrial volume density in human skeletal muscle2015In: Journal of Physiology, ISSN 0022-3751, E-ISSN 1469-7793, Vol. 594, no 5, p. 1151-1166Article in journal (Refereed)
    Abstract [en]

    The role of hypoxia on skeletal muscle mitochondria is controversial. Studies superimposing exercise training with hypoxic exposure demonstrate an increase in skeletal muscle mitochondrial volume density (MitoVD ) over equivalent normoxic training. In contrast, a reduction in both skeletal muscle mass and MitoVD have been reported following mountaineering expeditions. These observations may however be confounded by negative energy balance, which may obscure the results. Accordingly we sought to examine the effects of high altitude hypoxic exposure on mitochondrial characteristics, with emphasis on MitoVD , while minimizing changes in energy balance. For this purpose, skeletal muscle biopsies were obtained from 9 lowlanders at sea level (Pre) and following 7 (7 Days) and 28 (28 Days) days of exposure to 3454 m. Maximal ergometer power output, whole-body weight and composition, leg lean mass, and skeletal muscle fibre area all remained unchanged following the altitude exposure. Transmission electron microscopy determined intermyofibrillar (IMF) MitoVD was augmented (P = 0.028) by 11.5 ± 9.2% from Pre (5.05 ± 0.9%) to Day 28 (5.61 ± 0.04%). On the contrary, there was no change in subsarcolemmal (SS) MitoVD . As a result total MitoVD (IMF + SS) was increased (P = 0.031) from 6.20 ± 1.5% at Pre to 6.62 ± 1.4% on Day 28 (7.8 ± 9.3%). At the same time no changes in mass-specific respiratory capacities, mitochondrial protein or antioxidant content were found. This study demonstrates that skeletal muscle MitoVD may increase with 28 days acclimation to 3454 m.

  • 76. Jaki Mekjavic, P
    et al.
    Lenassi, E
    Eiken, Ola
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Mekjavic, IB
    Effect of acute hypercapnia during 10-day hypoxic bed rest on posterior eye structures.2016In: Journal of applied physiology, ISSN 8750-7587, E-ISSN 1522-1601, Vol. 120, no 10, p. 1241-1248Article in journal (Refereed)
  • 77. Jaki Mekjavic, P
    et al.
    Lenassi, E
    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 acute hypercapnia during hypoxic bedrest on posterior eye structures in females2015Conference paper (Refereed)
  • 78. Jaki Mekjavic, P.
    et al.
    Lenassi, E.
    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.
    The effect of acute hypercapnia during hypoxic bedrest and confinement on the retina2014Conference paper (Refereed)
  • 79.
    Keramidas, Michail E.
    et al.
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Amon, M.
    Debevec, T.
    Simunic, B.
    Pisot, R.
    Di Prampero, PE
    Mekjavic, I.B.
    Endurance respiratory muscle training: Does it affect performance in normoxia and hypoxia?2007Conference paper (Refereed)
  • 80.
    Keramidas, Michail E.
    et al.
    KTH, School of Technology and Health (STH), Environmental Physiology.
    Eiken, Ola
    KTH, School of Technology and Health (STH), Environmental Physiology.
    Mekjavic, Igor B.
    Prevailing evidence contradicts the notion of a "normobaric oxygen paradox"2012In: European Journal of Applied Physiology, ISSN 1439-6319, E-ISSN 1439-6327, Vol. 112, no 12, p. 4177-4178Article in journal (Refereed)
  • 81.
    Keramidas, Michail E.
    et al.
    KTH, School of Technology and Health (STH), Environmental Physiology (Closed 20130701).
    Geladas, Nickos D.
    Mekjavic, Igor B.
    Kounalakis, Stylianos N.
    Forearm-finger skin temperature gradient as an index of cutaneous perfusion during steady-state exercise2013In: Clinical Physiology and Functional Imaging, ISSN 1475-0961, E-ISSN 1475-097X, Vol. 33, no 5, p. 400-404Article in journal (Refereed)
    Abstract [en]

