| 1. |
- Debevec, T., et al.
(författare)
-
No evidence for the “normobaric oxygen paradox”
- 2011
-
Ingår i: Medicine & Science in Sports & Exercise. - 0195-9131 .- 1530-0315. ; 43:S5, s. 151-151
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
|
|
| 2. |
|
|
| 3. |
|
|
| 4. |
- Keramidas, Michail E., et al.
(författare)
-
Acute normobaric hyperoxia transiently attenuates plasma erythropoietin concentration in healthy males : evidence against the 'normobaric oxygen paradox' theory
- 2011
-
Ingår i: Acta Physiologica. - : Wiley-Blackwell. - 1748-1708 .- 1748-1716. ; 202:1, s. 91-98
-
Tidskriftsartikel (refereegranskat)abstract
- Aim: The purpose of the present study was to evaluate the 'normobaric oxygen paradox' theory by investigating the effect of a 2-h normobaric O(2) exposure on the concentration of plasma erythropoietin (EPO). Methods: Ten healthy males were studied twice in a single-blinded counterbalanced crossover study protocol. On one occasion they breathed air (NOR) and on the other 100% normobaric O(2) (HYPER). Blood samples were collected Pre, Mid and Post exposure; and thereafter, 3, 5, 8, 24, 32, 48, 72 and 96 h, and 1 and 2 weeks after the exposure to determine EPO concentration. Results: The concentration of plasma erythropoietin increased markedly 8 and 32 h after the NOR exposure (approx. 58% and approx. 52%, respectively, P < 0.05) as a consequence of its natural diurnal variation. Conversely, the O(2) breathing was followed by approx. 36% decrement of EPO 3 h after the exposure (P < 0.05). Moreover, EPO concentration was significantly lower in HYPER than in the NOR condition 3, 5 and 8 h after the breathing intervention (P < 0.05). Conclusion: In contrast to the 'normobaric oxygen paradox' theory, the present results indicate that a short period of normobaric O(2) breathing does not increase the EPO concentration in aerobically fit healthy males. Increased O(2) tension suppresses the EPO concentration 3 and 5 h after the exposure; thereafter EPO seems to change in a manner consistent with natural diurnal variation.
|
|
| 5. |
|
|
| 6. |
|
|
| 7. |
|
|
| 8. |
|
|
| 9. |
|
|
| 10. |
|
|
| 11. |
|
|
| 12. |
- Bertolotto, L, et al.
(författare)
-
phi phi associated production in (p)over-bar-p annihilation from JETSET
- 1996
-
Ingår i: PHYSICS OF ATOMIC NUCLEI. - : AMER INST PHYSICS. ; , s. 1444-1449
-
Konferensbidrag (refereegranskat)abstract
- The JETSET (PS202) experiment at CERN has studied the reaction (p) over bar p --> 4K(+/-) in the invariant-mass range from 2.15 to 2.43 GeV/c(2). The phi phi, phi K+K-, and 4K(+/-) cross sections have been measured, and a spin-parity analysis of the phi p
|
|
| 13. |
|
|
| 14. |
- Debevec, T., et al.
(författare)
-
Effects of prolonged hypoxia and bed rest on appetite and appetite-related hormones
- 2016
-
Ingår i: Appetite. - : Academic Press. - 0195-6663 .- 1095-8304. ; 107, s. 28-37
-
Tidskriftsartikel (refereegranskat)abstract
- Environmental hypoxia and inactivity have both been shown to modulate appetite. To elucidate the independent and combined effects of hypoxia and bed rest-induced inactivity on appetite-related hormones and subjective appetite, eleven healthy, non-obese males underwent three experimental interventions in a cross-over and randomized fashion: 1) Hypoxic confinement combined with daily moderate-intensity exercise (HAMB, FiO2 = 0.141 ± 0.004; PiO2 = 90.0 ± 0.4 mmHg) 2) Bed rest in normoxia (NBR, FiO2 = 0.209; PiO2 = 133.1 ± 0.3 mmHg) and 3) Bed rest in hypoxia (HBR, FiO2 = 0.141 ± 0.004; PiO2 = 90.0 ± 0.4 mmHg). A mixed-meal tolerance test (MTT), followed by an ad libitum meal were performed before (Pre) and after 16-days (Post) of each intervention. Composite satiety scores (CSS) during the MTT were calculated from visual analogue scores, while fasting and postprandial concentrations of total ghrelin, peptide YY (PYY), glucagon-like peptide-1 (GLP-1) and leptin were quantified from arterialized-venous samples. Postprandial CSS were significantly lower at Post compared to Pre in NBR only (P < 0.05) with no differences observed in ad libitum meal intakes. Postprandial concentrations and incremental area under the curve (AUC) for total ghrelin and PYY were unchanged following all interventions. Postprandial GLP-1 concentrations were only reduced at Post following HBR (P < 0.05) with resulting AUC changes being significantly lower compared to HAMB (P < 0.01). Fasting leptin was reduced following HAMB (P < 0.05) with no changes observed following NBR and HBR. These findings suggest that independently, 16-day of simulated altitude exposure (∼4000 m) and bed rest-induced inactivity do not significantly alter subjective appetite or ad libitum intakes. The measured appetite-related hormones following both HAMB and HBR point to a situation of hypoxia-induced appetite stimulation, although this did not reflect in higher ad libitum intakes. Clinical Trial Registration Number: NCT02293772.
