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  • 1. Amon, M.
    et al.
    Debevec, T.
    Keramidas, Michail E.
    Pisot, R.
    Simunic, B.
    Kounalakis, S.N.
    Mekjavic, I.B.
    Effect of intermittent normobaric hypoxic exposure on performance in hypoxic and normoxic environments2008Conference paper (Other academic)
  • 2. Amon, M.
    et al.
    Debevec, T.
    Keramidas, Michail E.
    Simunic, B.
    Pisot, R.
    Kounalakis, S.N.
    Eiken, O.
    Mekjavic, I.B.
    Intermittent hypoxic training2008Conference paper (Other academic)
  • 3. Amon, M.
    et al.
    Keramidas, Michail E.
    Debevec, T
    Kounalakis, S.N.
    Mekjavic, I.B.
    The effect of hypoxic training regimens on pulmonary function2009Conference paper (Other academic)
  • 4. 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)
  • 5.
    Amon, M.
    et al.
    Jozef Stefan Institute.
    Keramidas, Michail E.
    Jozef Stefan Institute, Slovenia .
    Kounalakis, S.N.
    Hellen Mil Univ, Human Performance Rehabil Lab.
    Mekjavic, I.B.
    Jozef Stefan Institute.
    The effect of a sleep high-train low regimen on the finger cold-induced vasodilation response2012In: High Altitude Medicine & Biology, ISSN 1527-0297, E-ISSN 1557-8682, Vol. 13, no 1, p. 32-39Article in journal (Refereed)
    Abstract [en]

    The present study evaluated the effect of a sleep high-train low regimen on the finger cold-induced vasodilation (CIVD) response. Seventeen healthy males were assigned to either a control (CON; n=9) or experimental (EXP; n=8) group. Each group participated in a 28-day aerobic training program of daily 1-h exercise (50% of peak power output). During the training period, the EXP group slept at a simulated altitude of 2800 meters (week 1) to 3400 m (week 4) above sea level. Normoxic (CIVD(NOR); CON and EXP groups) and hypoxic (CIVD(HYPO); F(I)O(2)=0.12; EXP group only) CIVD characteristics were assessed before and after the training period during a 30-min immersion of the hand in 8°C water. After the intervention, the EXP group had increased average finger skin temperature (CIVD(NOR): +0.5°C; CIVD(HYPO): +0.5°C), number of waves (CIVD(NOR): +0.5; CIVD(HYPO): +0.6), and CIVD amplitude (CIVD(NOR): +1.5°C; CIVD(HYPO): +3°C) in both CIVD tests (p<0.05). In contrast, the CON group had an increase in only the CIVD amplitude (+0.5°C; p<0.05). Thus, the enhancement of aerobic performance combined with altitude acclimatization achieved with the sleep high-train low regimen contributed to an improved finger CIVD response during cold-water hand immersion in both normoxic and hypoxic conditions.

  • 6. 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.

  • 7. 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.
    The use of live low – train high protocol for the enhancement of endurance performance and aerobic capacity.2009Conference paper (Other academic)
  • 8. Debevec, T.
    et al.
    Amon, M.
    Keramidas, Michail E.
    KTH, School of Technology and Health (STH), Environmental Physiology (Closed 20130701).
    Simunic, B.
    Pisot, R.
    Kounalakis, S.N.
    Eiken, O.
    Mekjavic, I.B.
    “Sleep high – train low” altitude training2008Conference paper (Other academic)
  • 9. 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, p. 387-393Article 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.

  • 10. Debevec, T
    et al.
    Keramidas, Michail E.
    KTH, School of Technology and Health (STH), Environmental Physiology (Closed 20130701).
    Amon, M
    Kounalakis, S.N.
    Mekjavic, I.B.
    Evaluation of training protocols for the improvement of altitude and sea level performance2009Conference paper (Other academic)
  • 11. Debevec, T.
    et al.
    Keramidas, Michail E.
    Norman, B
    Gustafsson, T
    Eiken, Ola
    KTH, School of Technology and Health (STH), Environmental Physiology (Closed 20130701).
    Mekjavic, I
    No evidence for the “normobaric oxygen paradox”2011In: Medicine & Science in Sports & Exercise, ISSN 0195-9131, Vol. 43, no S5, p. 151-151Article in journal (Other academic)
  • 12. 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, p. 1059-1065Article 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.

