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  • 1. Debevec, T.
    et al.
    Ganse, B.
    Mittag, U.
    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, I. B.
    Rittweger, J.
    Hypoxia aggravates inactivity-Related muscle wasting2018In: Frontiers in Physiology, ISSN 1664-042X, E-ISSN 1664-042X, Vol. 9, no May, article id 494Article in journal (Refereed)
    Abstract [en]

    Poor musculoskeletal state is commonly observed in numerous clinical populations such as chronic obstructive pulmonary disease (COPD) and heart failure patients. It, however, remains unresolved whether systemic hypoxemia, typically associated with such clinical conditions, directly contributes to muscle deterioration. We aimed to experimentally elucidate the effects of systemic environmental hypoxia upon inactivity-related muscle wasting. For this purpose, fourteen healthy, male participants underwent three 21-day long interventions in a randomized, cross-over designed manner: (i) bed rest in normoxia (NBR; PiO2 = 133.1 ± 0.3 mmHg), (ii) bed rest in normobaric hypoxia (HBR; PiO2 = 90.0 ± 0.4 mmHg) and ambulatory confinement in normobaric hypoxia (HAmb; PiO2 = 90.0 ± 0.4 mmHg). Peripheral quantitative computed tomography and vastus lateralis muscle biopsies were performed before and after the interventions to obtain thigh and calf muscle cross-sectional areas and muscle fiber phenotype changes, respectively. A significant reduction of thigh muscle size following NBR (-6.9%, SE 0.8%; P < 0.001) was further aggravated following HBR (-9.7%, SE 1.2%; P = 0.027). Bed rest-induced muscle wasting in the calf was, by contrast, not exacerbated by hypoxic conditions (P = 0.47). Reductions in both thigh (-2.7%, SE 1.1%, P = 0.017) and calf (-3.3%, SE 0.7%, P < 0.001) muscle size were noted following HAmb. A significant and comparable increase in type 2× fiber percentage of the vastus lateralis muscle was noted following both bed rest interventions (NBR = +3.1%, SE 2.6%, HBR = +3.9%, SE 2.7%, P < 0.05). Collectively, these data indicate that hypoxia can exacerbate inactivity-related muscle wasting in healthy active participants and moreover suggest that the combination of both, hypoxemia and lack of activity, as seen in COPD patients, might be particularly harmful for muscle tissue.

  • 2.
    Eiken, Ola
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Environmental Physiology.
    Omgivningsfysiologi vid KTH2018In: Bevingat, Vol. 2Article, review/survey (Other (popular science, discussion, etc.))
  • 3.
    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)
  • 4.
    Eiken, Ola
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Environmental Physiology.
    Tribukait, Arne
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Environmental Physiology.
    High G centrifuge training; Vestibular mechanisms for motion sickness during high-G training. CBH Report 2015-0197.2018Report (Other academic)
  • 5.
    Elia, Antonis
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Environmental Physiology. Research Institute for Sport, Physical Activity and Leisure, Leeds Beckett University, Leeds, United Kingdom.
    Barlow, Matthew J.
    Research Institute for Sport, Physical Activity and Leisure, Leeds Beckett University, Leeds, United Kingdom.
    Deighton, Kevin
    Research Institute for Sport, Physical Activity and Leisure, Leeds Beckett University, Leeds, United Kingdom.
    Wilson, Oliver J.
    Research Institute for Sport, Physical Activity and Leisure, Leeds Beckett University, Leeds, United Kingdom.
    O'Hara, John P.
    Research Institute for Sport, Physical Activity and Leisure, Leeds Beckett University, Leeds, United Kingdom.
    Erythropoietic responses to a series of repeated maximal dynamic and static apnoeas in elite and non-breath-hold divers2019In: European Journal of Applied Physiology, ISSN 1439-6319, E-ISSN 1439-6327, Vol. 119, no 11-12, p. 2557-2565Article in journal (Refereed)
    Abstract [en]

    PURPOSE: Serum erythropoietin (EPO) concentration is increased following static apnoea-induced hypoxia. However, the acute erythropoietic responses to a series of dynamic apnoeas in non-divers (ND) or elite breath-hold divers (EBHD) are unknown.

    METHODS: Participants were stratified into EBHD (n = 8), ND (n = 10) and control (n = 8) groups. On two separate occasions, EBHD and ND performed a series of five maximal dynamic apnoeas (DYN) or two sets of five maximal static apnoeas (STA). Control performed a static eupnoeic (STE) protocol to control against any effects of water immersion and diurnal variation on EPO. Peripheral oxygen saturation (SpO2) levels were monitored up to 30 s post each maximal effort. Blood samples were collected at 30, 90, and 180 min after each protocol for EPO, haemoglobin and haematocrit concentrations.

    RESULTS: No between group differences were observed at baseline (p > 0.05). For EBHD and ND, mean end-apnoea SpO2 was lower in DYN (EBHD, 62 ± 10%, p = 0.024; ND, 85 ± 6%; p = 0.020) than STA (EBHD, 76 ± 7%; ND, 96 ± 1%) and control (98 ± 1%) protocols. EBHD attained lower end-apnoeic SpO2 during DYN and STA than ND (p < 0.001). Serum EPO increased from baseline following the DYN protocol in EBHD only (EBHD, p < 0.001; ND, p = 0.622). EBHD EPO increased from baseline (6.85 ± 0.9mlU/mL) by 60% at 30 min (10.82 ± 2.5mlU/mL, p = 0.017) and 63% at 180 min (10.87 ± 2.1mlU/mL, p = 0.024). Serum EPO did not change after the STA (EBHD, p = 0.534; ND, p = 0.850) and STE (p = 0.056) protocols. There was a significant negative correlation (r = - 0.49, p = 0.003) between end-apnoeic SpO2 and peak post-apnoeic serum EPO concentrations.

    CONCLUSIONS: The novel findings demonstrate that circulating EPO is only increased after DYN in EBHD. This may relate to the greater hypoxemia achieved by EBHD during the DYN.

  • 6.
    Elia, Antonis
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Environmental Physiology. Research Institute for Sport, Physical Activity and Leisure, Leeds Beckett University, Leeds, United Kingdom.
    Wilson, Oliver J.
    Lees, Matthew
    Parker, Paul J.
    Barlow, Matthew J.
    Cocks, Matthew
    O'Hara, John P
    Skeletal muscle, haematological and splenic volume characteristics of elite breath-hold divers.2019In: European Journal of Applied Physiology, ISSN 1439-6319, E-ISSN 1439-6327, Vol. 119, no 11-12, p. 2499-2511Article in journal (Refereed)
    Abstract [en]

    PURPOSE: The aim of the study was to provide an evaluation of the oxygen transport, exchange and storage capacity of elite breath-hold divers (EBHD) compared with non-divers (ND).