    The purpose of this study was to examine whether the forearm-finger skin temperature gradient (Tforearm-finger), an index of vasomotor tone during resting conditions, can also be used during steady-state exercise. Twelve healthy men performed three cycling trials at an intensity of similar to 60% of their maximal oxygen uptake for 75min separated by at least 48h. During exercise, forearm skin blood flow (BFF) was measured with a laser-Doppler flowmeter, and finger skin blood flow (PPG) was recorded from the left index fingertip using a pulse plethysmogram. Tforearm-finger of the left arm was calculated from the values derived by two thermistors placed on the radial side of the forearm and on the tip of the middle finger. During exercise, PPG and BFF increased (P<0.001), and Tforearm-finger decreased (P<0.001) from their resting values, indicating a peripheral vasodilatation. There was a significant correlation between Tforearm-finger and both PPG (r=-0.68; P<0.001) and BFF (r=-0.50; P<0.001). It is concluded that Tforearm-finger is a valid qualitative index of cutaneous vasomotor tone during steady-state exercise.

  • 82. Keramidas, Michail E.
    et al.
    Kounalakis, S.
    Debevec, T.
    Norman, B.
    Gustafsson, T.
    Eiken, Ola
    KTH, School of Technology and Health (STH), Environmental Physiology (Closed 20130701).
    Mekjavic, I.
    The effect of acute normobaric hyperoxia on EPO concentration in healthy males2010Conference paper (Refereed)
  • 83. Keramidas, Michail E.
    et al.
    Kounalakis, S.
    Eiken, Ola
    KTH, School of Technology and Health (STH), Environmental Physiology (Closed 20130701).
    Mekjavic, I.
    The effect of 10-days of hypoxia on muscle and cerebral oxygenation during a submaximal performance test2010In: High Altitude Medicine & Biology, ISSN 1527-0297, E-ISSN 1557-8682, Vol. 11, no 3, p. 269-269Article in journal (Refereed)
  • 84. Keramidas, Michail E.
    et al.
    Kounalakis, S. N.
    Debevec, T.
    Norman, B.
    Gustafsson, T.
    Eiken, Ola
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Mekjavic, I. B.
    Acute normobaric hyperoxia transiently attenuates plasma erythropoietin concentration in healthy males: evidence against the 'normobaric oxygen paradox' theory2011In: Acta Physiologica, ISSN 1748-1708, E-ISSN 1748-1716, Vol. 202, no 1, p. 91-98Article in journal (Refereed)
    Abstract [en]

    Aim: The purpose of the present study was to evaluate the 'normobaric oxygen paradox' theory by investigating the effect of a 2-h normobaric O(2) exposure on the concentration of plasma erythropoietin (EPO). Methods: Ten healthy males were studied twice in a single-blinded counterbalanced crossover study protocol. On one occasion they breathed air (NOR) and on the other 100% normobaric O(2) (HYPER). Blood samples were collected Pre, Mid and Post exposure; and thereafter, 3, 5, 8, 24, 32, 48, 72 and 96 h, and 1 and 2 weeks after the exposure to determine EPO concentration. Results: The concentration of plasma erythropoietin increased markedly 8 and 32 h after the NOR exposure (approx. 58% and approx. 52%, respectively, P < 0.05) as a consequence of its natural diurnal variation. Conversely, the O(2) breathing was followed by approx. 36% decrement of EPO 3 h after the exposure (P < 0.05). Moreover, EPO concentration was significantly lower in HYPER than in the NOR condition 3, 5 and 8 h after the breathing intervention (P < 0.05). Conclusion: In contrast to the 'normobaric oxygen paradox' theory, the present results indicate that a short period of normobaric O(2) breathing does not increase the EPO concentration in aerobically fit healthy males. Increased O(2) tension suppresses the EPO concentration 3 and 5 h after the exposure; thereafter EPO seems to change in a manner consistent with natural diurnal variation.