  • 13.
    Eiken, Ola
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Environmental Physiology.
    Keramidas, Michail E
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Environmental Physiology.
    Sköldefors, Håkan
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Environmental Physiology.
    Kölegård, Roger
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Environmental Physiology.
    EFFEKTER AV 5-VECKORS G-TRÄNING PÅ RELAXERAD G-TOLERANS OCH KARDIOVASKULÄR REGLERING2018In: Proceedings from Swedish Aeronautical Medical Society, Annual Scientific Meeting, 2018 / [ed] Claes Bothin, 2018Conference paper (Refereed)
  • 14.
    Eiken, Ola
    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.
    Taylor, Nigel A S
    Grönkvist, Mikael
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Intraocular pressure and cerebral oxygenation during prolonged headward acceleration2017In: European Journal of Applied Physiology, ISSN 1439-6319, E-ISSN 1439-6327, Vol. 117, no 1, p. 61-72Article in journal (Refereed)
    Abstract [en]

    Supra-tolerance head-to-foot directed gravitoinertial load (+Gz) typically induces a sequence of symptoms/signs, including loss of: peripheral vision-central vision-consciousness. The risk of unconsciousness is greater when anti-G-garment failure occurs after prolonged rather than brief exposures, presumably because, in the former condition, mental signs are not consistently preceded by impaired vision. The aims were to investigate if prolonged exposure to moderately elevated +Gz reduces intraocular pressure (IOP; i.e., improves provisions for retinal perfusion), or the cerebral anoxia reserve. Subjects were exposed to 4-min +Gz plateaux either at 2 and 3 G (n = 10), or at 4 and 5 G (n = 12). Measurements included eye-level mean arterial pressure (MAP), oxygenation of the cerebral frontal cortex, and at 2 and 3 G, IOP. IOP was similar at 1 (14.1 +/- 1.6 mmHg), 2 (14.0 +/- 1.6 mmHg), and 3 G (14.0 +/- 1.6 mmHg). During the G exposures, MAP exhibited an initial prompt drop followed by a partial recovery, end-exposure values being reduced by ae<currency>30 mmHg. Cerebral oxygenation showed a similar initial drop, but without recovery, and was followed by either a plateau or a further slight decrement to a minimum of about -14 mu M. Gz loading did not affect IOP. That cerebral oxygenation remained suppressed throughout these G exposures, despite a concomitant partial recovery of MAP, suggests that the increased risk of unconsciousness upon G-garment failure after prolonged +Gz exposure is due to reduced cerebral anoxia reserve.

  • 15.
    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)
  • 16.
    Eiken, Ola
    et al.
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    McDonnell, Adam C.
    Keramidas, Michail E.
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Kölegård, Roger
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Lind, Britta
    KTH, School of Technology and Health (STH), Medical Engineering, Medical Imaging.
    Mekjavic, Igor B.
    Lunar habitat simulation2013Conference paper (Other academic)
  • 17. Geladas, N.D.
    et al.
    Anastassopoulos, S.
    Keramidas, Michail E.
    Koskolou, M.D.
    Maximal oxygen uptake may be limited by sensation of muscle oxygenation2010In: Open Sports Medicine Journal, ISSN 1874-3870, Vol. 4, p. 9-16Article in journal (Refereed)
    Abstract [en]

    Background: The aim of the present study was to investigate the effects of restricted muscular oxygenation on VO2max, peak power output (PPO), and maximum heart rate (HRmax).

    Methods: Six young healthy male subjects participated in four testing sessions within a 2-week period. On four separate days, participants performed stepwise incremental exercise tests to exhaustion (VO2maxNor) on a cycle ergometer under control condition and with thigh cuffs inflated to external pressure of 60, 90 and 120 mmHg, respectively (Cuff60, Cuff90, Cuff120), following a counterbalanced order. Respiratory gas exchange responses, heart rate and near infrared spectroscopy (NIRS) measurements of muscle oxygenation from rectus femoris muscle were continuously monitored during the four tests.