|
|
| 15. |
|
|
| 16. |
- Debevec, T, et al.
(författare)
-
FemHab: Prooxidant/antioxidant balance during and following a 10-day hypoxic bed rest
- 2015
-
Konferensbidrag (refereegranskat)abstract
- Introduction:Inhabitants of the envisaged planetary habitats will be continuously exposed to reduced gravity and hypoxia. The combined effects of unloading and hypoxia on prooxidant/antioxidant balance are currently unknown.Methods:Healthy female participants underwent the following three, 10-day interventions: i) Normobaric normoxic bed-rest (NBR; n=11; FiO2=0.209) ii) Normobaric hypoxic ambulatory confinement (HAMB; n=9: FiO2~0.141), and iii) Normobaric hypoxic bed-rest (HBR; n=12; FiO2~0.141). Plasma oxidative stress [advanced oxidation protein products (AOPP) and nitrotyrosine], antioxidant markers [superoxide dismutase (SOD) and glutathione peroxidase (GPX)] and nitrites were determined before (Pre), during (Day 2, Day 6), immediately after (Post) and 24-hrs after (Post+1) each campaign.Results:Compared to Pre, the AOPP was only higher on Day 2, Day 6 and Post during the HBR and at Post during the NBR (P<0.05) while the nitrotyrosine was significantly reduced at Post+1 only during the HAMB (P<0.05). Higher levels of SOD were observed during the HAMB at Day 6 and Post+1whereas GPX was reduced at Day 6 and Post during the HBR. Nitrites were significantly higher at Post+1 in the HAMB both, compared to Pre and compared to HBR and NBR (P<0.05).Conclusion:These data suggest that the unloading-induced oxidative stress is exacerbated by exposure to simulated altitude of ~4000m. In addition, even habitual (low) physical activity, performed during hypoxic exposure, seems to blunt hypoxia-related oxidative stress via antioxidant system upregulation.
|
|
| 17. |
- Debevec, T, et al.
(författare)
-
Hematological responses to two different intermittent hypoxic training regimens
- 2009
-
Konferensbidrag (refereegranskat)abstract
- "Hypoxic training has been reported to enhance athletes’ altitude and sea-level performance by augmenting oxygen carrying capacity of the blood, as a consequence of increases in hematocrit and hemoglobin concentrations. However the effect of intermittent hypoxic training on hematological responses remains unresolved."This study investigated the effect of two intermittent hypoxic training regimens on the response of hematological indices. Healthy male Ss (N = 27) were equally assigned to a control group, a live low-train high (LL-TH) group, or a intermittent hypoxic exposure group. Ss performed a one-hour submaximal endurance exercise on a cycle ergometer, five days per week for four weeks, at an intensity corresponding to 50% of normoxic peak power output for the control and intermittent hypoxic exposure groups, and to 50% of hypoxic peak power output for the LL-TH group. Thus, all groups trained at the same relative work rate. The absolute work rate during training was 18-20 W lower for the LL-TH group compared to the other two groups. All groups lived at an altitude of ~300 m above sea level. The control and intermittent hypoxic exposure groups also trained at this altitude, whereas the LL-TH group trained in a hypoxic chamber, breathing a hypoxic mixture (FIO2=12%). In addition to the daily exercise training, the intermittent hypoxic exposure group also inspired a hypoxic gas mixture at rest, and prior to the cycle ergometry. The intermittent hypoxic training comprised breathing a hypoxic mixture during seven phases. Each phase consisted of five minutes of breathing a hypoxic mixture, followed by three minutes of breathing a normoxic gas mixture. Prior to, during, at the end, and 10 days after the training period, blood samples were taken from all Ss in order to measure hemoglobin, hematocrit, erythrocytes, ferritin, and transferrin concentrations.No significant differences were observed between groups in any measured hematological variables. Similarly, no significant differences were found within groups at the different testing periods.Implication. Although it has been reported that both LL-TH and intermittent hypoxic exposure protocols provide hematological benefits, that was not confirmed by this study. The tested protocols did not induce any changes in the measured hematological variables; therefore no improvements of the oxygen carrying capacity of the blood should be expected following this type of hypoxic training.