  • 85. Keramidas, Michail E.
    et al.
    Kounalakis, Stylianos N.
    Eiken, Ola
    KTH, School of Technology and Health (STH), Environmental Physiology (Closed 20130701).
    Mekjavic, Igor B.
    Carbon monoxide exposure during exercise performance: muscle and cerebral oxygenation2012In: Acta Physiologica, ISSN 1748-1708, E-ISSN 1748-1716, Vol. 204, no 4, p. 544-554Article in journal (Refereed)
    Abstract [en]

    Aim: To investigate the effect of carbon monoxide (CO) in the inspired air as anticipated during peak hours of traffic in polluted megalopolises on cerebral, respiratory and leg muscle oxygenation during a constant-power test (CPT). In addition, since O2 breathing is used to hasten elimination of CO from the blood, we examined the effect of breathing O2 following exposure to CO on cerebral and muscle oxygenation during a subsequent exercise test under CO conditions. Methods: Nine men participated in three trials: (i) 3-h air exposure followed by a control CPT, (ii) 1-h air and 2-h CO (18.9 ppm) exposure succeeded by a CPT under CO conditions (CPTCO A), and (iii) 2-h CO and 1-h 100% normobaric O2 exposure followed by a CPT under CO conditions (CPTCO B). All exercise tests were performed at 85% of peak power output to exhaustion. Oxygenated (D[O2Hb]), deoxygenated (D[HHb]) and total (D[tHb]) haemoglobin in cerebral, intercostal and vastus lateralis muscles were monitored with near-infrared spectroscopy throughout the CPTs. Results: Performance time did not vary between trials. However, the vastus lateralis and intercostal D[O2Hb] and D[tHb] were lower in CPTCO A than in CPT. During the CPTCO B, the intercostal D[O2Hb] and D[tHb] were higher than in the CPTCO A. There were no differences in cerebral oxygenation between the trials. Conclusion: Inspiration of 18.9 ppm CO decreases oxygenation in the vastus lateralis and serratus anterior muscles, but does not affect performance. Breathing normobaric O2 moderates the CO-induced reductions in muscle oxygenation, mainly in the intercostals, but does not affect endurance.

  • 86.
    Keramidas, Michail E.
    et al.
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Kounalakis, Stylianos N.
    Eiken, Ola
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Mekjavic, Igor B
    Effects of two short-term, intermittent hypoxic training protocols on the finger temperature response to local cold stress2015In: High Altitude Medicine & Biology, ISSN 1527-0297, E-ISSN 1557-8682, Vol. 16, no 3, p. 251-260Article in journal (Refereed)
    Abstract [en]

    Keramidas, Michail E., Stylianos N. Kounalakis, Ola Eiken, and Igor B. Mekjavic. Effects of two short-Term, intermittent hypoxic training protocols on the finger temperature response to local cold stress. High Alt Med Biol 16:251-260, 2015.-The study examined the effects of two short-Term, intermittent hypoxic training protocols, namely exercising in hypoxia and living in normoxia (LL-TH; n=8), and exercising in normoxia preceded by a series of brief intermittent hypoxic exposures at rest (IHE+NOR; n=8), on the finger temperature response during a sea-level local cold test. In addition, a normoxic group was assigned as a control group (NOR; n=8). All groups trained on a cycle-ergometer 1h/day, 5 days/week for 4 weeks at 50% of peak power output. Pre, post, and 11 days after the last training session, subjects immersed their right hand for 30min in 8°C water. In the NOR group, the average finger temperature was higher in the post (+2.1°C) and 11-day after (+2.6°C) tests than in the pre-Test (p≤0.001). Conversely, the fingers were significantly colder immediately after both hypoxic protocols (LL-TH:-1.1°C, IHE+NOR:-1.8°C; p=0.01). The temperature responses returned to the pre-Training level 11 days after the hypoxic interventions. Ergo, present findings suggest that short-Term intermittent hypoxic training impairs sea-level local cold tolerance; yet, the hypoxic-induced adverse responses seem to be reversible within a period of 11 days.