    Results: A decrease proportional to the degree of cuff inflation was observed in VO2max (Nor = 42.9 ± 3.7, Cuff60 = 34.5 ± 5.8, Cuff90 = 33.4 ± 3.5, Cuff120 = 31.2 ± 6.8 ml·kg-1·min-1; p<0.05). Lower values of PPO (Nor= 298 ± 64, Cuff60 = 252 ± 35, Cuff90 = 213 ± 26, Cuff120 = 210 ± 20 Watts, P<0.05) and HRmax (Nor = 183.7 ± 4.8, Cuff60 = 177.5 ± 7.7, Cuff90 = 168.8 ± 14.0, Cuff120 = 170.8 ± 17.1 beats·min-1, p<0.05) were recorded in cuff conditions. Final values of muscle deoxygenation and rate of perceived exertion were not different among the four conditions.

    Conclusions: It appears that with cuff application, muscle oxygenation is compromised leading to premature sensation of maximum effort, which in turn prevents the heart and the muscle from attaining their maximum capacity.

  • 18. Geladas, N.D.
    et al.
    Keramidas, Michail E.
    Performance tests: Laboratory fake or scientific reality?2005Conference paper (Other academic)
  • 19. Geladas, N.D.
    et al.
    Keramidas, Michail E.
    Anastassopoulos, S.N.
    Koskolou, M
    Maximal oxygen uptake may be limited by sensation of muscle oxygenation2006In: Applied Physiology, Nutrition and Metabolism, ISSN 1715-5312, E-ISSN 1715-5320, Vol. 31, p. S30-S30Article in journal (Refereed)
  • 20.
    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.

  • 21.
    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)
  • 22.
    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.
    Taylor, Nigel 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.
    Intraocular pressure and cerebral oxygenation during prolonged headward acceleration2014Conference paper (Refereed)
  • 23.
    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)
  • 24.
    Keramidas, Michail E.
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Effects of acute and long-term hypoxia on local cold tolerance2016Conference paper (Refereed)
    Abstract [en]

    Exposure to high altitude is commonly considered a predisposing factor for local cold injury. A number of field studies have indeed confirmed that local cold tolerance is impaired in low-oxygen environments, presumably due to hypoxia-induced cutaneous vasoconstriction. However, during acute and long-term high-altitude exposure, the hypoxic stressor typically co-exists with other environmental and behavioral components, viz. hypothermia, malnutrition and physical fatigue, which independently or interactively may affect peripheral blood-flow responses. Laboratory-based, control studies have demonstrated that acute exposure to hypoxia, isolated from other confounding factors, does not potentiate vasoconstriction during local cold stress, but delays spontaneous rewarming following such cold stress. Conversely, it appears that long-term exposure to hypoxia elicits adaptive processes, in particular when the high-altitude acclimatization regimen is combined with physical exercise, that reverse the hypoxia-induced vasoconstriction after local limb cooling. Such adaptive responses do, however, not seem to be transferable to sea-level conditions, i.e. they do not reduce vasoconstriction during normoxic conditions, nor to be homogeneous across the limbs.

  • 25.
    Keramidas, Michail E.
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Local cold tolerance: acute hypoxia and hypoxic acclimation2014Conference paper (Refereed)
  • 26. Keramidas, Michail E.
    Muscle and cerebral oxygenation after short-term respiratory work2010Conference paper (Other academic)
  • 27.
    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)
  • 28. Keramidas, Michail E.
    et al.
    Amon, M
    Kounalakis, S.N.
    Mekjavic, I.B.
    Enhancement of the finger cold-induced vasodilatation response with exercise training.2009Conference paper (Refereed)
  • 29.
    Keramidas, Michail E.
    et al.
    JOZEF STEFAN INSTITUTE.
    Debevec, T
    Amon, M
    Kounalakis, S.N.
    Mekjavic, I.B.
    The effect of endurance respiratory muscle training on normoxic and hypoxic performance.2009Conference paper (Refereed)
  • 30.
    Keramidas, Michail E.
    et al.
    Jozef Stefan Institute, Slovenia; Jozef Stefan International Postgraduate School, Slovenia .
    Debevec, T
    Amon, M
    Kounalakis, S.N.
    Simunic, B
    Mekjavic, I.B.
    Respiratory muscle endurance training: Effect on normoxic and hypoxic exercise performance2010In: European Journal of Applied Physiology, ISSN 1439-6319, E-ISSN 1439-6327, Vol. 108, no 4, p. 759-769Article in journal (Refereed)
    Abstract [en]