    METHODS: Twenty-one healthy males' (11 EBHD; 10 ND) resting splenic volumes were assessed by ultrasound and venous blood drawn for full blood count analysis. Percutaneous skeletal muscle biopsies were obtained from the m. vastus lateralis to measure capillarisation, and fibre type-specific localisation and distribution of myoglobin and mitochondrial content using quantitative immunofluorescence microscopy.

    RESULTS: Splenic volume was not different between groups. Reticulocytes, red blood cells and haemoglobin concentrations were higher (+ 24%, p < 0.05; + 9%, p < 0.05; + 3%, p < 0.05; respectively) and mean cell volume was lower (- 6.5%, p < 0.05) in the EBHD compared with ND. Haematocrit was not different between groups. Capillary density was greater (+ 19%; p < 0.05) in the EBHD. The diffusion distance (R95) was lower in type I versus type II fibres for both groups (EBHD, p < 0.01; ND, p < 0.001), with a lower R95 for type I fibres in the EBHD versus ND (- 13%, p < 0.05). Myoglobin content was higher in type I than type II fibres in EBHD (+ 27%; p < 0.01) and higher in the type I fibres of EBHD than ND (+ 27%; p < 0.05). No fibre type differences in myoglobin content were observed in ND. Mitochondrial content was higher in type I than type II fibres in EBHD (+ 35%; p < 0.05), with no fibre type differences in ND or between groups.

    CONCLUSIONS: In conclusion, EBDH demonstrate enhanced oxygen storage in both blood and skeletal muscle and a more efficient oxygen exchange capacity between blood and skeletal muscle versus ND.

  • 7.
    Gennser, Mikael
    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.
    Blogg, S. L.
    SLB Consulting, Newbiggin On Lune, Cumbria, England..
    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..
    Indices of Increased Decompression Stress Following Long-Term Bed Rest2018In: Frontiers in Physiology, ISSN 1664-042X, E-ISSN 1664-042X, Vol. 9, article id 442Article in journal (Refereed)
    Abstract [en]

    Human extravehicular activity (EVA) is essential to space exploration and involves risk of decompression sickness (DCS). On Earth, the effect of microgravity on physiological systems is simulated in an experimental model where subjects are confined to a 6 degrees head-down bed rest (HDBR). This model was used to investigate various resting and exercise regimen on the formation of venous gas emboli (VGE), an indicator of decompression stress, post-hyperbaric exposure. Eight healthy male subjects participating in a bed rest regimen also took part in this study, which incorporated five different hyperbaric exposure (HE) interventions made before, during and after the HDBR. Interventions i-iv were all made with the subjects lying in 6 degrees HD position. They included (C1) resting control, (C2) knee-bend exercise immediately prior to HE, (T1) HE during the fifth week of the 35-day HDBR period, (C3) supine cycling exercise during the HE. In intervention (C4), subjects remained upright and ambulatory. The HE protocol followed the Royal Navy Table 11 with 100 min spent at 18 m (280 kPa), with decompression stops at 6 m for 5 min, and at 3 m for 15 min. Post-HE, regular precordial Doppler audio measurements were made to evaluate any VGE produced post-dive. VGE were graded according to the Kisman Masurel scale. The number of bubbles produced was low in comparison to previous studies using this profile [Kisman integrated severity score (KISS) ranging from 0-1], and may be because subjects were young, and lay supine during both the HE and the 2 h measurement period post-HE for interventions i-iv. However, the HE during the end of HDBR produced significantly higher maximum bubble grades and KISS score than the supine control conditions (p < 0.01). In contrast to the protective effect of pre-dive exercise on bubble production, a prolonged period of bed rest prior to a HE appears to promote the formation of post-decompression VGE. This is in contrast to the absence of DCS observed during EVA. Whether this is due to a difference between hypo- and hyperbaric decompression stress, or that the HDBR model is a not a good model for decompression sensitivity during microgravity conditions will have to be elucidated in future studies.

  • 8.
    Groselj, L. Dolenc
    et al.
    Univ Med Ctr, Inst Clin Neurophysiol, Ljubljana, Slovenia..
    Morrison, S.
    Univ Primorska, Fac Hlth, Izola, Slovenia..
    Mirnik, D.
    Univ Med Ctr, Inst Clin Neurophysiol, Ljubljana, Slovenia..
    Korsic, S.
    Univ Med Ctr, Inst Clin Neurophysiol, Ljubljana, Slovenia..
    Eiken, Ola
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Environmental Physiology.
    Mekjavic, I.
    Jozef Stefan Inst, Dept Automat Biocybernet & Robot, Ljubljana, Slovenia..
    BED REST AND HYPOXIC EXPOSURE AFFECT SLEEP ARCHITECTURE AND BREATHING STABILITY2017In: Sleep Medicine, ISSN 1389-9457, E-ISSN 1878-5506, Vol. 40, p. E80-E80Article in journal (Other academic)
  • 9. Groselj, L. Dolenc
    et al.
    Morrison, S.
    Univ Med Ctr, Inst Clin Neurophysiol, Ljubljana, Slovenia..
    Mirnik, D.
    Univ Med Ctr, Inst Clin Neurophysiol, Ljubljana, Slovenia..
    Korsic, S.
    Univ Med Ctr, Inst Clin Neurophysiol, Ljubljana, Slovenia..
    Eiken, Ola
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Environmental Physiology. Royal Inst Technol, Sch Technol & Hlth, Dept Environm Physiol, Stockholm, Sweden..
    Mekjavic, I.
    Jozef Stefan Inst, Dept Automat Biocybernet & Robot, Ljubljana, Slovenia..
    Prolonged bed rest and hypoxic exposure affect breathing stability and sleep macrostructure2016In: European Journal of Neurology, ISSN 1351-5101, E-ISSN 1468-1331, Vol. 23, p. 744-744Article in journal (Other academic)
  • 10.
    Grönkvist, Mikael
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Environmental Physiology.
    Gustafsson, Per
    Centralsjukhuset, Skövde.
    Eiken, Ola
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Environmental Physiology.
    Ventilationsfördelning i lungorna med och utan övertrycksandning vid ökad Gz-belastning med trycksatt anti-G-dräkt2018In: Proceedings from Swedish Aeronautical Medical Association, Annual Scientific Meeting, 2018 / [ed] Claes Bothin, 2018Conference paper (Refereed)
  • 11.
    Grönkvist, Mikael
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Environmental Physiology.
    LaPelusa, M.
    Univ Texas Rio Grande Valley, Sch Med, Edinburg, TX USA..
    Gennser, Mikael
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Environmental Physiology. Royal Inst Technol, Environm Physiol, Stockholm, Sweden..
    Machado-Moreira, Christiano Antonio
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Environmental Physiology.
    Postural and Daily Variations in the Single-Breath Diffusion Capacity of the Lungs for Carbon Monoxide2018In: American Journal of Respiratory and Critical Care Medicine, ISSN 1073-449X, E-ISSN 1535-4970, Vol. 197Article in journal (Other academic)
  • 12.
    Grönkvist, Mikael
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Environmental Physiology.
    Levin, Britta
    Eiken, Ola
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Environmental Physiology.
    G Tolerance During Open- vs. Closed-Loop G-Time Control.2018In: Aerospace Medicine and Human Performance, ISSN 2375-6314, E-ISSN 2375-6322, Vol. 89, no 9, p. 798-804Article in journal (Refereed)
    Abstract [en]

