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  • 1. 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)
  • 2. Arvedsen, SK
    et al.
    Eiken, Ola
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology. KTH, School of Technology and Health (STH), Centres, Swedish Aerospace Physiology Centre, SAPC.
    Kölegård, Roger
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology. KTH, School of Technology and Health (STH), Centres, Swedish Aerospace Physiology Centre, SAPC.
    Petersen, L. G.
    Damgaard, M.
    Body height and arterial pressure in seated and supine young males during +2 G centrifugation2015In: American Journal of Physiology. Regulatory Integrative and Comparative Physiology, ISSN 0363-6119, E-ISSN 1522-1490, Vol. 309, no 9Article in journal (Refereed)
    Abstract [en]

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

  • 3. Berg, Ulf
    et al.
    Kölegård, Roger
    KTH, School of Technology and Health (STH), Environmental Physiology.
    Eiken, Ola
    KTH, School of Technology and Health (STH), Environmental Physiology.
    Fysiska tester i samband med Grundläggande militär utbildning (GMU)2012Report (Other academic)
  • 4. Ciuha, U
    et al.
    Grönkvist, Mikael
    KTH, School of Technology and Health (STH), Environmental Physiology.
    Mekjavic, I
    Kölegård, Roger
    KTH, School of Technology and Health (STH), Environmental Physiology.
    Pavlinič, D
    Eiken, Ola
    KTH, School of Technology and Health (STH), Environmental Physiology.
    Thermal strain in soldiers performing patrol missions in a desert climate: effect of two different cooling strategies2011Conference paper (Refereed)
  • 5.
    Eiken, Ola
    et al.
    KTH, School of Technology and Health (STH), Environmental Physiology.
    Grönkvist, Mikael
    KTH, School of Technology and Health (STH), Environmental Physiology.
    Kölegård, Roger
    KTH, School of Technology and Health (STH), Environmental Physiology.
    Danielsson, Ulf
    KTH, School of Technology and Health (STH), Environmental Physiology.
    Zavec, D.
    Kounalakis, S.N.
    Mekjavic, I.
    Termisk belastning hos soldater som bär svensk stridsutrustning2010Report (Other academic)
  • 6.
    Eiken, Ola
    et al.
    KTH, School of Technology and Health (STH), Environmental Physiology.
    Grönkvist, Mikael
    KTH, School of Technology and Health (STH), Environmental Physiology.
    Kölegård, Roger
    KTH, School of Technology and Health (STH), Environmental Physiology.
    Zavec, D.
    Ciuha, U.
    Mekjavic, I.
    Termisk belastning hos markstridssoldater vid patrullering i ökenklimat: effekter av två olika ballistiska kroppsskydd samt av två olika strategier för nedkylning2011Report (Other academic)
  • 7.
    Eiken, Ola
    et al.
    Swedish Defence Research Agency.
    Kolegard, Roger
    Swedish Defence Research Agency.
    Pain in the arms induced by markedly increased intravascular pressure decreases after repeated exposures to moderately increased pressures1999In: Journal of gravitational physiology : a journal of the International Society for Gravitational Physiology, ISSN 1077-9248, Vol. 6, no 1, p. 35-36Article in journal (Refereed)
    Abstract [en]

    It is well documented that exposure to high gravitational (G)-load in the head-to-foot direction may induce arm pain. Such G-induced arm pain is of vascular origin and caused by markedly increased pressure in the arm vessels. It has been hypothesized that the arm pain is due to pressure-induced overdistension of local blood vessels. Indeed, elevation of local intravascular pressure to levels that induce considerable arm pain results in distension of both veins and arteries. There appears to be a paucity of data regarding the effects of repeatedly increasing intravascular pressure in the arms. Accordingly, the purpose of the present study was to investigate the effect of iterative exposures to moderate pressure elevations in the arm vessels (here termed "pressure training") on the pressure distension relationships of the vessels and on pressure-induced arm pain. To experimentally induce increased transmural pressure over the vessel walls of the arms we used a modified version of a method described elsewhere; this method has also proven a useful tool for simulating G-induced arm pain.

  • 8.
    Eiken, Ola
    et al.
    Karolinska Inst, Swedish Def Res Agcy.
    Kolegard, Roger
    Karolinska Inst, Swedish Def Res Agcy.
    Mekjavic, Igor B.
    Jozef Stefan Inst, Dept Automat Biocybernet & Robot.
    Pressure-distension relationship in arteries and arterioles in response to 5 wk of horizontal bedrest2008In: American Journal of Physiology. Heart and Circulatory Physiology, ISSN 0363-6135, E-ISSN 1522-1539, Vol. 295, no 3, p. H1296-H1302Article in journal (Refereed)
    Abstract [en]

    We hypothesized that exposure to prolonged recumbency (bedrest), and thus reductions of intravascular pressure gradients, increases pressure distension in arteries/arterioles in the legs. Ten subjects underwent 5 wk of horizontal bedrest. Pressure distension was investigated in arteries and arterioles before and after the bedrest, with the subject seated or supine in a hyperbaric chamber with either one arm or a lower leg protruding through a hole in the chamber door. Increased pressure in the vessels of the arm/leg was accomplished by increasing chamber pressure. Vessel diameter and flow were measured in the brachial and posterior tibial arteries using Doppler ultrasonography. Electrical tissue impedance was measured in the test limb. Bedrest increased (P < 0.01) pressure distension threefold in the tibial artery (from 8 +/- 7% to 24 +/- 11%) and by a third (P < 0.05) in the brachial artery (from 15 +/- 9% to 20 +/- 10%). The pressure-induced increase in tibial artery flow was more pronounced (P < 0.01) after (50 +/- 39 ml/min) than before (13 +/- 23 ml/min) bedrest, whereas the brachial artery flow response was unaffected by bedrest. The pressure-induced decrease in tissue impedance in the leg was more pronounced (P < 0.01) after (16 +/- 7%) than before (10 +/- 6%) bedrest, whereas bedrest did not affect the impedance response in the arm. Thus, withdrawal of the hydrostatic pressure gradients that act along the blood vessels in erect posture markedly increases pressure distension in dependent arteries and arterioles.