  • 87. Keramidas, Michail E.
    et al.
    Kounalakis, Stylianos N.
    Eiken, Ola
    KTH, School of Technology and Health (STH), Environmental Physiology.
    Mekjavic, Igor B.
    Muscle and cerebral oxygenation during exercise performance after short-term respiratory work2011In: Respiratory Physiology & Neurobiology, ISSN 1569-9048, E-ISSN 1878-1519, Vol. 175, no 2, p. 247-254Article in journal (Refereed)
    Abstract [en]

    The purpose of the study was to investigate the effect of 30-min voluntary hyperpnoea on cerebral, respiratory and leg muscle balance between 02 delivery and utilization during a subsequent constant-power test. Eight males performed a VO2max test, and two exercise tests at 85% of peak power output: (a) a control constant-power test (CPT), and (b) a constant-power test after a respiratory maneuver (CPTRM). Oxygenated (Delta[O(2)Hb]), deoxygenated (Delta[HHb]) and total (Delta[tHb]) hemoglobin in cerebral, intercostal and vastus lateralis were monitored with near-infrared spectroscopy. The performance time dropped similar to 15% in CPTRM (6:55 +/- 2:52 min) compared to CPT (8:03 +/- 2:33 min), but the difference was not statistically significant. The vastus lateral's and intercostal Delta[tHb] and Delta[HHb] were lower in CPTRM than in CPT (P <= 0.05). There were no differences in cerebral oxygenation between the trials. Thus, respiratory work prior to an exercise test influences the oxygenation during exercise in the leg and respiratory muscles, but not in the frontal cortex. (C) 2010 Elsevier B.V. All rights reserved.

  • 88.
    Keramidas, Michail E.
    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.
    Eiken, Ola
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Mekjavic, I.B.
    Prolonged physical inactivity leads to a drop in toe skin temperature during local cold stress2014In: Applied Physiology, Nutrition and Metabolism, ISSN 1715-5312, E-ISSN 1715-5320, Vol. 39, no 3, p. 369-374Article in journal (Refereed)
    Abstract [en]

    The purpose was to examine the effects of a prolonged period of recumbency on the toe temperature responses during cold-water foot immersion. Ten healthy males underwent 35 days of horizontal bed rest. The right foot of the subjects was assigned as the experimental (EXP) foot. To prevent bed rest-induced vascular deconditioning in the left control foot (CON), a sub-atmospheric vascular pressure countermeasure regimen was applied on the left lower leg for 4 x 10 min every second day. On the first (BR-1) and the last (BR-35) day of the bed rest, subjects performed two 30 min foot immersion tests in 8 degrees C water, one with the EXP foot and the other with the CON foot. The tests were conducted in counter-balanced order and separated by at least a 15 min interval. At BR-35, the average skin temperature of the EXP foot was lower than at BR-1 (-0.8 degrees C; P = 0.05), a drop that was especially pronounced in the big toe (-1.6 degrees C; P = 0.05). In the CON foot, the average skin temperature decreased by 0.6 degrees C in BR-35, albeit the reduction was not statistically significant (P = 0.16). Moreover, the pressure countermeasure regimen ameliorated immersion-induced thermal discomfort for the CON foot (P = 0.05). Present findings suggest that severe physical inactivity exaggerates the drop in toe skin temperature during local cold stress, and thus might constitute a potential risk factor for local cold injury.

  • 89.
    Keramidas, Michail E.
    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.
    Mekjavic, I.
    Eiken, Ola
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Acute effects of normobaric hypoxia on hand-temperature responses during and after local cold stress2014In: High Altitude Medicine & Biology, ISSN 1527-0297, E-ISSN 1557-8682, Vol. 15, no 2, p. 183-191Article in journal (Refereed)
    Abstract [en]