    BACKGROUND: +Gz tolerance is traditionally determined in centrifuges with open-loop G control, i.e., the centrifuge is under operator control (open loop), and thus the test subject is unable to influence the Gz load. In modern centrifuges, however, the subject is commonly able to continuously control the Gz load (closed loop). It is a widespread opinion among fighter pilots that +Gz tolerance is higher under closed- than open-loop G control. The aims were to investigate whether +Gz tolerance is higher in closed- than open-loop G control, and whether it is possible to use closed-loop G control during precise determination of +Gz tolerance.

    METHODS: Relaxed +Gz tolerance was determined in eight men during rapid Gz-onset rate (ROR) under three conditions: 1) OL-VFB, open loop with visual feedback; 2) OL-NFB, open loop with no visual feedback; and 3) CL, closed loop. Straining +Gz tolerance was determined in 10 men during ROR in OL and CL conditions.

    RESULTS: Relaxed +Gz tolerance did not differ between CL (3.66 Gz), OL-VFB (3.70 Gz) and OL-NFB (3.64 Gz). Straining +Gz tolerance was similar in the CL (8.5 Gz) and OL (8.6 Gz) conditions. In the CL condition, the Gz load varied substantially and was on average lower than in the OL conditions, at any stipulated G-time profile.

    DISCUSSION: There is no systematic difference in relaxed or straining +Gz tolerance as determined in closed- vs. open-loop G-controlled systems. During closed-loop control, precision and reproducibility are too low to recommend it for accurate determination of relaxed G tolerance.Grönkvist M, Levin B, Eiken O. G tolerance during open- vs. closed-loop G-time control. Aerosp Med Hum Perform. 2018; 89(9):798-804.

  • 13.
    Jönsson, Maria
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Environmental Physiology.
    Munkhammar, Tobias
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Environmental Physiology.
    Norrbrand, Lena
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Environmental Physiology.
    Berg, Hans E
    Karolinska Institutet.
    Foot centre of pressure and ground reaction force during quadriceps resistance exercises; a comparison between force plates and a pressure insole system.2019In: Journal of Biomechanics, ISSN 0021-9290, E-ISSN 1873-2380, Vol. 87, p. 206-210, article id S0021-9290(19)30182-4Article in journal (Refereed)
    Abstract [en]

    The study compared the centre of pressure measurements (COP) and vertical ground reaction forces (vGRF) from a pressure insole system to that from force plates (FP) during two flywheel quadriceps resistance exercises: leg press and squat. The comparison was performed using a motion capture system and simultaneous measurements of COP and vGRF from FP and insoles. At lower insole-vGRF (<250 N/insole) COP accuracy deteriorated and those data were excluded from further analysis. The insoles systematically displaced the COP slightly posteriorly and medially compared to the FP measurements. Pearson's coefficient of correlation (r) between insole- and FP-COP showed good agreement in both the anteroposterior (squat: r = 0.96, leg press: r = 0.97) and mediolateral direction (squat: r = 0.84, leg press: r = 0.90), whereas the root-mean-square errors (RMSE) were lower in the mediolateral (squat: 3.9 mm, leg press: 4.5 mm) than the anteroposterior (squat and leg press: 11.8 mm) direction. Vertical GRF was slightly overestimated by the insoles in leg press and RMSE were greater in leg press (8% of peak force) than in squat (6%). Overall, results were within the range of previous studies performed on gait. The strong agreement between insole and FP measurements indicates that insoles may replace FPs in field applications and biomechanical computations during resistance exercise, provided that the applied force is sufficient.

  • 14.
    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.

  • 15.
    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.
    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.
    Mekjavic, Igor B.
    Jozef Stefan Inst, Dept Automat Biocybernet & Robot, Ljubljana, Slovenia.;Simon Fraser Univ, Dept Biomed Physiol & Kinesiol, Burnaby, BC, Canada..
    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.
    Interactions of mild hypothermia and hypoxia on finger vasoreactivity to local cold stress2019In: American Journal of Physiology. Regulatory Integrative and Comparative Physiology, ISSN 0363-6119, E-ISSN 1522-1490, Vol. 317, no 3, p. R418-R431Article in journal (Refereed)
    Abstract [en]

    We examined the interactive effects of mild hypothermia and hypoxia on finger vasoreactivity to local cold stress. Eight male lowlanders performed, in a counterbalanced order, a normoxic and a hypoxic (partial pressure of oxygen: similar to 12 kPa) hand cold provocation (consisting of a 30-min immersion in 8 degrees C water), while immersed to the chest either in 21 degrees C [cold trials; 0.5 degrees C fall in rectal temperature (T-rec) from individual preimmersion values], or in 35.5 degrees C water, or while exposed to 27 degrees C air. The duration of the trials was kept constant in each breathing condition. Physiological (T-rec, skin temperature, cutaneous vascular conductance, oxygen uptake) and perceptual (thermal sensation and comfort, local pain, affective valence) reactions were monitored continually. Hypoxia accelerated the drop in T-rec by similar to 14 min (P = 0.06, d = 0.67). In the air-exposure trials, hypoxia did not alter finger perfusion during the local cooling. whereas it impaired the finger rewarming response following the cooling (P < 0.01). During the 35.5 degrees C immersion, the finger vasomotor tone was enhanced, especially in hypoxia (P = 0.01). Mild hypothermia aggravated finger vasoconstriction instigated by local cooling (P < 0.01), but the response did not differ between the two breathing conditions (P > 0.05). Hypoxia tended to attenuate the sensation of coldness (P = 0.10, r = 0.40) and thermal discomfort (P = 0.09, r = 0.46) in the immersed hand. Both in normoxia and hypoxia, the whole body thermal state dictates the cutaneous vasomotor reactivity to localized cold stimulus.

  • 16.
    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.

  • 17.
    Keramidas, Michail
    et al.
    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.
    Mekjavic, Igor B.
    Eiken, Ola
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Environmental Physiology.
    Interactions of mild hypothermia and hypoxia on finger vasoreactivity to local cold stress2019In: American Journal of Physiology. Regulatory Integrative and Comparative Physiology, ISSN 0363-6119, E-ISSN 1522-1490Article in journal (Refereed)
  • 18.
    Kölegård, Roger
    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.
    Da Silva, Cristina
    Department of Physiology, Karolinska University Hospital, Stockholm, Sweden.
    Siebenmann, Christoph
    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.
    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.
    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.
    Cardiac performance is influenced by rotational changes of position in the transversal plane, both in the horizontal and 60° 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.