  • 9.
    Eiken, Ola
    et al.
    Swedish Defence Research Agency.
    Kölegärd, Roger
    Swedish Defence Research Agency.
    Bergsten, Eddie
    Swedish Defence Research Agency.
    Grönkvist, Mikael
    Swedish Defence Research Agency.
    G protection: interaction of straining maneuvers and positive pressure breathing2007In: Aviation, Space and Environmental Medicine, ISSN 0095-6562, E-ISSN 1943-4448, Vol. 78, no 4, p. 392-398Article in journal (Refereed)
    Abstract [en]

    INTRODUCTION: G protection in the 39 Gripen aircraft is provided by a full coverage anti-G suit, a pressure-breathing system, and anti-G straining maneuvers (AGSM). The purpose was to study (1) the interaction of pressure breathing and AGSM while wearing an anti-G suit; and (2) the G-protective properties of the anti-G suit alone and in combination with the pressure-breathing system.

    METHODS: During rapid onset rate G-time profiles (< or =9 G), 10 subjects were investigated in 5 conditions: (I) sitting relaxed, without any G-protective garment; (II) sitting relaxed and wearing an anti-G suit; (III) sitting relaxed, wearing an anti-G suit, and pressure breathing; IV) wearing an anti-G suit and performing AGSM; and V) wearing an anti-G suit, pressure breathing, and performing AGSM. In supplementary experiments (n=9), the share of the anti-G suit protection afforded by the abdominal bladder was investigated.

    RESULTS: G tolerance was 3.4 Gz (range: 2.8-4.3) in condition I, > or = 6.5 Gz (4.5-9.0) in II, > or = 8.0 Gz (6.5-9.0) in III, > or = 8.9 Gz (8.5-9.0) in IV and > or = 9.0 Gz (8.5-9.0) in V. In the supplementary experiments, the anti-G suit afforded a 2.8-G protection, a third of which was contributed by the abdominal bladder. In the relaxed state, pressure applied to the airways was transmitted undistorted to the intrathoracic space. During AGSM, intrathoracic pressure rose to 10-14 kPa, regardless of whether AGSM was performed with or without pressure breathing.

    DISCUSSION AND CONCLUSIONS: The anti-G suit and the pressure breathing system provide G protection of > or = 4.6 G, of which the anti-G suit contributes about 3.0 G. The C-protective properties of the anti-G suit and those of pressure breathing appears to be additive, whereas the G protection afforded by pressure breathing does not add to that provided by AGSM.

  • 10.
    Eiken, Ola
    et al.
    Swedish Defence Research Agency, Defence Medicine, Berzelius v. 13, Karolinska Institutet.
    Kölegård, Roger
    Swedish Defence Research Agency, Defence Medicine, Berzelius v. 13, Karolinska Institutet.
    Comparison of vascular distensibility in the upper and lower extremity2004In: Acta Physiologica Scandinavica, ISSN 0001-6772, E-ISSN 1365-201X, Vol. 181, no 3, p. 281-287Article in journal (Refereed)
    Abstract [en]

    Aim: Because of the great differences in hydrostatic pressure acting along the blood vessels in the erect posture, leg vessels are exposed to greater transmural pressures than arm vessels. The in vivo pressure-distension relationship of arteries, arterioles and veins in the arm were compared with those of the leg. Methods: Experiments were performed with the subject (n = 11) positioned in a pressure chamber with an arm or lower leg (test limb) extended at heart level through a hole in the chamber door. Intravascular pressure in the arm/lower leg was increased by stepwise increasing chamber pressure to +180 and +210 mmHg, respectively. Diameters of blood vessels and arterial flow were measured using ultrasonographic/Doppler techniques. Changes in forearm and lower leg volumes were assessed using an impedance technique. The subject rated perceived pain in the test limb. Results: The brachial and radial arteries were found to be more distensible than the posterior tibial artery (P < 0.001). Likewise, the distension was more pronounced in the cephalic than in the great saphenous vein (P < 0.001). In the brachial artery, but not in the posterior tibial artery, flow increased markedly at the highest levels of distending pressure (P < 0.001). At the highest intravascular pressures, the rate of change in tissue impedance was greater in the forearm than the lower leg (P < 0.01). At any given level of markedly increased pressure, pain was rated higher in the arm than in the leg (P < 0.001). Conclusion: It seems that the wall stiffness of arteries, pre-capillary resistance vessels and veins adapts to meet the long-term demands imposed by the hydrostatic pressure acting locally on the vessel walls.

  • 11.
    Eiken, Ola
    et al.
    Swedish Defence Research Agency.
    Kölegård, Roger
    Swedish Defence Research Agency.
    Relationship between arm pain and distension of arteries and veins caused by elevation of transmural pressure in local vascular segments2001In: Aviation, Space and Environmental Medicine, ISSN 0095-6562, E-ISSN 1943-4448, Vol. 72, no 5, p. 427-431Article in journal (Refereed)
    Abstract [en]

    BACKGROUND: Exposure to high +Gz forces may induce arm pain, which has been hypothesized to be caused by pressure-induced overdistension of local blood vessels. The purpose of the present investigation was to study the pressure-distension relation of veins and arteries in the human arm and the relation between arm pain and distension of local vessels.

    METHODS: Increased distending pressures (DP) in the vasculature of the arm were accomplished by placing the subject (n = 8) in a pressure chamber with one arm positioned through a port in the chamber door, and increasing chamber pressure to +180 mm Hg in a stepwise manner. Diameters in the brachial artery and in the brachial, radial and cephalic veins were measured by ultrasonography. Changes in forearm volume were estimated from measurement of tissue impedance. Perceived pain was rated using a 10-point scale.

    RESULTS: Arm pain increased with pressure to a maximum rating of 8.5 (= median; range: 4-10). Increasing DP from 30 to 180 mm Hg resulted in a steady increase (p < 0.05) in venous diameter which varied from 12 +/- 8% (mean +/- SD) in the brachial vein to 23 +/- 14% in the radial vein. Inthe brachial vein diameter increases were most pronounced at the sites of the venous valves. Arterial diameter was unchanged up to a DP of about 200 mm Hg (calculated as diastolic arterial pressure + applied chamber pressure), but then increased by 32 +/- 9% (p < 0.001). Forearm impedance dropped with increasing pressure (delta = 23 +/- 5%; p < 0.01); the rate of change was non-linear with a faster change at the highest DP which may indicate pressure distension of precapillary resistance vessels.

    CONCLUSIONS: Elevation of pressure in arm vessels to levels that may occur in pilots flying high-performance aircraft results in distension not only of veins but also of arteries and probably of smaller precapillary vessels. Therefore, and because these changes coincide with the development of severe arm pain, local overdistension of blood vessels remains a plausible cause of G-induced arm pain.