    The purpose was to investigate acute effects of normobaric hypoxia on hand-temperature responses during and after a cold-water hand immersion test. Fifteen males performed two right-hand immersion tests in 8 degrees C water, during which they were inspiring either room air (Fio(2): 0.21; AIR), or a hypoxic gas mixture (Fio(2): 0.14; HYPO). The tests were conducted in a counterbalanced order and separated by a 1-hour interval. Throughout the 30-min cold-water immersion (CWI) and the 15-min spontaneous rewarming (RW) phases, finger-skin temperatures were measured continuously with thermocouple probes; infrared thermography was also employed during the RW phase to map all segments of the hand. During the CWI phase, the average skin temperature (Tavg) of the fingers did not differ between the conditions (AIR: 10.2 +/- 0.5 degrees C, HYPO: 10.0 +/- 0.5 degrees C; p = 0.67). However, Tavg was lower in the HYPO than the AIR RW phase (AIR: 24.5 +/- 3.4 degrees C; HYPO: 22.0 +/- 3.8 degrees C; p = 0.002); a response that was alike in all regions of the immersed hand. Accordingly, present findings suggest that acute exposure to normobaric hypoxia does not aggravate the cold-induced drop in hand temperature of normothermic males. Still, hypoxia markedly impairs the rewarming responses of the hand.

  • 90.
    Keramidas, Michail E.
    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.
    Mekjavic, Igor B.
    Eiken, Ola
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    PlanHab: Hypoxia exaggerates the bedrest-induced reduction in peak oxygen uptake during upright cycle-ergometry2016In: American Journal of Physiology. Heart and Circulatory Physiology, ISSN 0363-6135, E-ISSN 1522-1539Article in journal (Refereed)
    Abstract [en]

    The study examined the effects of hypoxia and horizontal bedrest, separately and in combination, on peak oxygen uptake (VO2peak) during upright cycle-ergometry. Ten male lowlanders underwent three 21-day confinement periods, in a counterbalanced order: i) normoxic bedrest (NBR; PIO2 = 133.1 ± 0.3 mmHg), ii) hypoxic bedrest (HBR; PIO2 = 90.0 ± 0.4 mmHg), and iii) hypoxic ambulation (HAMB; PIO2 = 90.0 ± 0.4 mmHg). Before and after each confinement, subjects performed two incremental-load trials to exhaustion, while inspiring either room-air (AIR), or a hypoxic gas (HYPO; PIO2 = 90.0 ± 0.4 mmHg). Changes in regional oxygenation of the vastus lateralis muscle and the frontal cerebral cortex were monitored with near-infrared spectroscopy. Cardiac output (CO) was recorded using a bioimpedance method. The AIR VO2peak was decreased by both HBR (~13.5%; p ≤ 0.001) and NBR (~8.6%; p ≤ 0.001), with greater drop after HBR (p = 0.01). The HYPO VO2peak was also reduced by HBR (-9.7%; p ≤ 0.001) and NBR (-6.1%; p ≤ 0.001). Peak CO was lower after both bedrest interventions, and especially after HBR (HBR: ~13%, NBR: ~7%; p ≤ 0.05). Exercise-induced alterations in muscle and cerebral oxygenation were blunted in a similar manner after both bedrest confinements. No changes were observed in HAMB. Hence, the bedrest-induced decrease in VO2peak was exaggerated by hypoxia, most likely due to a reduction in convective O2 transport, as indicated by the lower peak values of CO.

  • 91.
    Keramidas, Michail E.
    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.
    Chouker, Alexander
    Strewe, Claudia
    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: Hypoxia counteracts the erythropoietin suppression, but seems to exaggerate the plasma volume reduction induced by 3 weeks of bed rest2016In: Physiological Reports, E-ISSN 2051-817X, Vol. 4, no 3Article in journal (Refereed)
    Abstract [en]

    The study examined the distinct and synergistic effects of hypoxia and bed rest on the erythropoietin (EPO) concentration and relative changes in plasma volume (PV). Eleven healthy male lowlanders underwent three 21‐day confinement periods, in a counterbalanced order: (1) normoxic bed rest (NBR; PIO2: 133.1 ± 0.3 mmHg); (2) hypoxic bed rest (HBR; PIO2: 90.0 ± 0.4 mmHg, ambient simulated altitude of ~4000 m); and (3) hypoxic ambulation (HAMB; PIO2: 90.0 ± 0.4 mmHg). Blood samples were collected before, during (days 2, 5, 14, and 21) and 2 days after each confinement to determine EPO concentration. Qualitative differences in PV changes were also estimated by changes in hematocrit and hemoglobin concentration along with concomitant changes in plasma renin concentration. NBR caused an initial reduction in EPO by ~39% (= 0.04). By contrast, HBR enhanced EPO (= 0.001), but the increase was less than that induced by HAMB (< 0.01). All three confinements caused a significant reduction in PV (< 0.05), with a substantially greater drop in HBR than in the other conditions (< 0.001). Thus, present results suggest that hypoxia prevents the EPO suppression, whereas it seems to exaggerate the PV reduction induced by bed rest.