  • 19.
    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
    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.
    Hjärtats minutvolym vid olika kroppspositioner2018Conference paper (Refereed)
  • 20.
    Machado-Moreira, Christiano
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH).
    Norrbrand, Lena
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Environmental Physiology.
    Grönkvist, Mikael
    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.
    Thermoregulation upon transition from exercise in a warm environment to exposure to a markedly cold environment; effects of a ventilated vest2018In: Proceedings from Physiology and Pharmacology Annual Scientific Meeting, 2018, 2018Conference paper (Refereed)
  • 21. McDonnell, Adam C.
    et al.
    Eiken, Ola
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Environmental Physiology.
    Frings-Meuthen, Petra
    Rittweger, Joern
    Mekjavic, Igor B.
    The LunHab project: Muscle and bone alterations in male participants following a 10 day lunar habitat simulation.2019In: Experimental Physiology, ISSN 0958-0670, E-ISSN 1469-445X, Vol. 104, no 8, p. 1250-1261Article in journal (Refereed)
    Abstract [en]

    NEW FINDINGS: What is the central question of this study? It is well established that muscle and bone atrophy in conditions of inactivity or unloading, but there is little information regarding the effect of a hypoxic environment on the time course of these deconditioning physiological systems. What is the main finding and its importance? The main finding is that a horizontal 10 day bed rest in normoxia results in typical muscle atrophy, which is not aggravated by hypoxia. Changes in bone mineral content or in metabolism were not detected after either normoxic or hypoxic bed rest.

    ABSTRACT: Musculoskeletal atrophy constitutes a typical adaptation to inactivity and unloading of weightbearing bones. The reduced-gravity environment in future Moon and Mars habitats is likely to be hypobaric hypoxic, and there is an urgent need to understand the effect of hypoxia on the process of inactivity-induced musculoskeletal atrophy. This was the principal aim of the present study. Eleven males participated in three 10 day interventions: (i) hypoxic ambulatory confinement; (ii) hypoxic bed rest; and (iii) normoxic bed rest. Before and after the interventions, the muscle strength (isometric maximal voluntary contraction), mass (lean mass, by dual-energy X-ray absorptiometry), cross-sectional area and total bone mineral content (determined with peripheral quantitative computed tomography) of the participants were measured. Blood and urine samples were collected before and on the 1st, 4th and 10th day of the intervention and analysed for biomarkers of bone resorption and formation. There was a significant reduction in thigh and lower leg muscle mass and volume after both normoxic and hypoxic bed rests. Muscle strength loss was proportionately greater than the loss in muscle mass for both thigh and lower leg. There was no indication of bone loss. Furthermore, the biomarkers of resorption and formation were not affected by any of the interventions. There was no significant effect of hypoxia on the musculoskeletal variables. Short-term normoxic (10 day) bed rest resulted in muscular deconditioning, but not in the loss of bone mineral content or changes in bone metabolism. Hypoxia did not modify these results.

  • 22.
    McDonnell, Adam C.
    et al.
    Jozef Stefan Inst, Jozef Stefan Int Postgrad Sch, Ljubljana, Slovenia..
    Stavrou, Nektarios A. M.
    ASPETAR Orthopaed & Sports Med Hosp, Doha, Qatar..
    Eiken, Ola
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Environmental Physiology.
    Mekjavic, Igor B.
    Jozef Stefan Inst, Ljubljana, Slovenia..
    The Effect Of A Live-high Train-high Regimen On Emotional State2015In: Medicine & Science in Sports & Exercise, ISSN 0195-9131, E-ISSN 1530-0315, Vol. 47, no 5, p. 608-608Article in journal (Other academic)
  • 23.
    Norrbrand, Lena
    et al.
    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.
    Keramidas, Michail E.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Environmental Physiology.
    Mekjavic, Igor B.
    Department of Automation, Robotics and Biocybernetics, Jozef Stefan Institute.
    Eiken, Ola
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Environmental Physiology.
    Finger- and toe-temperature responses to local cooling and rewarming have limited predictive value identifying susceptibility to local cold injury – a cohort study in military cadets2019In: Applied Ergonomics, ISSN 0003-6870, E-ISSN 1872-9126Article in journal (Refereed)
  • 24.
    Rosen, Anders
    et al.
    Sahlgrens Univ Hosp, Dept Anesthesia & Intens Care Med, Gothenburg, Sweden..
    Oscarsson, Nicklas
    Angered Hosp, Dept Surg, Gothenburg, Sweden..
    Kvarnstrom, Andreas
    Sahlgrens Univ Hosp, Dept Anesthesia & Intens Care Med, Gothenburg, Sweden..
    Gennser, Mikael
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Environmental Physiology.
    Sandstrom, Goran
    Swedish Armed Forces, Ctr Def Med, Gothenburg, Sweden..
    Blennow, Kaj
    Sahlgrens Univ Hosp, Clin Neurochem Lab, Gothenburg, Sweden.;Univ Gothenburg, Sahlgrenska Acad, Dept Psychiat & Neurochem, Molndal, Sweden..
    Seeman-Lodding, Helen
    Sahlgrens Univ Hosp, Dept Anesthesia & Intens Care Med, Gothenburg, Sweden..
    Zetterberg, Henrik
    Sahlgrens Univ Hosp, Clin Neurochem Lab, Gothenburg, Sweden.;Univ Gothenburg, Sahlgrenska Acad, Dept Psychiat & Neurochem, Molndal, Sweden.;UCL Inst Neurol, Dept Neurodegenerat Dis, London, England.;UCL, UK Dementia Res Inst, London, England..
    Serum tau concentration after diving - an observational pilot study2019In: Diving and Hyperbaric Medicine, ISSN 1833-3516, Vol. 49, no 2, p. 88-95, article id PMID 31177514Article in journal (Refereed)
    Abstract [en]

    Introduction: Increased concentrations of tau protein are associated with medical conditions involving the central nervous system, such as Alzheimer's disease, traumatic brain injury and hypoxia. Diving, by way of an elevated ambient pressure, can affect the nervous system, however it is not known whether it causes a rise in tau protein levels in serum. A prospective observational pilot study was performed to investigate changes in tau protein concentrations in serum after diving and also determine their relationship, if any, to the amount of inert gas bubbling in the venous blood. Methods: Subjects were 10 navy divers performing one or two dives per day, increasing in depth, over four days. Maximum dive depths ranged from 52-90 metres' sea water (msw). Air or trimix (nitrogen/oxygen/helium) was used as the breathing gas and the oxygen partial pressure did not exceed 160 kPa. Blood samples taken before the first and after the last dives were analyzed. Divers were monitored for the presence of venous gas emboli (VGE) at 10 to 15 minute intervals for up to 120 minutes using precordial Doppler ultrasound. Results: Median tau protein before diving was 0.200 pg.mL(-1)(range 0.100 to 1.10 pg.mL(-1)) and after diving was 0.450 pg.mL(-1) (range 0.100 to 1.20 pg.mL(-1); P = 0.016). Glial fibrillary acidic protein and neurofilament light protein concentrations analyzed in the same assay did not change after diving. No correlation was found between serum tau protein concentration and the amount of VGE. Conclusion: Repeated diving to between 52-90 msw is associated with a statistically significant increase in serum tau protein concentration, which could indicate neuronal stress.