  • 12.
    Eiken, Ola
    et al.
    KTH, School of Technology and Health (STH), Environmental Physiology.
    Kölegård, Roger
    KTH, School of Technology and Health (STH), Environmental Physiology.
    Repeated exposures to moderately increased intravascular pressure increases stiffness in human arteries and arterioles2011In: Journal of Hypertension, ISSN 0263-6352, E-ISSN 1473-5598, Vol. 29, no 10, p. 1963-1971Article in journal (Refereed)
    Abstract [en]

    The aim was to investigate whether repeated exposures to moderate pressure elevations in the blood vessels of the arms (pressure training; PT) affect pressure distension in arteries/arterioles of healthy subjects (n=11). PT and vascular pressure-distension determinations were conducted with the subject seated in a pressure chamber with one arm slipped through a hole in the chamber door. Increased intravascular pressure was accomplished by increasing chamber pressure. Before PT, one arm was investigated (control arm) during stepwise increases in chamber pressure to 180 mmHg. Artery diameter and flow were measured in the brachial artery using ultrasonography/Doppler techniques. Thereafter, the contralateral arm underwent a PT regimen consisting of three 40 min sessions/ week during 5 weeks. Chamber pressure was increased during PT from 65 mmHg during the first week to 105 mmHg during the last week. After PT, pressure-distension relationships were examined in both the trained arm and the control arm. Prior to and following PT, endothelium-dependent and endothelium-independent dilatations of the brachial artery were studied. PT reduced (p<0.01) arterial pressure distension by 46 ± 18%. Likewise, the pressure-induced increase in arterial flow was less pronounced after (350 ± 249%) compared with before (685 ± 216 %) PT. The PT-induced reductions in arterial/arteriolar pressure distension were reversed 5 weeks post-PT. Neither endothelium-dependent nor endothelium-independent arterial dilatation were affected by PT. It thus appears that the in vivo wall stiffness in arteries and arterioles increases markedly in response to intermittent, moderate increments of transmural pressure during 5 weeks. The increases in arterial/arteriolar stiffness are reversible and do not reflect a reduced capacity to dilate the vessels. The findings are compatible with the notion that local load serves as “ a prime mover” in the development of vascular changes in hypertension.

  • 13.
    Eiken, Ola
    et al.
    Swedish Defence Research Agency.
    Kölegård, Roger
    Swedish Defence Research Agency.
    Lindborg, B.
    Swedish Defence Research Agency.
    Mekjavic, I. B.
    Linder, J.
    The effect of straining maneuvers on G-protection during assisted pressure breathing2003In: Aviation, Space and Environmental Medicine, ISSN 0095-6562, E-ISSN 1943-4448, Vol. 74, no 8, p. 822-826Article in journal (Refereed)
    Abstract [en]

    INTRODUCTION: Pilots flying high-performance aircraft increase their acceleration tolerance by using straining maneuvers and anti-G suits. Recently, assisted positive pressure breathing has been added in some aircraft systems. This study assessed the effect of anti-G straining maneuvers on the G-protective properties of one such system, the AGE-39 anti-G ensemble used in the Swedish JAS 39 Gripen aircraft.

    METHODS: Ten subjects were studied in a centrifuge using each of the following: 1) the AGE-39 in combination with anti-G straining maneuvers (AGSM) throughout each high-G exposure (full maneuver; FM); 2) the AGE-39 in combination with AGSM only during the initial part of each high-G exposure (reduced maneuver; RM). G-tolerance was established during exposures to rapid onset rate (ROR) G profiles with plateau levels ranging from 6.5 to 9.0 G.

    RESULTS: Mean G-tolerance was > or = 8.8 G (range: 8.5 to > or = 9.0 G) in the RM condition and > or = 9.0 G in all subjects in the FM condition. Mean arterial pressure was 30-50 mm Hg higher (p < 0.001) in the FM than in the RM condition at any given ROR G-load.

    CONCLUSIONS: AGE-39 in combination with a brief period of straining provide efficient G-protection as illustrated by the finding that all subjects could tolerate 8.5 G while performing AGSM during the initial part of the high-G exposures. However, at 9.0 G, 40% of the subjects had to perform AGSM throughout the duration of the G-exposure. That arterial pressure was only 30-50 mm Hg higher in the FM than RM condition suggests that in the presence of straining maneuvers, pressure breathing makes only a minute contribution to the arterial-pressure response.

  • 14.
    Eiken, Ola
    et al.
    Swedish Defence Research Agency.
    Kölegård, Roger
    Swedish Defence Research Agency.
    Lindborg, Bertil
    Aldman, M.
    Karlmar, K. E.
    Linder, J.
    A new hydrostatic anti-G suit vs. a pneumatic anti-G system: preliminary comparison.2002In: Aviation, Space and Environmental Medicine, ISSN 0095-6562, E-ISSN 1943-4448, Vol. 73, no 7, p. 703-708Article in journal (Refereed)
    Abstract [en]

    HYPOTHESIS: A newly developed hydrostatic anti-G suit is now commercially available. The suit is said to offer a high level of protection against +Gz acceleration. However, past experience shows that it is difficult to produce a hydrostatic suit with effective high-G protection. Careful testing is, therefore, needed to verify its efficacy.

    METHODS: The G-protective properties of the hydrostatic anti-G suit (Libelle; L) were compared with those of a pneumatic anti-G ensemble (AGE-39) used in the Swedish JAS 39 Cripen aircraft. Three pilots were studied during vertical (+Gz) acceleration in a centrifuge using the following: 1) the L-suit with varied straining maneuvers; 2) the AGE-39 in combination with full anti-G straining maneuvers (AGSM) throughout each high-G exposure (full maneuver; FM); and 3) the AGE-39 in combination with AGSM during the initial part of each high-G exposure (reduced maneuver; RM). G-intensity tolerance was established during exposures to rapid onset rate (ROR) profiles with G-plateau levels ranging from +6.0 to +9.0 Gz. G-endurance was studied during simulated aerial combat maneuvers (SACM) consisting of 10 cycles of 5.5 to 7.5 G.

    RESULTS: All three pilots tolerated 9.0 G with the pneumatic system both in the RM and FM conditions; their tolerances averaged 6.3 G (range 6.0 to 7.0 G) for the L suit. Thus, during the ROR exposures only the 6.0 G profile was completed by all subjects in all three conditions. At this G-load both muscle straining (as indicated by electromyographic activity in thigh and abdomen) and heart rate were higher in the L than in the RM condition. Mean arterial pressure at eye level was higher in the FM than in the L and RM conditions. Only one subject was able to complete the SACM profile in the L condition. In the RM condition all subjects completed the SACM profile and in the FM condition two subjects completed the SACM.