  • 92. Keramidas, Michail E.
    et al.
    Norman, B.
    Gustafsson, T.
    Eiken, Ola
    KTH, School of Technology and Health (STH), Environmental Physiology (Closed 20130701).
    Mekjavic, I.B.
    Enhancement of erythropoiesis with normobaric hyperoxia: a promising treatment turns “anaemic”?2011Conference paper (Refereed)
  • 93. Keramidas, Michail E.
    et al.
    Norman, Barbara
    Gustafsson, Thomas
    Eiken, Ola
    KTH, School of Technology and Health (STH), Environmental Physiology (Closed 20130701).
    Mekjavic, Igor B.
    Long-term intermittent hyperoxic exposures do not enhance erythropoiesis2012In: European Journal of Clinical Investigation, ISSN 0014-2972, E-ISSN 1365-2362, Vol. 42, no 3, p. 260-265Article in journal (Refereed)
    Abstract [en]

    Eur J Clin Invest 2011 ABSTRACT: Background  Based on a report of a marked increase in the erythropoietin concentration ([EPO]) a few hours after the cessation of a single 2-h session of O(2) breathing, short periods of O(2) administration have been advocated as a therapy for anaemia. Accordingly, the purpose of the present study was to evaluate this theory by investigating the effect of 10 daily short-term exposures to normobaric O(2) over a 2-week period on the plasma [EPO] in healthy individuals. Material and methods  Twenty men were assigned to either an experimental (NBO(2) ) or to a control (AIR) group. The NBO(2) group breathed 100% normobaric O(2) for 2 h every weekday over a 2-week period. The AIR group breathed air within the same time protocol. Blood samples were collected at the pre-, mid- and post-intervention periods to determine [EPO]. Results  [EPO] of the NBO(2) group was significantly lower than that of the AIR group during the mid- and post-periods (P < 0·001). [EPO] of the NBO(2) group showed a slight, albeit statistically nonsignificant, decrease during the mid (∼ 11%)- and post (∼ 16%)-periods. Conclusions  Daily short-term exposures to normobaric hyperoxia do not increase the [EPO] in healthy individuals. The increased O(2) tension suppresses [EPO]. Hence, administration of pure O(2) to enhance erythropoiesis is not warranted.

  • 94. Kounalakis, S.
    et al.
    Eiken, Ola
    KTH, School of Technology and Health (STH), Environmental Physiology.
    Mekjavic, I.
    Exercise thermoregulatory responses following a 28-day sleep-high train-low regimen2012In: European Journal of Applied Physiology, ISSN 1439-6319, E-ISSN 1439-6327, Vol. 112, no 11, p. 3881-3891Article in journal (Refereed)
    Abstract [en]

    The potentiated exercise-sweating rate observed during acute hypoxia is diminished after a sleep-high train-low (SH-TL) regimen. We tested the hypothesis that this attenuation of the sweating response after SH-TL is compensated for by an increase in heat loss via vasodilatation. Nine male subjects participated in a 28-day SH-TL regimen. Before (pre-), and after (post-) the SH-TL protocol, they performed an test under normoxia and hypoxia. Additionally, pre- and post-SH-TL they completed three 30-min constant-work rate trials on a cycle ergometer. In one trial, the subjects inspired room air while exercising at 50 % of normoxic (CT). In the remaining trials, subjects exercised in hypoxia (FIO2 12.5 %), either at the same absolute (HAT) or relative (50 % of hypoxic ) work rate (HRT) as in CT. Despite similar exercise core temperature responses between pre- and post-SH-TL trials, sweating rate was potentiated in HAT pre-SH-TL [CT: 1.97 (0.42); HRT: 1.86 (0.31); HAT: 2.55 (0.53) mg cm(-2) min(-1); p < 0.05]. Post-SH-TL exercise sweating rate was increased for CT, and remained unchanged in HRT and HAT [CT: 2.42 (0.76); HRT: 2.01 (0.33); HAT: 2.59 (0.30) mg cm(-2) min(-1)]. Pre-SH-TL, the forearm-fingertip skin temperature difference (Tsk(f-f)) was higher in HAT than in CT and HRT by similar to 3.5A degrees C (p < 0.05). The inter-condition differences in Tsk(f-f) were diminished post-SH-TL. In conclusion, the decrease in sweating rate during hypoxic exercise, following a SH-TL regimen, was countered by an increase in vasodilatation (reduced Tsk(f-f)), whereas SH-TL enhanced the sweating response during normoxic exercise. The mechanisms underlying these SH-TL-induced alterations in thermoregulatory responses remain to be settled.