    The aim of this study was to investigate the effect of respiratory muscle endurance training on endurance exercise performance in normoxic and hypoxic conditions. Eighteen healthy males were stratified for age and aerobic capacity; and randomly assigned either to the respiratory muscle endurance training (RMT = 9) or to the control training group (CON = 9). Both groups trained on a cycle-ergometer 1 h day(-1), 5 days per week for a period of 4 weeks at an intensity corresponding to 50% of peak power output. Additionally, the RMT group performed a 30-min specific endurance training of respiratory muscles (isocapnic hyperpnea) prior to the cycle ergometry. Pre, Mid, Post and 10 days after the end of training period, subjects conducted pulmonary function tests (PFTs), maximal aerobic tests in normoxia ((V) over dotO(2max)NOR), and in hypoxia ((V) over dotO(2max)HYPO; F(I)O(2) = 0.12); and constant-load tests at 80% of (V) over dotO(2max)NOR in normoxia (CLT(NOR)), and in hypoxia (CLT(HYPO)). Both groups enhanced (V) over dotO(2max)NOR (CON: +13.5%; RMT: +13.4%), but only the RMT group improved (V) over dotO(2max)HYPO Post training (CON: -6.5%; RMT: +14.2%). Post training, the CON group increased peak power output, whereas the RMT group had higher values of maximum ventilation. Both groups increased CLT(NOR) duration (CON: +79.9%; RMT: +116.6%), but only the RMT group maintained a significantly higher CLT(NOR) 10 days after training (CON: +56.7%; RMT: +91.3%). CLT(HYPO) remained unchanged in both groups. Therefore, the respiratory muscle endurance training combined with cycle ergometer training enhanced aerobic capacity in hypoxia above the control values, but did not in normoxia. Moreover, no additional effect was obtained during constant-load exercise.

  • 31. Keramidas, Michail E.
    et al.
    Debevec, T.
    Amon, M.
    Simunic, B.
    Pisot, R.
    Kounalakis, S.N.
    Eiken, Ola
    Mekjavic, I.B.
    Respiratory muscle training2008Conference paper (Other academic)
  • 32.
    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)
  • 33.
    Keramidas, Michail E.
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Swedish Aerospace Physiology Centre, SAPC. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Environmental Physiology.
    Gadefors, Magnus
    Mil Acad Karlberg, Stockholm, Sweden..
    Nilsson, Lars-Ove
    Mil Acad Karlberg, Stockholm, Sweden..
    Eiken, Ola
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Swedish Aerospace Physiology Centre, SAPC. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Environmental Physiology.
    Physiological and psychological determinants of whole-body endurance exercise following short-term sustained operations with partial sleep deprivation2018In: European Journal of Applied Physiology, ISSN 1439-6319, E-ISSN 1439-6327, Vol. 118, no 7, p. 1373-1384Article in journal (Refereed)
    Abstract [en]

    The study examined the effects of short-term field-based military training with partial sleep deprivation on whole-body endurance performance in well-trained individuals. Before and after a 2-day sustained operations (SUSOPS), 14 cadets performed a 15-min constant-load cycling at 65% of peak power output (PPO; CLT65), followed by an exhaustive constant-load trial at 85% of PPO (CLT85). Physiological [oxygen uptake (O-2), heart rate (HR), mean arterial pressure (MAP), cardiac output (CO), and regional oxygenation (TOI) in the frontal cerebral cortex and vastus lateralis muscle] and psychological [effort perception (RPE), affective valence (FS), and perceived activation (FAS)] variables were monitored during exercise. SUSOPS reduced time to exhaustion in CLT85 by 29.1% (p = 0.01). During the CLT65 trial, SUSOPS potentiated the exercise-induced elevations in O-2 and HR (p < 0.05), and blunted MAP (p = 0.001). CO did not differ between trials. Yet, towards the end of both CLT85 trials, CO tended to decline (p 0.08); a response that occurred at an earlier stage in the SUSOPS trial. During CLT65, SUSOPS altered neither cerebral nor muscle TOI. The SUSOPS CLT85 trial, however, was terminated at similar leg-muscle deoxygenation (p > 0.05) and lower prefrontal cortex deoxygenation (p < 0.01). SUSOPS increased RPE at submaximal intensities (p = 0.05), and suppressed FAS and FS throughout (p < 0.01). The present findings indicate, therefore, that a brief period of military sustained operations with partial sleep deprivation augment cardiorespiratory and psychological strain, limiting high-intensity endurance capacity.