    CONCLUSIONS: Whether the AGE-39 was used in combination with maximal AGSM throughout the duration of each high-G exposure or with AGSM only during the initial part of the high-G exposure, G-intensity tolerance was 9.0 G. While wearing the L-suit, G-tolerance was 6.3 G. Thus, under the conditions tested, the G-protection afforded by the L-suit is not adequate for use in a 9-G aircraft.

  • 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.
    Eiken, Ola
    et al.
    KTH, School of Technology and Health (STH), Environmental Physiology (Closed 20130701).
    Mekjavic, I.
    Sundblad, Patrik
    KTH, School of Technology and Health (STH), Environmental Physiology (Closed 20130701).
    Kölegård, Roger
    KTH, School of Technology and Health (STH), Environmental Physiology (Closed 20130701).
    G tolerance vis-à-vis pressure-distension and pressure-flow relationships of leg arteries2012In: European Journal of Applied Physiology, ISSN 1439-6319, E-ISSN 1439-6327, Vol. 112, no 10, p. 3619-3627Article in journal (Refereed)
    Abstract [en]

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

  • 18.
    Eiken, Ola
    et al.
    KTH, School of Technology and Health (STH), Environmental Physiology.
    Mekjavic, IB
    Kounalakis, S
    Kölegård, Roger
    KTH, School of Technology and Health (STH), Environmental Physiology.
    Stiffness in leg arteries/arterioles is reduced by prolonged bedrest.2011Conference paper (Refereed)
  • 19.
    Eiken, Ola
    et al.
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Mekjavic, IB
    Kounalakis, SN
    Kölegård, Roger
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Pressure distension in leg vessels as influenced by prolonged bed rest and a pressure habituation regimen2016In: Journal of applied physiology, ISSN 8750-7587, E-ISSN 1522-1601, Vol. 120, no 12, p. 1458-1465Article in journal (Refereed)
    Abstract [en]

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

  • 20.
    Eiken, Ola
    et al.
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology. KTH, School of Technology and Health (STH), Centres, Swedish Aerospace Physiology Centre, SAPC.
    Mekjavic, Igor B.
    Kölegård, Roger
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology. KTH, School of Technology and Health (STH), Centres, Swedish Aerospace Physiology Centre, SAPC.
    Blood pressure regulation V: in vivo mechanical properties of precapillary vessels as affected by long-term pressure loading and unloading2014In: European Journal of Applied Physiology, ISSN 1439-6319, E-ISSN 1439-6327, Vol. 114, no 3, p. 499-509Article, review/survey (Refereed)
    Abstract [en]

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

  • 21.
    Eiken, Ola
    et al.
    Swedish Defence Research Agency.
    Tipton, Michael J.
    Kölegard, Roger
    Swedish Defence Research Agency.
    Lindborg, Bertil
    Swedish Defence Research Agency.
    Mekjavic, Igor B.
    Motion sickness decreases arterial pressure and therefore acceleration tolerance2005In: Aviation, Space and Environmental Medicine, ISSN 0095-6562, E-ISSN 1943-4448, Vol. 76, no 6, p. 541-546Article in journal (Refereed)
    Abstract [en]

    BACKGROUND: Motion sickness is a common aeromedical problem that may occur in pilots exposed to increased gravitoinertial load in the head-to-foot direction (+Gz). Since motion sickness may affect autonomic nervous functions including cardiovascular control, it was hypothesized that it might interfere with cardiovascular responses to high +Gz, thereby decreasing G tolerance.

    METHODS: G tolerance and cardiovascular responses to increased G load were studied in nine subjects in a centrifuge environment under two conditions. In the motion sickness condition, the subject was exposed to a motion sickness provocation (MSP) comprising repeated rapid changes in G load in combination with a regimen of head movements. In the control condition the subject was exposed to similar cumulative G-time stress, but without the MSP. Mean arterial pressure (MAP) was measured. An index of peripheral vascular resistance was achieved by measuring the difference in skin temperature between the forearm and fingertip (deltaT(forearm-fingertip)).

    RESULTS: MSP decreased gradual-onset rate G tolerance from 5.1 +/- 1.0 G (mean +/- SD) to 4.6 +/- 0.9 G. There was no change in gradual-onset rate G tolerance in the control condition. Rapid-onset rate G tolerance was lower in the motion sickness (2.9 +/- 0.5 G) than in the control (3.4 +/- 0.3 G) condition. MSP reduced MAP by 11 mmHg and deltaT(forearm-fingertip) by 4.2 +/- 4.1 degrees C. In the control condition MAP and deltaT(forearm-fingertip) were unaffected.

    CONCLUSIONS: Motion sickness may reduce the arterial pressure response to the extent that the capacity of an individual to withstand increased G loads in the head-to-foot direction is significantly diminished.

  • 22.
    Grönkvist, Mikael
    et al.
    Swedish Defence Research Agency.
    Bergsten, Eddie
    Swedish Defence Research Agency.
    Kölegård, Roger
    Swedish Defence Research Agency.
    Linder, Jan
    Eiken, Ola
    Swedish Defence Research Agency.
    G tolerance and pulmonary effects of removing chest counterpressure during pressure breathing2005In: Aviation, Space and Environmental Medicine, ISSN 0095-6562, E-ISSN 1943-4448, Vol. 76, no 9, p. 833-40Article in journal (Refereed)
    Abstract [en]

    BACKGROUND: In agile fighter aircraft positive pressure breathing is commonly used as part of the anti-G ensemble. To optimize G protection and prevent over-distention of the lungs, increased airway pressure is balanced by applying a counterpressure to the chest. The aim was to investigate the efficacy of chest counterpressure.

    METHODS: Three series of experiments were performed using the anti-G ensemble of the 39 Gripen aircraft (AGE-39) and exposing the subjects to 20-s G time profiles; in the first (n = 12) up to +8.0 Gz, in the second (n = 9) up to + 9.0 Gz, and also to simulated aerial combat maneuvers (SACM). Central and peripheral vision, arterial and airway pressures, pressure in the lower portion of the esophagus, and chest wall distension were measured. In the third series, six subjects were exposed to up to +7.0 Gz and esophageal pressure was measured in the upper thorax. In all series, two conditions were compared: with and without pressurized chest bladder.

    RESULTS: During the 20-s profiles arterial and esophageal pressures, chest wall distension, and visual impairment were similar with and without pressurized chest bladder. Upper esophageal pressure was slightly higher by 10-24% with than without chest bladder (p = 0.03). During SACM, time to exhaustion and the level of perceived exertion were similar with and without pressurized chest bladder.