  • 25. Rullman, Eric
    et al.
    Fernandez-Gonzalo, Rodrigo
    Mekjavić, Igor B.
    Gustafsson, Thomas
    Eiken, Ola
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Environmental Physiology.
    Mef2 as upstream regulator of the transcriptome signature in human skeletal muscle during unloading2018In: American Journal of Physiology. Regulatory Integrative and Comparative Physiology, ISSN 0363-6119, E-ISSN 1522-1490Article in journal (Refereed)
    Abstract [en]

    Our understanding of skeletal muscle structural and functional alterations during unloading has increased in recent decades, yet the molecular mechanisms underpinning these changes have only started to be unraveled. The purpose of the current investigation was to assess changes in skeletal muscle gene expression after 21 days of bed rest, with a particular focus on predicting upstream regulators of muscle disuse. Additionally, the association between differential microRNA expression and the transcriptome signature of bed rest were investigated. mRNAs from m. vastus lateralis biopsies obtained from 12 men before and after the bed rest were analyzed using a microarray. There were 54 significantly up-regulated probesets after bed rest, whereas 103 probesets were down-regulated (FDR 10%; fold-change cut-off ≥1.5). Amongst the up-regulated genes, transcripts related to denervation-induced alterations in skeletal muscle were identified, e.g. CHRND and perinatal myosin. The most down-regulated transcripts were functionally enriched for mitochondrial genes and genes involved in mitochondrial biogenesis, followed by a large number of contractile fiber components. Upstream regulator-analysis identified a robust inhibition of the MEF2 family, in particular MEF2C, which was suggested to act upstream of several key down-regulated genes, most notably PGC-1α/PPARs and CRSP3. Only a few microRNAs were identified as playing a role in the overall transcriptome picture induced by sustained bed rest. Our results suggest that the MEF2 family is a key regulator underlying the transcriptional signature of bed rest, and hence ultimately also skeletal muscle alterations induced by systemic unloading in humans.

  • 26.
    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.

  • 27.
    Silvanius, Marten
    et al.
    Swedish Armed Forces, Diving & Naval Med Ctr, Karlskrona, Sweden.;Blekinge Inst Technol, Karlskrona, Sweden..
    Mitchell, Simon J.
    Univ Auckland, Dept Anaesthesiol, Auckland, New Zealand..
    Pollock, Neal W.
    Univ Laval Quebec, Dept Kinesiol, Quebec City, PQ, Canada..
    Franberg, Oskar
    Blekinge Inst Technol, Karlskrona, Sweden..
    Gennser, Mikael
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Environmental Physiology.
    Linden, Jerry
    Swedish Armed Forces, Diving & Naval Med Ctr, Karlskrona, Sweden..
    Mesley, Peter
    Lust Rust Diving Expedit, Auckland, New Zealand..
    Gant, Nicholas
    Univ Auckland, Dept Exercise Sci, Auckland, New Zealand..
    The performance of 'temperature stick' carbon dioxide absorbent monitors in diving rebreathers2019In: Diving and Hyperbaric Medicine, ISSN 1833-3516, Vol. 49, no 1, p. 48-56, article id PMID 30856667Article in journal (Refereed)
    Abstract [en]

    Introduction: Diving rebreathers use canisters containing soda lime to remove carbon dioxide (CO2) from expired gas. Soda lime has a finite ability to absorb CO2. Temperature sticks monitor the exothermic reaction between CO2 and soda lime to predict remaining absorptive capacity. The accuracy of these predictions was investigated in two rebreathers that utilise temperature sticks. Methods: Inspiration and rEvo rebreathers filled with new soda lime were immersed in water at 19 degrees C and operated on mechanical circuits whose ventilation and CO2-addition parameters simulated dives involving either moderate exercise (6 MET) throughout (mod-ex), or 90 minutes of 6 MET exercise followed by 2 MET exercise (low-ex) until breakthrough (inspired PCO2 [PiCO2] = 1 kPa). Simulated dives were conducted at surface pressure (sea-level) (low-ex: Inspiration, n = 5; rEvo, n = 5; mod-ex: Inspiration, n = 7, rEvo, n = 5) and at 3-6 metres' sea water (msw) depth (mod-ex protocol only: Inspiration, n = 8; rEvo, n = 5). Results: Operated at surface pressure, both rebreathers warned appropriately in four o five low-ex tests but failed to do so in the 12 mod-ex tests. At 3-6 msw depth, warnings preceded breakthrough in 11 of 13 mod-ex tests. The rEvo warned conservatively in all five tests (approximately 60 minutes prior). Inspiration warnings immediately preceded breakthrough in six of eight tests, but were marginally late in one test and 13 minutes late in another. Conclusion: When operated at even shallow depth, temperature sticks provided timely warning of significant CO2 breakthrough in the scenarios examined. They are much less accurate during simulated exercise at surface pressure.

  • 28.
    Sotiridis, Alexander
    et al.
    Jozef Stefan Institute, Ljubljana.
    Debevec, Tadej
    Jozef Stefan Institute, Ljubljana.
    Ciuha, Ursa
    Jozef Stefan Institute, Ljubljana.
    Eiken, Ola
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Environmental Physiology. Jozef Stefan Institute, Ljubljana.
    Mekjavic, Igor B
    Jozef Stefan Institute, Ljubljana.
    Heat acclimation augments peak power output and thermoregulatory responses in thermoneutral but not hypoxic conditions2018In: Proceedings from 23rd annual congress of the European College of Sport Science, in Dublin, 2018, 2018Conference paper (Refereed)
  • 29.
    Sotiridis, Alexander
    et al.
    Jozef Stefan Institute, Ljubljana.
    Debevec, Tadej
    Jozef Stefan Institute, Ljubljana.
    Ciuha, Ursa
    Jozef Stefan Institute, Ljubljana.
    Mcdonnell, Adam
    Jozef Stefan Institute, Ljubljana.
    Miliotis, Panagiotis
    School of Physical Education and Sports Science, National and Kapodistrian University of Athen.
    Koskolou, Maria
    School of Physical Education and Sports Science, National and Kapodistrian University of Athen.
    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 Institute, Ljubljana.
    Separate and combined effects of heat and hypoxic acclimation on temperature regulation and exercise performance2018In: Proceedings from Physiology and Pharmacology in Temperature Regulation Annual Scientific Meeting, 2018, 2018Conference paper (Refereed)
  • 30.
    Sotiridis, Alexandros
    et al.
    Jozef Stefan Institute, Ljubljana.
    Debevec, Tadej
    Jozef Stefan Institute, Ljubljana.
    Ciuha, Urša
    Jozef Stefan Institute, Ljubljana.
    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 Institute, Ljubljana.
    Heat acclimation does not affect maximal aerobic power in thermoneutral normoxic or hypoxic conditions2019In: Experimental Physiology, ISSN 0958-0670, E-ISSN 1469-445X, Vol. 104, p. 1250-1261Article in journal (Refereed)
    Abstract [en]