  • 34. Keramidas, Michail E.
    et al.
    Geladas, N.D.
    Performance Tests: Design and Analysis2008In: Hellenic Journal of Physical Education and Sport, Vol. 69, p. 48-67Article in journal (Refereed)
  • 35. Keramidas, Michail E.
    et al.
    Geladas, N.D.
    Performance Tests: “Detecting the change”2008In: Hellenic Journal of Physical Education and Sport, Vol. 69, p. 14-24Article, review/survey (Refereed)
  • 36. Keramidas, Michail E.
    et al.
    Geladas, N.D.
    Training load: how enough is the enough?2005Conference paper (Other academic)
  • 37.
    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.

  • 38. 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)
  • 39. 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)
  • 40. 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.

  • 41. Keramidas, Michail E.
    et al.
    Kounalakis, S.N.
    Anastassopoulos, S.
    Nassis, G.P.
    Koskolou, M.
    Geladas, N.D.
    The effect of high-intensity interval training combined with application of external pressure on thighs on peak power output2006Conference paper (Refereed)
  • 42.
    Keramidas, Michail E.
    et al.
    Jozef Stefan Institute, Slovenia.
    Kounalakis, S.N.
    Geladas, N.D.
    The effect of interval training combined with external pressure on thighs on maximal and submaximal performance2009In: Acta Physiologica, ISSN 1748-1708, E-ISSN 1748-1716, Vol. 197, no S675, p. L47-L47Article in journal (Refereed)
    Abstract [en]

    It is well known that a moderate reduction of muscle blood flow (low body positive pressure of 50 mmHg) during endurance continuous exercise training enhances the local aerobic muscle adaptations. The present study investigates the effect of interval training combined with thigh cuffs pressure of +90 mmHg on maximal and submaximal performance. Twenty untrained individuals (age = 23.0 ± 4.2 yrs; stature = 168.3 ± 9.6 cm; body mass = 64.2 ± 15.0 kg) were assigned either to control (CON) or to experimental (CUFF) training group. All participants carried out an incremental exercise test to exhaustion (VO2max), a 6-min constant test at 80% of VO2max (Sub80) and a constant power test (TF150) pre and post training. Furthermore, they obtained an incremental exercise test with cuffs inflated to external pressure of +90 mmHg (VO2maxPress) pre-training in order to be determined the training intensity. Both groups performed interval training on cycle-ergometers 3 d·wk-1 for 6 wks. The CON group trained on cycle ergometer without cuffs, whereas the CUFF group trained with cuffs on thighs pressurized to +90 mmHg (cuffs depressurized during active recovery) at the same relative intensity. In particular, each training session consisted of 2-min work bout at 90% of VO2max or VO2maxPress: 2-min active recovery bout at 40% of VO2max. Despite the unchanged VO2max, both groups increased significant PPO (CON: Pre = 207.2 ± 60.6 Watts, Post = 237.7 ± 77.2 Watts; CUFF: Pre = 182.3 ± 40.8 Watts, Post = 227.0 ± 37.7 Watts; P<= 0.05) that was accompanied by higher deoxygenation (DStO2) (CON: Pre = -15.3 ± 1.3%, Post = -29.1 ± 1.3%; CUFF: Pre = -21.6 ± 1.5%, Post = -42.4 ± 1.6%; P<= 0.05) measured with near infrared spectroscopy (NIRS); the deoxygenation was more pronounced on CUFF group (P<= 0.05) at the same relative PPO. Moreover, both groups reduced VO2 (P<= 0.05) during Sub80 without concomitant changes in DStO2. Also, CON and CUFF group improved TF150 by ~40% and ~32%, respectively; but there were no differences between training groups. It seems that 6-wks interval training combined with thigh cuffs pressure of +90 mmHg on exercised legs at the same relative intensity does not provide any additive effect on maximal and submaximal performance. However, despite the lower absolute training intensity of CUFF group, the enhanced PPO that was accompanied by higher DStO2 may reveal improvement of peripheral aerobic factors transferring and consuming O2.