    SUMMARY: The results suggest that the chest counterpressure can be removed from the AGE-39 without diminishing G tolerance or G endurance or significantly increasing the risk of lung parenchyma disruption.

  • 23. 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.

  • 24. Kacin, Alan
    et al.
    Mekjavic, Igor B.
    Rodman, Samuel
    Kolegard, Roger
    Swedish Defence Research Agency.
    Eiken, Ola
    Swedish Defence Research Agency.
    Influence of active recovery following prolonged bed rest on static exercise pressor response2002In: Journal of gravitational physiology : a journal of the International Society for Gravitational Physiology, ISSN 1077-9248, Vol. 501, p. 197-198Article in journal (Refereed)
    Abstract [en]

    The present study investigated the effect of active recovery, following 35 days of horizontal bed rest, on the magnitude and time course of the pressor and heart rate responses to sustained 90 minute submaximal isometric contraction of unilateral knee extensor muscles. Ten healthy male subjects were tested immediately post bed rest (Post BR) and again after 4 weeks of active recovery (Recovery). In both trials subjects sustained an absolute force equal to 30% of Post BR maximal voluntary contraction (MVC). Beat-to-beat heart rate (HR) and mean arterial blood pressure (MAP) were monitored continuously during sustained contraction using the volume-clamp technique. Despite a 24% increase in MVC, there were no significant differences in the magnitudes of HR and MAP responses between Post BR and Recovery trials, suggesting a bed rest-induced attenuation of the static exercise pressor response.

  • 25.
    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.

  • 26.
    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.

  • 27.
    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.
    Hand temperature responses to local cooling after a 10-day confinement to normobaric hypoxia with and without exercise2015In: Scandinavian Journal of Medicine and Science in Sports, ISSN 0905-7188, E-ISSN 1600-0838, Vol. 25, no 5, p. 650-660Article in journal (Refereed)
    Abstract [en]

    The study examined the effects of a 10-day normobaric hypoxic confinement (FiO2: 0.14), with (HT; n = 8) or without (HA; n = 6) exercise, on the hand-temperature responses during and after local cold stress. Before and after the confinement, subjects immersed their right hand for 30 min in 8°C water (CWI), followed by a 15-min spontaneous rewarming (RW), while breathing either room air (AIR), or a hypoxic gas mixture (HYPO). The hand-temperature responses were monitored with thermocouples and infrared-thermography. The confinement did not influence the hand-temperature responses of the HA group during the AIR and HYPO CWI and the HYPO RW phases; but it impaired the AIR RW response (-1.3°C; P = 0.05). After the confinement, the hand-temperature responses were unaltered in the HT group throughout the AIR trial. However, the average hand-temperature was increased during the HYPO CWI (+0.5°C; P ≤ 0.05) and RW (+2.4°C; P ≤ 0.001) phases. Accordingly, present findings suggest that prolonged exposure to normobaric hypoxia per se does not alter the hand-temperature responses to local cooling; yet, it impairs the normoxic rewarming response. Conversely, the combined stimuli of continuous hypoxia and exercise enhance the finger cold-induced vasodilatation and hand-rewarming responses, specifically, under hypoxic conditions.

  • 28.
    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.

  • 29.
    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.

  • 30.
    Keramidas, Michail
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Environmental Physiology. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Swedish Aerospace Physiology Centre, SAPC.
    Kölegård, Roger
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Environmental Physiology. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Swedish Aerospace Physiology Centre, SAPC.
    Eiken, Ola
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Environmental Physiology. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Swedish Aerospace Physiology Centre, SAPC.
    In Shackleton’s trails: central and local thermoadaptive modifications to cold and hypoxia after a man-hauling expedition on the Antarctic Plateau2018In: Journal of Thermal Biology, ISSN 0306-4565, E-ISSN 1879-0992, Vol. 73, p. 80-90Article in journal (Refereed)
    Abstract [en]

    Cold and hypoxia constitute the main environmental stressors encountered on the Antarctic Plateau. Hence, we examined whether central and/or peripheral acclimatisation to the combined stressors of cold and hypoxia would be developed in four men following an 11-day man-hauling expedition on this polar region. Before and after the journey, participants performed a static whole-body immersion in 21 degrees C water, during which they were breathing a hypoxic gas (partial pressure of inspired 02: 97 mmHg). To evaluate their local responses to cold, participants also immersed the hand into 8 degrees C water for 30 min, while they were whole-body immersed and mildly hypothermic [i.e. 0.5 degrees C fall in rectal temperature (T-rec) from individual pre-immersion values]. T-rec, and aldn temperature (T-ak), skin blood flux, and oxygen uptake (reflecting shivering thermogenesis) were monitored throughout. The polar expedition accelerated by similar to 14 min the drop in Trr, [final mean (95% confidence interval) changes in T-rec: Before = -0.94 (0.15) degrees C, After: 1.17 (0.23) degrees C]. The shivering onset threshold [Before: 19 (22) min, After: 25 (19) min] and gain [Before: 4.19 (3.95) mL min(-1) kg, After: 1.70 (1.21) mi. min(-1) kg(-1)] were suppressed by the expedition. TA did not differ between trials. The development of a greater post expedition hypothermic state did not compromise finger circulation during the hand-cooling phase. Present findings indicate therefore that a hypothermic pattern of cold acclimatisation, as investigated in hypoxia, was developed following a short-term expedition on the South Polar Plateau; an adaptive response that is characterised mainly by suppressed shivering thermogenesis, and partly by blunted cutaneous vasoconstriction.

  • 31. Kounalakis, S.N.
    et al.
    Keramidas, Michail E.
    Jozef Stefan Institute, SLOVENIA.
    Kölegård, Roger
    Royal Institute of Technology, SLOVENIA.
    Eiken, Ola
    Royal Institute of Technology, SLOVENIA.
    Mekjavic, I.B.
    Effect of 10 days hypoxic confinement on respiratory and leg muscle oxygenation during maximal exercise2012Conference paper (Refereed)
  • 32.
    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.