    What is the central question of this study? Controlled-hyperthermia heat acclimation protocols induce an array of thermoregulatory and cardiovascular adaptations that facilitate exercise in hot conditions. We investigated whether this ergogenic potential can be transferred to thermoneutral normoxic or hypoxic exercising conditions. What is the main finding and its importance? We show that heat acclimation did not affect maximal cardiac output or maximal aerobic power in thermoneutral normoxic/hypoxic conditions. Heat acclimation augmented the sweating response in thermoneutral normoxic conditions. The cross-adaptation theory according to which heat acclimation could facilitate hypoxic exercise capacity is not supported by our data. ABSTRACT: Heat acclimation (HA) mitigates heat-induced decrements in maximal aerobic power (V̇O2peak ) and augments exercise thermoregulatory responses in the heat. Whether this beneficial effect of HA is observed in hypoxic or thermoneutral conditions remains unresolved. We explored the effects of HA on exercise cardiorespiratory and thermoregulatory responses in normoxic, hypoxic, and hot conditions. Twelve males (V̇O2peak 54.7(5.7) mL·kg-1 ·min-1 ) participated in a HA protocol comprising 10 daily 90-min controlled-hyperthermia (target rectal temperature, Tre  = 38.5 °C) exercise sessions. Before and after HA, we determined V̇O2peak in thermoneutral normoxic (NOR), thermoneutral hypoxic (13.5% Fi O2 ; HYP) and hot (35 °C, 50% RH; HE) conditions in a randomized and counterbalanced order. Preceding each maximal cycling test, a 30-min steady-state exercise at 40% of the NOR peak power output (Wpeak ) was employed to evaluate thermoregulatory responses. HA induced the expected adaptations in HE: reduced Tre and submaximal heart rate (HR), enhanced sweating response and expanded plasma volume. However, HA did not affect V̇O2peak or maximal cardiac output (COmax ) (P = 0.61). Wpeak was increased post-HA in NOR (P < 0.001) and HE (P < 0.001) by 41 ± 21 and 26 ± 22 W, respectively but not in HYP (P = 0.14). Gross mechanical efficiency was higher (P = 0.004) whereas resting Tre and sweating thresholds were lower (P < 0.01) post-HA across environments. Nevertheless, the gain of the sweating response decreased (P = 0.05) in HYP. In conclusion, our data do not support a beneficial cross-over effect of HA on V̇O2peak in normoxic or hypoxic conditions. This article is protected by copyright.

  • 31. Sotiridis, Alexandros
    et al.
    Debevec, Tadej
    McDonnell, Adam C.
    Ciuha, Ursa
    Eiken, Ola
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Environmental Physiology.
    Mekjavic, Igor B
    Exercise cardiorespiratory and thermoregulatory responses in normoxic, hypoxic and hot environment following 10-day continuous hypoxic exposure2018In: Journal of applied physiology, ISSN 8750-7587, E-ISSN 1522-1601, Vol. 125, no 4, p. 1284-1295Article in journal (Refereed)
    Abstract [en]

    We examined the effects of acclimatization to normobaric hypoxia on aerobic performance and exercise thermoregulatory responses under normoxic, hypoxic and hot conditions. Twelve males performed tests of maximal oxygen uptake (V̇O2max) in normoxic (NOR), hypoxic (13.5% FiO2; HYP) and hot (35℃, 50% RH; HE) conditions in a randomized manner before and after a 10-day continuous normobaric hypoxic exposure (FiO2 = 13.65(0.35)%, PiO2 = 87(3) mmHg). The acclimatization protocol included daily exercise (60min @ 50% hypoxia-specific peak power output, Wpeak). All maximal tests were preceded by a steady-state exercise (30 min at 40% Wpeak) to assess the sweating response. Hematological data were assessed from venous blood samples obtained before and after acclimatization. V̇O2max increased by 10.7% (P = 0.002) and 7.9% (P = 0.03) from pre- to post-acclimatization in NOR and HE, respectively, whereas no differences were found in HYP (pre: 39.9(3.8) vs post: 39.4(5.1) mL.kg-1.min-1, P = 1.0). However, the increase in V̇O2max did not translate into increased Wpeak in either NOR or HE. Maximal heart rate and ventilation remained unchanged following acclimatization. Νo differences were noted in the sweating gain and thresholds independent of the acclimatization or environmental conditions. Hypoxic acclimatization markedly increased hemoglobin (P &lt; 0.001), hematocrit (P &lt; 0.001) and extracellular HSP72 (P = 0.01). These data suggest that 10 days of normobaric hypoxic acclimatization combined with moderate-intensity exercise training improves V̇O2max in NOR and HE, but does not seem to affect exercise performance or thermoregulatory responses in any of the tested environmental conditions.

  • 32. Stavrou, N. A. M.
    et al.
    Debevec, T.
    Eiken, Ola
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Environmental Physiology.
    Mekjavic, I. B.
    Hypoxia worsens affective responses and feeling of fatigue during prolonged bed rest2018In: Frontiers in Psychology, ISSN 1664-1078, E-ISSN 1664-1078, Vol. 9, no MAR, article id 362Article in journal (Refereed)
    Abstract [en]

    Previous research, although limited, suggests that both hypoxia and bed rest influence psychological responses by exaggerating negative psychological responses and attenuating positive emotions. The present study investigated the effect of a 21-day prolonged exposure to normobaric hypoxia and bed rest on affective responses and fatigue. Eleven healthy participants underwent three 21-day interventions using a cross-over design: (1) normobaric hypoxic ambulatory confinement (HAMB), (2) normobaric hypoxic bed rest (HBR) and (3) normoxic bed rest (NBR). Affective and fatigue responses were investigated using the Activation Deactivation Adjective Check List, and the Multidimensional Fatigue Inventory, which were completed before (Pre), during (Day 7, Day 14, and Day 21) and after (Post) the interventions. The most negative psychological profile appeared during the HBR intervention. Specifically, tiredness, tension, general and physical fatigue significantly increased on days 7, 14, and 21, as well as at Post. After the HBR intervention, general and physical fatigue remained higher compared to Pre values. Additionally, a deterioration of psychological responses was also noted following HAMB and NBR. In particular, both hypoxia and BR per se induced subjective fatigue and negative affective responses. BR seems to exert a moderate negative effect on the sensation of fatigue, whereas exercise attenuates the negative effects of hypoxia as noted during the HAMB condition. In conclusion, our data suggest that the addition of hypoxia to bed rest-induced inactivity significantly worsens affective responses and feeling of fatigue.