  • 95. Kounalakis, S.N.
    et al.
    Keramidas, Michail E.
    KTH, School of Technology and Health (STH), Environmental Physiology (Closed 20130701).
    Biolo, G.
    Di Prampero, P.E.
    Narici, M.
    Pisot, R
    Eiken, Ola
    Mekjavic, I.B.
    Thermoregulatory responses to cold water immersion following 35 days of horizontal bed-rest2007Conference paper (Refereed)
  • 96.
    Kounalakis, S.N.
    et al.
    Department of Automation, Biocybernetics and Robotics, Jozef Stefan Institute.
    Keramidas, Michail E.
    KTH, School of Technology and Health (STH), Environmental Physiology (Closed 20130701). Jozef Stefan Institute, Slovenia .
    Eiken, Ola
    KTH, School of Technology and Health (STH), Environmental Physiology (Closed 20130701).
    Jaki Mekjavic, P.
    Eye Hospital, University Clinical Centre Ljubljana.
    Mekjavic, I.B.
    Department of Automation, Biocybernetics and Robotics, Jozef Stefan Institute.
    Peak oxygen uptake and regional oxygenation in response to a 10-day confinement to normobaric hypoxia2013In: Scandinavian Journal of Medicine and Science in Sports, ISSN 0905-7188, E-ISSN 1600-0838, Vol. 23, no 4, p. e233-e245Article in journal (Refereed)
    Abstract [en]

    We investigated the effect of hypoxic acclimatization per se, without any concomitant influence of strenuous physical activity on muscle and cerebral oxygenation. Eight healthy male subjects participated in a crossover-designed study. In random order, they conducted a 10-day normoxic (CON) and a 10-day hypoxic (EXP) confinement. Pre and post both CON and EXP confinements, subjects conducted two incremental-load cycling exercises to exhaustion; one under normoxic, and the other under hypoxic (FIO2 = 0.154) conditions. Oxygen uptake ((V) over dotO(2)), ventilation ((V) over dot E), and relative changes in regional hemoglobin oxygenation (Delta([HbO(2)]) in the cerebral cortex and in the serratus anterior (SA) and vastus lateralis (VL) muscles were measured. No changes were observed in the CON confinement. Peak work rate and (V) over dotO(2peak) were similar pre and post in the EXP confinement, whereas (V) over dot(E) increased in the EXP post normoxic and hypoxic trials (P < 0.05). The exercise-induced drop in VL Delta[HbO(2)] was less in the post-than pre-EXP trial by 4.0 +/- 0.4 and 4.2 +/- 0.6 mMduring normoxic and hypoxic exercise, respectively. No major changes were observed in cerebral or SA oxygenation. These results demonstrate that a 10-day hypoxic exposure without any concomitant physical activity had no effect on normoxic or hypoxic (V) over dotO(2peak), despite the enhanced VL oxygenation.