  • 33.
    Kölegård, Roger
    KTH, School of Technology and Health (STH), Environmental Physiology.
    Distensibility in Arteries, Arterioles and Veins in Humans: Adaptation to Intermittent or Prolonged Change in Regional Intravascular Pressure2010Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The present series of in vivo experiments in healthy subjects, were performed to investigate wall stiffness in peripheral vessels and how this modality adapts to iterative increments or sustained reductions in local intravascular pressures. Vascular stiffness was measured as changes in arterial and venous diameters, and in arterial flow, during graded increments in distending pressures in the vasculature of an arm or a lower leg. In addition, effects of intravascular pressure elevation on flow characteristics in veins, and on limb pain were elucidated. Arteries and veins were stiffer (i.e. pressure distension was less) in the lower leg than in the arm. The pressure-induced increase in arterial flow was substantially greater in the arm than in the lower leg, indicating a greater stiffness in the arterioles of the lower leg. Prolonged reduction of intravascular pressures in the lower body, induced by 5 wks of sustained horizontal bedrest (BR), decreased stiffness in the leg vasculature. BR increased pressure distension in the tibial artery threefold and in the tibial vein by 86 %. The pressure-induced increase in tibial artery flow was greater post bedrest, indicating reduced stiffness in the arterioles of the lower leg. Intermittent increases of intravascular pressures in one arm (pressure training; PT) during a 5-wk period decreased vascular stiffness. Pressure distension and pressure-induced flow in the brachial artery were reduced by about 50 % by PT. PT reduced pressure distension in arm veins by 30 to 50 %. High intravascular pressures changed venous flow to arterial-like pulsatile patterns, reflecting propagation of pulse waves from the arteries to the veins either via the capillary network or through arteriovenous anastomoses. High vascular pressures induced pain, which was aggravated by BR and attenuated by PT; the results suggest that the pain was predominantly caused by vascular overdistension. In conclusion, vascular wall stiffness constitutes a plastic modality that adapts to meet demands imposed by a change in the prevailing local intravascular pressure. That increased intravascular pressure leads to increased arteriolar wall stiffness supports the notion that local pressure load may serve as a “prime mover” in the development of vascular changes in hypertension.

  • 34.
    Kölegård, Roger
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Environmental Physiology.
    Da Silva, C.
    Siebenmann, Christoph
    KTH.
    Keramidas, Michail E.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Swedish Aerospace Physiology Centre, SAPC.
    Eiken, Ola
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Environmental Physiology.
    Cardiac performance is influenced by rotational changes of position in the transversal plane, both in the horizontal and in the 60̊ head-up postures2018In: Clinical Physiology and Functional Imaging, ISSN 1475-0961, E-ISSN 1475-097X, Vol. 38, no 6, p. 1021-1028Article in journal (Refereed)
    Abstract [en]

    Background: Echocardiography is usually performed with the subject/patient lying in the left lateral position (LLP), because the acoustic window is better in this than in the supine position (SP). The aim was to investigate cardiac responses to rotational changes of position in the transversal plane, from SP to LLP while horizontal, and from leaning on the back (HUT-LB) to leaning on the left side (HUT-LL) while tilted 60° head-up from the horizontal. Methods: Healthy men (n = 12) underwent 10-min HUT provocations. Cardiac variables were measured using two-dimensional echocardiography, Doppler, tissue Doppler imaging and arterial pressures using a volume-clamp method. Results: In horizontal posture, cardiac volumes were smaller in SP than in LLP: end-diastolic volume (EDV) by 14%, end-systolic volume (ESV) by 13%, stroke volume (SV) by 14%, and cardiac output (CO) by 16% (P<0·03). In addition, the mitral annular plane systolic excursion (MAPSE) was 11% smaller (P = 0·001) and the left ventricle isovolumic relaxation time (IVRT) 27% longer in SP than in LLP. The ejection fraction, heart rate, arterial pressure and pulmonary ventilation were similar in SP and LLP. During HUT, EDV, SV, CO and MAPSE were smaller, and IVRT was longer, in HUT-LB than in HUT-LL, by −19%, −20%, −17%, −18% and +35%, respectively (P<0·04). Conclusions: Cardiac performance is enhanced in LLP versus SP and in HUT-LL versus HUT-LB, which can be attributed to improved venous return, conceivably, wholly or in part, due to increased hydrostatic pressure gradients between the caval veins and the heart in the LLP and HUT-LL positions.

  • 35.
    Kölegård, Roger
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Environmental Physiology.
    Da Silva, Cristina
    Siebenmann, Christoph
    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.
    Eiken, Ola
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Environmental Physiology.
    Cardiac performance is influenced by rotational changes of position in the transversal plane, both in the horizontal and 60° head-up posture2018In: Clinical Physiology and Functional Imaging, ISSN 1475-0961, E-ISSN 1475-097XArticle in journal (Refereed)
  • 36.
    Kölegård, Roger
    et al.
    Karolinska Inst, Swedish Def Res Agcy.
    Eiken, Ola
    Karolinska Inst, Swedish Def Res Agcy.
    Antegrade pulsatile arterial-like flow in human limb veins at increased intravascular pressure2009In: Clinical Physiology and Functional Imaging, ISSN 1475-0961, E-ISSN 1475-097X, Vol. 29, no 3, p. 209-215Article in journal (Refereed)
    Abstract [en]

    The purpose was to study the effects of moderately to markedly increased local intravascular pressures on the flow characteristics in human limb veins. The subject was either seated inside a pressure chamber with one arm slipped through a hole in the chamber door (n = 7) or positioned supine with a lower leg extended to the outside (n = 15). By increasing chamber pressure, transmural pressure in the vessels of the test limb was increased up to +150 mmHg for the arm and +240 mmHg for the leg. Venous flow profiles and arterial flow and vessel diameters were measured with ultrasonographic/Doppler techniques. The arm vessels were studied before and during blocking of the blood flow (BBF) through the hand. Antegrade, pulsatile, arterial-like flow were observed at high distending pressures in the brachial and radial veins in all subjects and in similar to 50% of the subjects also in the cephalic vein and posterior tibial veins. In five of seven subjects, blood flow in the brachial vein remained pulsatile even during BBF. That pulsatile flow was observed in all veins may suggest that moderately to markedly elevated intravascular pressures induce propagation of pulse waves from the arteries via the capillaries to the veins, and/or induce considerable arteriovenous shunting, by forcing open arteriovenous anastomoses.

  • 37.
    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)
  • 38.
    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.