  • 33. Stavrou, Nektarios A. M.
    et al.
    Debevec, Tadej
    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.
    Hypoxia Exacerbates Negative Emotional State during Inactivity: The Effect of 21 Days Hypoxic Bed Rest and Confinement2018In: Frontiers in Physiology, ISSN 1664-042X, E-ISSN 1664-042X, Vol. 9, article id 26Article in journal (Refereed)
    Abstract [en]

    Hypoxia and confinement have both been shown to influence emotional state. It is envisaged that the inhabitants of future planetary habitats will be exposed to concomitant confinement, reduced gravity and hypoxia. We examined the independent and combined effects of a 21-day inactivity/unloading and normobaric hypoxia under confined conditions on various psychological factors. Eleven healthy men participated in three 21-day experimental campaigns designed in a cross-over manner (1) Normobaric hypoxic ambulatory confinement, (2) Normobaric hypoxic bed rest and (3) Normobaric normoxic bed rest. The Profile of Mood States, and the Positive and Negative Affect Schedule were employed to assess the participants' psychological responses before (Pre), during (Day 7, Day 14, and Day 21) and after (Post) the confinements. The most negative psychological profile appeared on days 14 and 21 of the hypoxic bed rest campaign. A significant increase in depression, tension, and confusion was noted on days 14 and 21 of the hypoxic bed rest condition. Concomitantly, a decrease, albeit not statistically significant, in positive psychological responses was observed. The psychological profile returned to the initial level at Post following all confinements. These data suggest that the combined effect of hypoxia and bed rest induced the most negative effects on an individual's mood. However, significant intra- and inter-individual differences in psychological responses were noted and should be taken into consideration.

  • 34. Strewe, C.
    et al.
    Zeller, R.
    Feuerecker, M.
    Hoerl, M.
    Matzel, S.
    Kumprej, I.
    Crispin, A.
    Johannes, B.
    Debevec, T.
    Mekjavic, I. B.
    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.
    Thiel, M.
    Schelling, G.
    Choukèr, A.
    PlanHab Study: Consequences of combined normobaric hypoxia and bed rest on adenosine kinetics2018In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 8, no 1, article id 1762Article in journal (Refereed)
    Abstract [en]

    Adenosine plays a role in the energy supply of cells and provokes differential, hormone-like functions in circulating cells and various tissues. Its release is importantly regulated by oxygen tension. This renders adenosine and its kinetics interesting to investigate in humans subjected to low oxygen conditions. Especially for space exploration scenarios, hypoxic conditions - together with reduced gravity - represent two foreseen living conditions when planning manned long-duration space missions or planetary habitats. The PlanHab study investigated microgravity through inactivity in bed rest and normobaric hypoxia to examine their independent or combined effect on adenosine and its kinetics. Healthy male subjects (n = 14) completed three 21-day interventions: hypoxic bed rest (HBR); hypoxic ambulatory confinement (HAMB); normoxic bed rest (NBR). The interventions were separated by 4 months. Our hypothesis of a hypoxia-triggered increase in adenosine was confirmed in HAMB but unexpectedly also in NBR. However, the highest adenosine levels were noted following HBR. Furthermore, the percentage of hemolysis was elevated in HBR whereas endothelial integrity markers stayed low in all three interventions. In summary, these data suggest that neocytolysis accounts for these effects while we could reduce evidence for microcirculatory changes.

  • 35.
    Sundblad, Patrik
    et al.
    Karolinska Inst, Dept Lab Med, Clin Physiol, SE-14186 Stockholm, Sweden.;Karolinska Univ Hosp, Dept Clin Physiol, SE-14186 Stockholm, Sweden..
    Kölegård, Roger
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Environmental Physiology.
    Rullman, Eric
    Karolinska Inst, Dept Lab Med, Clin Physiol, SE-14186 Stockholm, Sweden.;Karolinska Univ Hosp, Dept Clin Physiol, SE-14186 Stockholm, Sweden..
    Gustafsson, Thomas
    Karolinska Inst, Dept Lab Med, Clin Physiol, SE-14186 Stockholm, Sweden.;Karolinska Univ Hosp, Dept Clin Physiol, SE-14186 Stockholm, Sweden..
    Effects of training with flow restriction on the exercise pressor reflex2018In: European Journal of Applied Physiology, ISSN 1439-6319, E-ISSN 1439-6327, Vol. 118, no 9, p. 1903-1909Article in journal (Refereed)
    Abstract [en]

    We hypothesized that 5 weeks of endurance training with blood flow restriction (R-training), providing relative ischemia and stimulation of the muscle chemoreflex, would decrease the exercise pressor reflex (EPR) when compared to training with the same workload in a free-flow condition (NR-training). 10 subjects performed one-leg knee-extension training four times a week during a 5-week period. Both legs were trained with identical workload, with one leg being trained during flow-restriction induced by lower body positive pressure. The EPR was assessed by measuring the increase in heart rate (HR) and mean arterial pressure (MAP) during an isometric knee extension of 35% of max torque for 90 s, this was done before (C), and after training in each leg (R and NR, respectively). At the end of isometric contraction, the increase in mean AP (MAP) in the NR-trained leg and in the control condition were 41 +/- 4 and 38 +/- 4 mmHg, respectively, whereas the increase in the R-trained leg was 30 +/- 4 mmHg (p < 0.05 R vs C and NR), corresponding to a decrease of about 25%. A similar patter was observed with respect to responses in HR, where the increase was 28 +/- 3 and 28 +/- 3 bpm in the NR and C, and 22 +/- 4 in the R condition (p < 0.05 R vs C and NR). Peripheral metabolic changes induced by relative ischemia are important in modifying the EPR in response to exercise training.