  • 43.
    Keramidas, Michail E.
    et al.
    National and Kapodistrian University of Athens, Greece; Jozef Stefan Institute, Slovenia.
    Kounalakis, S.N.
    Hellenic Military University, Greece.
    Geladas, N.D.
    National and Kapodistrian University of Athens, Greece.
    The effect of interval training combined with thigh cuffs pressure on maximal and submaximal exercise performance2012In: Clinical Physiology and Functional Imaging, ISSN 1475-0961, E-ISSN 1475-097X, Vol. 32, no 3, p. 205-213Article in journal (Refereed)
    Abstract [en]

    The purpose of the study was to investigate the effect of interval training combined with a thigh cuffs pressure of +90 mmHg on maximal and submaximal cycling performance. Twenty untrained individuals were assigned either to a control (CON) or to an experimental (CUFF) training group. Both groups trained 3 days per week for 6 weeks at the same relative intensity; each training session consisted of 2-min work bout at 90% of VO(2max): 2-min active recovery bout at 50% of VO(2max). An incremental exercise test to exhaustion, a 6-min constant-power test at 80% of VO(2max) (Sub(80)) and a maximal constant-power test to exhaustion (TF(150)) were performed pre- and post-training. Despite the unchanged VO(2max), both groups significantly increased peak power output (CON: ∼12%, CUFF: ∼20%) that was accompanied by higher deoxygenation (ΔStO(2)) measured with near-infrared muscle spectroscopy. These changes were more pronounced in the CUFF group. Moreover, both groups reduced VO(2) during the Sub(80) test without concomitant changes in ΔStO(2). TF(150) was enhanced in both groups. Thus, an interval exercise training protocol under moderate restricted blood flow conditions does not provide any additive effect on maximal and submaximal cycling performance. However, it seems to induce peripheral muscular adaptations, despite the lower absolute training intensity.

  • 44.
    Keramidas, Michail E.
    et al.
    Jozef Stefan International Postgraduate School, Slovenia .
    Kounalakis, S.N.
    Mekjavic, I.B.
    Aerobic exercise training preceded by respiratory muscle endurance training: a synergistic action enhances the hypoxic aerobic capacity2011In: European Journal of Applied Physiology, ISSN 1439-6319, E-ISSN 1439-6327, Vol. 111, no 10, p. 2629-2630Article in journal (Refereed)
  • 45.
    Keramidas, Michail E.
    et al.
    University of Athens, Greece.
    Kounalakis, S.N.
    Nassis, G.P.
    Koskolou, M.
    Geladas, N.D.
    Effect of high-intensity interval training on maximal and submaximal performance2006Conference paper (Refereed)
  • 46. 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.

  • 47.
    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.

  • 48.
    Keramidas, Michail E.
    et al.
    KTH, School of Technology and Health (STH), Environmental Physiology.
    Kounalakis, Stylianos N.
    Geladas, Nickos D.
    Eiken, Ola
    KTH, School of Technology and Health (STH), Environmental Physiology.
    Mekjavic, Igor B.
    Heterogeneous sensitivity of cerebral and muscle tissues to acute normobaric hyperoxia at rest2012In: Microvascular Research, ISSN 0026-2862, E-ISSN 1095-9319, Vol. 84, no 2, p. 205-210Article in journal (Refereed)
    Abstract [en]

    The purpose was to investigate the effects of acute normobaric hyperoxia at rest on cerebral, respiratory and leg muscle oxygenation. Ten healthy men were studied twice in a single-blinded counterbalanced crossover study protocol. On one occasion they breathed air and on the other 100% normobaric O-2 for a 2-hour time period. Oxygenated (Delta[O(2)Hb]), deoxygenated (Delta[HHb]) and total (Delta[tHb]) hemoglobin in the cerebral frontal cortex, and in the intercostal and vastus lateralis muscles were simultaneously monitored with near-infrared spectroscopy. The hyperoxic stimulus promptly increased Delta[O(2)Hb] (similar to 2 mu M) and decreased Delta[HHb] (similar to 3.6 mu M) in the frontal cortex. These cerebral responses were directly and fully countered by resumption of normoxic air breathing. In contrast, Delta[HHb] significantly decreased due to the acute hyperoxic stimulus in both intercostal and vastus lateralis muscles. The temporal changes in muscle oxygenation were slower compared to those in the cerebral area; and they only partially recovered during the 15-min normoxic-recovery period. Acute supplementation of normobaric O-2 at rest influences cerebral, leg and respiratory muscle oxygenation of healthy individuals, but not in the same manner. Namely, the frontal cortex seems to be more sensitive to hyperoxia than are the skeletal muscle regions.

  • 49.
    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.

  • 50.
    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.

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