  • 39.
    Kölegård, Roger
    et al.
    Karolinska Inst, Swedish Def Res Agcy.
    Mekjavic, Igor B.
    Karolinska Inst, Swedish Def Res Agcy.
    Eiken, Ola
    Karolinska Inst, Swedish Def Res Agcy.
    Increased distensibility in dependent veins following prolonged bedrest2009In: European Journal of Applied Physiology, ISSN 1439-6319, E-ISSN 1439-6327, Vol. 106, no 4, p. 547-554Article in journal (Refereed)
    Abstract [en]

    Displacement of blood to the lower portion of the body that follows a postural transition from recumbent to erect is augmented by a prolonged period of recumbency (bedrest). Information is scarce as to what extent this augmented blood-volume shift to dependent veins is attributable to increased distensibility of the veins. Accordingly, we studied the effect of 5 weeks of horizontal bedrest on the pressure-distension relationship in limb veins. Elevation of venous distending pressure was induced by exposure of the body except the tested limb to supra-atmospheric pressure with the subject seated in a pressure chamber with one arm, or supine with a lower leg, protruding through a hole in the chamber door. Diameter changes in response to an increase of intravenous pressure (distensibility) from 60 to about 140 mmHg were measured in the brachial and posterior tibial veins using ultrasonographic techniques. Prior to bedrest, the distensibility was substantially less in the tibial than in the brachial vein. Bedrest increased (P < 0.01) pressure distension in the tibial vein by 86% from 7 +/- A 3% before to 13 +/- A 3% after bedrest. In the brachial vein, bedrest increased (P < 0.05) pressure distension by 36% from 14 +/- A 5% before to 19 +/- A 5% after bedrest. Thus, removal of the gravity-dependent pressure components that act along the blood vessels in erect posture increases the distensibility of dependent veins.

  • 40.
    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)
  • 41. Lund, F.
    et al.
    Jogestrand, T.
    Kölegård, Roger
    Huddinge Hospital.
    Computerized analysis of video fluorescein imaging (VFI) of the skin2000In: Clinical Physiology, ISSN 0144-5979, E-ISSN 1365-2281, Vol. 20, no 5, p. 374-379Article in journal (Refereed)
    Abstract [en]

    Video fluorescein imaging (VFI) is a new technique to continuously follow the development of fluorescence in the skin, i.e. blood inflow and perfusion, after intravenous injection of sodium fluorescein. The method is supplementary to other microcirculatory techniques for evaluation of peripheral arterial occlusive disease, particularly in critical ischaemia. In the present article we describe a totally computerized digital imaging processing system for evaluation and present results from a comparison between the evaluations of the appearance and development of the fluorescence in the sole of the foot using the computerized and the previously used manual techniques. With the computerized system the images are stored and correlated with the start of the injection. Regions of interest are then marked and a mean value of fluorescence intensity is calculated for each image. Using this computerized system the time required for evaluation has been shortened to about 10 min. The results of the comparison between the manual and computerized evaluations of appearance times showed that a significant correlation existed in all examined parts of the feet between the two techniques. The methods gave approximately the same results in regions with fluorescence appearance times between 20 and 50 s. With longer appearance times than approximately 50 s a systematic difference between the two techniques seemed to exist. In this interval shorter appearance times were measured with the computerized technique than with the manual technique. However, the clinical information with regard to prognosis would be relatively unchanged when the new computerized assessment technique and a new cut-off level for the appearance time are used. Also, regarding the development of fluorescence after the appearance time, expressed by the slope, a significant correlation was found between the manual and the computerized evaluation.

  • 42. MacDonnell, A.
    et al.
    Pavlinič, D.
    Ciuha, U.
    Kölegård, Roger
    KTH, School of Technology and Health (STH), Environmental Physiology.
    Eiken, Ola
    KTH, School of Technology and Health (STH), Environmental Physiology.
    Mekjavic, I.
    The correlation between the cold-induced vasodilatation response and toe skin temperature during winter hikes in the alps2011Conference paper (Refereed)
  • 43. Mekjavic, I. B.
    et al.
    McDonnell, A. C.
    Keramidas, Michail E.
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Kolegard, Roger
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Lind, Britta
    KTH, School of Technology and Health (STH), Medical Engineering, Medical Imaging.
    Eiken, Ola
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Lunar habitat simulation2013Conference paper (Other academic)
  • 44. Mekjavic, I.B.
    et al.
    McDonnell, A.C.
    Keramidas, Michail E.
    Jozef Stefan Institute, SLOVENIA.
    Kölegard, Roger
    KTH, School of Technology and Health (STH), Environmental Physiology (Closed 20130701).
    Lind, Britta
    KTH, School of Technology and Health (STH), Medical Engineering.
    Eiken, Ola
    KTH, School of Technology and Health (STH), Environmental Physiology (Closed 20130701).
    Hypoxic bedrest: Implications for planetary habitats2012Conference paper (Refereed)
  • 45. Mekjavic, Igor B.
    et al.
    Amon, Mojca
    Kölegård, Roger
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Kounalakis, Stylianos N.
    Simpson, Liz
    Eiken, Ola
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Keramidas, Michail E.
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    MacDonald, IanA.
    The effect of normobaric hypoxic confinement on metabolism, gut hormones and body composition2016In: Frontiers in Physiology, ISSN 1664-042X, E-ISSN 1664-042X, Vol. 7, no 202Article in journal (Refereed)
  • 46.
    Nobel, Gerard
    et al.
    KTH, School of Technology and Health (STH), Environmental Physiology.
    Eiken, Ola
    KTH, School of Technology and Health (STH), Environmental Physiology.
    Tribukait, Arne
    KTH, School of Technology and Health (STH), Environmental Physiology.
    Kölegård, Roger
    KTH, School of Technology and Health (STH), Environmental Physiology.
    Mekjavic, Igor B.
    Motion sickness increases the risk of accidental hypothermia2006In: European Journal of Applied Physiology, ISSN 1439-6319, E-ISSN 1439-6327, Vol. 98, no 1, p. 48-55Article in journal (Refereed)
    Abstract [en]

    Motion sickness (MS) has been found to increase body-core cooling during immersion in 28 degrees C degrees C water, an effect ascribed to attenuation of the cold- induced peripheral vasoconstriction (Mekjavic et al. in J Physiol 535(2):619-623, 2001). The present study tested the hypothesis that a more profound cold stimulus would override the MS effect on peripheral vasoconstriction and hence on the core cooling rate. Eleven healthy subjects underwent two separate head-out immersions in 15 degrees C water. In the control trial (CN), subjects were immersed after baseline measurements. In the MS-trial, subjects were rendered motion sick prior to immersion, by using a rotating chair in combination with a regimen of standardized head movements. During immersion in the MS-trial, subjects were exposed to an optokinetic stimulus (rotating drum). At 5-min intervals subjects rated their temperature perception, thermal comfort and MS discomfort. During immersion mean skin temperature, rectal temperature, the difference in temperature between the non-immersed right forearm and 3rd finger of the right hand (Delta T (ff)), oxygen uptake and heart rate were recorded. In the MS-trial, rectal temperature decreased substantially faster (33%, P < 0.01). Also, the Delta T (ff) response, an index of peripheral vasomotor tone, as well as the oxygen uptake, indicative of the shivering response, were significantly attenuated (P < 0.01 and P < 0.001, respectively) by MS. Thus, MS may predispose individuals to hypothermia by enhancing heat loss and attenuating heat production. This might have significant implications for survival in maritime accidents.