  • 36.
    Ånell, Rickard
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Environmental Physiology.
    Grönkvist, Mikael
    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.
    Gennser, Mikael
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Environmental Physiology.
    Is there a safe altitude to compress venous gas emboli after simulated high-altitude flying?2018In: Proceedings from Swedish Aeronautical Medical Associations Annual Scientific Meeting, 2018, 2018Conference paper (Refereed)
  • 37.
    Ånell, Rickard
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Environmental Physiology. Swedish Aerospace Physiology Centre.
    Grönkvist, Mikael
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Environmental Physiology. Swedish Aerospace Physiology Centre.
    Eiken, Ola
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Environmental Physiology. Swedish Aerospace Physiology Centre.
    Gennser, Mikael
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Environmental Physiology. Swedish Aerospace Physiology Centre.
    Nitrogen Washout and Venous Gas Emboli During Sustained vs. Discontinuous High-Altitude Exposures2019In: Aerospace Medicine and Human Performance, ISSN 2375-6314, E-ISSN 2375-6322, Vol. 90, no 6, p. 524-530Article in journal (Refereed)
    Abstract [en]

    INTRODUCTION: The frequency of long-duration, high-altitude missions with fighter aircraft is increasing, which may increase the incidence of decompression sickness (DCS).The aim of the present study was to compare decompression stress during simulated sustained high-altitude flying vs. high-altitude flying interrupted by periods of moderate or marked cabin pressure increase. METHODS: The level of venous gas emboli (VGE) was assessed from cardiac ultrasound images using the 5-degree Eftedal-Brubakk scale. Nitrogen washout/uptake was measured using a closed circuit rebreather. Eight men were investigated in three conditions: one 80-min continuous exposure to a simulated cabin altitude of A) 24,000 ft, or four 20-min exposures to 24,000 ft interspersed by three 20-min intervals at 8) 20,000 ft or C) 900 ft. RESULTS: A and B induced marked and persistent VGE, With peak bubble scores of [median (range)]: A 2.5 (1-3); B: 3.5 (2-4). Peak VGE score was less in C [1.0(1-2),P < 0.01]. Condition A exhibitedan initially high and exponentially decaying rate of nitrogen washout. In C the washout rate was similar in each period at 24,000 ft, and the nitrogen uptake rate was similar during each 900-ft exposure. B exhibited nitrogen washout during each period at 24,000 ft and the initial period at 20,000 ft, but on average no washout or uptake during the last period at 20,000 ft. DISCUSSION: Intermittent reductions of cabin altitude from 24,000 to 20,000 ft do not appear to alleviate the DCS risk, presumably because the pressure increase is not sufficient to eliminate VGE. The nitrogen washout/uptake rate did not reflect DCS risk in the present exposures.

  • 38. Šarabon, N.
    et al.
    Mekjavić, I. B.
    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.
    Babič, J.
    The effect of bed rest and hypoxic environment on postural balance and trunk automatic (re)actions in young healthy males2018In: Frontiers in Physiology, ISSN 1664-042X, E-ISSN 1664-042X, Vol. 9, no January, article id 27Article in journal (Refereed)
    Abstract [en]

    Prolonged inactivity, such as bed rest induces several detrimental changes within a short timeframe. Impaired postural balance and responses of trunk muscles to (un)expected perturbations were both shown to be impaired after bed rest. Certain populations (e.g., astronauts) are exposed to hypoxic environment in addition to inactivity, similar to bed rest. While the isolated negative effects of hypoxia on postural balance have been observed before, no study to date has examined the combined effects of hypoxia and bed rest on postural balance or trunk muscle responses. In this study, we examined the effects of 21-day exposure to three conditions: (i) bed rest in hypoxic environment (HBR), (ii) bed rest in normoxic environment (NBR), and (iii) ambulatory hypoxic environment (HAMB). Fourteen healthy male subjects crossed over between conditions in a randomized order, with a 4-month break between conditions to ensure full recovery. Most body sway parameters indicated a similar deterioration of postural balance following both HBR and NBR. Similarly, both anticipatory and reactive responses of the trunk muscles (m. erector spinae and m. multifidus) were impaired after HBR and NBR to a similar degree and mostly unchanged after HAMB. Certain body sway parameters were impaired after HAMB, confirming that hypoxia alone can undermine postural balance. On the other hand, some trunk responses were improved after HAMB. In conclusion, the results of our study confirmed previous findings on negative effects of bed rest, but showed little or no additional effect of hypoxia during bed rest. Physical activity during bed rest is encouraged to preserve neuromuscular functions of the trunk. While the HBR condition in our study resembled conditions during space missions, our results could be relevant to other populations, such as patients with pulmonary diseases exposed to bed rest.

  • 39. Šket, R.
    et al.
    Debevec, T.
    Kublik, S.
    Schloter, M.
    Schoeller, A.
    Murovec, B.
    Mikuš, K. V.
    Makuc, D.
    Pečnik, K.
    Plavec, J.
    Mekjavić, I. B.
    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.
    Prevoršek, Z.
    Stres, B.
    Intestinal metagenomes and metabolomes in healthy young males: Inactivity and hypoxia generated negative physiological symptoms precede microbial dysbiosis2018In: Frontiers in Physiology, ISSN 1664-042X, E-ISSN 1664-042X, Vol. 9, no Mars, article id 198Article in journal (Refereed)
    Abstract [en]

    We explored the metagenomic, metabolomic and trace metal makeup of intestinal microbiota and environment in healthy male participants during the run-in (5 day) and the following three 21-day interventions: normoxic bedrest (NBR), hypoxic bedrest (HBR) and hypoxic ambulation (HAmb) which were carried out within a controlled laboratory environment (circadian rhythm, fluid and dietary intakes, microbial bioburden, oxygen level, exercise). The fraction of inspired O2 (FiO2) and partial pressure of inspiredO2 (PiO2) were 0.209 and 133.1 ± 0.3 mmHg for the NBR and 0.141 ± 0.004 and 90.0 ± 0.4 mmHg (~4,000 m simulated altitude) for HBR and HAmb interventions, respectively. Shotgun metagenomes were analyzed at various taxonomic and functional levels, 1H-and 13C-metabolomes were processed using standard quantitative and human expert approaches, whereas metals were assessed using X-ray fluorescence spectrometry. Inactivity and hypoxia resulted in a significant increase in the genus Bacteroides in HBR, in genes coding for proteins involved in iron acquisition and metabolism, cell wall, capsule, virulence, defense and mucin degradation, such as beta-galactosidase (EC3.2.1.23), α-L-fucosidase (EC3.2.1.51), Sialidase (EC3.2.1.18), and α-N-acetylglucosaminidase (EC3.2.1.50). In contrast, the microbial metabolomes, intestinal element and metal profiles, the diversity of bacterial, archaeal and fungal microbial communities were not significantly affected. The observed progressive decrease in defecation frequency and concomitant increase in the electrical conductivity (EC) preceded or took place in absence of significant changes at the taxonomic, functional gene, metabolome and intestinal metal profile levels. The fact that the genus Bacteroides and proteins involved in iron acquisition and metabolism, cell wall, capsule, virulence and mucin degradation were enriched at the end of HBR suggest that both constipation and EC decreased intestinal metal availability leading to modified expression of co-regulated genes in Bacteroides genomes. Bayesian network analysis was used to derive the first hierarchical model of initial inactivity mediated deconditioning steps over time. The PlanHab wash-out period corresponded to a profound life-style change (i.e., reintroduction of exercise) that resulted in stepwise amelioration of the negative physiological symptoms, indicating that exercise apparently prevented the crosstalk between the microbial physiology, mucin degradation and proinflammatory immune activities in the host.

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