  • 97.
    Kölegard, Roger
    et al.
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Mekjavic, Igor B.
    Eiken, Ola
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Effects of physical fitness on relaxed G-tolerance and the exercise pressor response2013In: European Journal of Applied Physiology, ISSN 1439-6319, E-ISSN 1439-6327, Vol. 113, no 11, p. 2749-2759Article in journal (Refereed)
    Abstract [en]

    Fighter pilots are commonly recommended strength training as a means of improving the tolerance to withstand high gravitoinertial (G) loads. Previous studies on the effect of short-term strength-training regimens on G-endurance show equivocal results, with a majority of the studies suggesting improved G-endurance. The mechanisms underlying such improvement are unknown. Presumably, any change in G-tolerance induced by physical training habits should be manifest following long-term training. We also reasoned that during repeated straining maneuvers-as during certain G-endurance protocols-the relaxed G-tolerance and the exercise pressure response may play a significant role in maintaining adequate arterial pressure, and hence that different training modalities might alter G-endurance, by altering the exercise pressor response. Three groups of males were studied, long-term (>6 months) endurance-trained (E; n = 17), strength-trained (S; n = 16) and untrained (U; n = 17) individuals. The pressor response was studied during sustained (40 s) isometric knee extensions at 50 % of the maximal contraction level. Relaxed gradual onset-rate G-tolerance was determined. G-tolerance was similar in the E (4.6 +/- 0.5 G), S (4.9 +/- 0.8 G) and U (4.6 +/- 0.8 G) groups. The mean arterial pressure increase during isometric exercise was higher in the S (36 +/- 7 mmHg = mean +/- SD) and U (35 +/- 16 mmHg) groups than in the E group (28 +/- 8 mmHg). The results suggest that relaxed G-tolerance is unaffected by physical training habits, and that the training modality affects the magnitude of the exercise pressor response. However, it seems that the response is blunted by endurance training rather than enhanced by strength training.

  • 98.
    Kölegård, Roger
    et al.
    KTH, School of Technology and Health (STH), Environmental Physiology.
    Eiken, Ola
    KTH, School of Technology and Health (STH), Environmental Physiology.
    Betydelse av in vivo styvhet hos perifera blodkärl ur ett flygmedicinskt perspektiv2011Conference paper (Refereed)
  • 99.
    Kölegård, Roger
    et al.
    KTH, School of Technology and Health (STH), Environmental Physiology.
    Eiken, Ola
    KTH, School of Technology and Health (STH), Environmental Physiology.
    Distensibility in human veins as affected by 5 weeks of repeated elevations of local transmural pressure2011In: European Journal of Applied Physiology, ISSN 1439-6319, E-ISSN 1439-6327, Vol. 111, no 12, p. 3119-3125Article in journal (Refereed)
    Abstract [en]

    The objectives were to investigate the effects of repeated increments in local intravascular pressure (pressure training; PT) on (1) distensibility in two arm veins, and (2) pain in the arm induced by markedly increased intravascular pressure. Elevation of venous distending pressure (DP) in an arm was induced by placing the subject (n = 8) in a pressure chamber with one arm protruding to the outside via a port in the chamber door, and increasing chamber pressure. During 5 weeks, venous DP in one arm was repeatedly (3 × 40 min/week) increased (65-105 mmHg). Pressure-distension relationships were determined in the brachial and cephalic veins by measuring diameter changes by ultrasonography during stepwise increments in DP to 180 mmHg. In the brachial vein, the diameter change in response to an increase in DP from 30 to 180 mmHg (distensibility) was reduced (P < 0.05) in the pressure-trained arm (11%) compared to that in the control arm before (23%) and after (21%) PT. The cephalic vein showed a similar response with a reduced (P < 0.05) distensibility in the pressure-trained arm (20%) compared to that in the control arm before (29%) and after (25%) PT. At any given DP, arm pain was less (P < 0.05) in the pressure-trained arm than in the control arm before and after PT, presumably reflecting the reduced venous distensibility in the pressure-trained arm. The results support the concept that the distensibility of venous walls adapts to meet the demands imposed by the prevailing local transmural pressures.

  • 100.
    Kölegård, Roger
    et al.
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Sundblad, Patrik
    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.
    Eiken, Ola
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Är det möjligt att uppskatta Gz-tolerans medelst ortostatisk prov?2015Conference paper (Refereed)
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