  • 47.
    Norrbrand, Lena
    et al.
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Kölegård, Roger
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Keramidas, Michail E.
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Eiken, Ola
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Mekjavic, Igor B.
    No association between hand and foot temperature responses during local cold stress and rewarming.2017In: European Journal of Applied Physiology, ISSN 1439-6319, E-ISSN 1439-6327, Vol. 117, no 6, p. 1141-1153Article in journal (Refereed)
    Abstract [en]

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

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

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

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

  • 48. Salvadego, Desy
    et al.
    Keramidas, Michail E.
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology. KTH, School of Technology and Health (STH), Centres, Swedish Aerospace Physiology Centre, SAPC.
    Domenis, Rossana
    Kölegård, Roger
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology. KTH, School of Technology and Health (STH), Centres, Swedish Aerospace Physiology Centre, SAPC.
    Mavelli, Irene
    Rittweger, Jorn
    Eiken, Ola
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology. KTH, School of Technology and Health (STH), Centres, Swedish Aerospace Physiology Centre, SAPC.
    Mekjavic, Igor B.
    Grassi, Bruno
    PlanHab: responses of skeletal muscle oxidative function to bed rest and hypoxia2015Conference paper (Refereed)
  • 49.
    Salvadego, Desy
    et al.
    Univ Udine, Dept Med, Piazzale M Kolbe 4, I-33100 Udine, Italy..
    Keramidas, Michail E.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Environmental Physiology. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Swedish Aerospace Physiology Centre, SAPC.
    Kölegård, Roger
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Environmental Physiology. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Swedish Aerospace Physiology Centre, SAPC.
    Brocca, Lorenza
    Univ Pavia, Dept Mol Med, Pavia, Italy..
    Lazzer, Stefano
    Univ Udine, Dept Med, Piazzale M Kolbe 4, I-33100 Udine, Italy..
    Mavelli, Irene
    Univ Udine, Dept Med, Piazzale M Kolbe 4, I-33100 Udine, Italy..
    Rittweger, Joern
    German Aerosp Ctr, Inst Aerosp Med, Cologne, Germany.;Univ Cologne, Fac Med, Dept Pediat & Adolescent Med, Cologne, Germany..
    Eiken, Ola
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Environmental Physiology. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Swedish Aerospace Physiology Centre, SAPC.
    Mekjavic, Igor B.
    Jozef Stefan Inst, Dept Automat Biocybernet & Robot, Ljubljana, Slovenia.;Simon Fraser Univ, Dept Biomed Physiol & Kinesiol, Burnaby, BC, Canada..
    Grassi, Bruno
    Univ Udine, Dept Med, Piazzale M Kolbe 4, I-33100 Udine, Italy.;CNR, Inst Bioimaging & Mol Physiol, Milan, Italy..
    PlanHab(*): hypoxia does not worsen the impairment of skeletal muscle oxidative function induced by bed rest alone2018In: Journal of Physiology, ISSN 0022-3751, E-ISSN 1469-7793, Vol. 596, no 15, p. 3341-3355Article in journal (Refereed)
    Abstract [en]

    Skeletal muscle oxidative function was evaluated in 11 healthy males (mean +/- SD age 27 +/- 5years) prior to (baseline data collection, BDC) and following a 21day horizontal bed rest (BR), carried out in normoxia (P-IO2=133 mmHg; N-BR) and hypoxia (P-IO2=90 mmHg; H-BR). H-BR was aimed at simulating reduced gravity habitats. The effects of a 21day hypoxic ambulatory confinement (P-IO2=90 mmHg; H-AMB) were also assessed. Pulmonary O-2 uptake (<(V) over dot>O-2), vastus lateralis fractional O-2 extraction (changes in deoxygenated haemoglobin+myoglobin concentration, Delta[deoxy(Hb+Mb)]; near-infrared spectroscopy) and femoral artery blood flow (ultrasound Doppler) were evaluated during incremental one-leg knee-extension exercise (reduced constraints to cardiovascular O-2 delivery) carried out to voluntary exhaustion in a normoxic environment. Mitochondrial respiration was evaluated ex vivo by high-resolution respirometry in permeabilized vastus lateralis fibres. <(V) over dot>(O2peak) decreased (P<0.05) after N-BR (0.98 +/- 0.13 L min(-1)) and H-BR (0.96 +/- 0.17 L min(-1)) vs. BDC (1.05 +/- 0.14 L min(-1)). In the presence of a decreased (by similar to 6-8%) thigh muscle volume, <(V) over dot>(O2peak) normalized per unit of muscle mass was not affected by both interventions. Delta[deoxy(Hb+Mb)](peak) decreased (P<0.05) after N-BR (65 +/- 13% of limb ischaemia) and H-BR (62 +/- 12%) vs. BDC (73 +/- 13%). H-AMB did not alter <(V) over dot>(O2peak) or Delta[deoxy(Hb+Mb)](peak). An overshoot of Delta[deoxy(Hb+Mb)] was evident during the first minute of unloaded exercise after N-BR and H-BR. Arterial blood flow to the lower limb during both unloaded and peak knee extension was not affected by any intervention. Maximal ADP-stimulated mitochondrial respiration decreased (P<0.05) after all interventions vs. control. In 21day N-BR, a significant impairment of oxidative metabolism occurred downstream of cardiovascular O-2 delivery, affecting both mitochondrial respiration and presumably the intramuscular matching between O-2 supply and utilization. Superposition of H on BR did not worsen the impairment induced by BR alone.

  • 50. Salvadego, Desy
    et al.
    Keramidas, Michail E.
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Kölegård, Roger
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Mavelli, Irene
    Eiken, Ola
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Mekjavic, Igor B.
    Grassi, Bruno
    Prolonged exposure to hypoxia and microgravity: effects on skeletal muscle oxidative metabolism2015Conference paper (Refereed)
12 1 - 50 of 54
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