|
|
| 18. |
- Debevec, T., et al.
(författare)
-
Hypoxia aggravates inactivity-Related muscle wasting
- 2018
-
Ingår i: Frontiers in Physiology. - : Frontiers Media S.A.. - 1664-042X. ; 9:May
-
Tidskriftsartikel (refereegranskat)abstract
- 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.
|
|
| 19. |
- Debevec, T., et al.
(författare)
-
Moderate exercise blunts oxidative stress induced by normobaric hypoxic confinement
- 2014
-
Ingår i: Medicine & Science in Sports & Exercise. - 0195-9131 .- 1530-0315. ; 46:1, s. 33-41
-
Tidskriftsartikel (refereegranskat)abstract
- PURPOSE: Both acute hypoxia and physical exercise are known to increase oxidative stress. This randomized prospective trial investigated whether the addition of moderate exercise can alter oxidative stress induced by continuous hypoxic exposure. METHODS: Fourteen male participants were confined to 10-d continuous normobaric hypoxia (FIO2 = 0.139 ± 0.003, PIO2 = 88.2 ± 0.6 mm Hg, ∼4000-m simulated altitude) either with (HCE, n = 8, two training sessions per day at 50% of hypoxic maximal aerobic power) or without exercise (HCS, n = 6). Plasma levels of oxidative stress markers (advanced oxidation protein products [AOPP], nitrotyrosine, and malondialdehyde), antioxidant markers (ferric-reducing antioxidant power, superoxide dismutase, glutathione peroxidase, and catalase), nitric oxide end-products, and erythropoietin were measured before the exposure (Pre), after the first 24 h of exposure (D1), after the exposure (Post) and after the 24-h reoxygenation (Post + 1). In addition, graded exercise test in hypoxia was performed before and after the protocol. RESULTS: Maximal aerobic power increased after the protocol in HCE only (+6.8%, P < 0.05). Compared with baseline, AOPP was higher at Post + 1 (+28%, P < 0.05) and nitrotyrosine at Post (+81%, P < 0.05) in HCS only. Superoxide dismutase (+30%, P < 0.05) and catalase (+53%, P < 0.05) increased at Post in HCE only. Higher levels of ferric-reducing antioxidant power (+41%, P < 0.05) at Post and lower levels of AOPP (-47%, P < 0.01) at Post + 1 were measured in HCE versus HCS. Glutathione peroxidase (+31%, P < 0.01) increased in both groups at Post + 1. Similar erythropoietin kinetics was noted in both groups with an increase at D1 (+143%, P < 0.01), a return to baseline at Post, and a decrease at Post + 1 (-56%, P < 0.05). CONCLUSIONS: These data provide evidence that 2 h of moderate daily exercise training can attenuate the oxidative stress induced by continuous hypoxic exposure.
|
|
| 20. |
- Debevec, T, et al.
(författare)
-
Normoxic and hypoxic performance following four weeks of normobaric hypoxic training
- 2010
-
Ingår i: Aviation, Space and Environmental Medicine. - : Aerospace Medical Association. - 0095-6562 .- 1943-4448. ; 81:4, s. 387-393
-
Tidskriftsartikel (refereegranskat)abstract
- INTRODUCTION:Although training in hypoxia has been suggested to improve sea level and altitude performance, most studies have only evaluated its effect on maximal aerobic capacity in either normoxia or hypoxia. The present study evaluated the effect of a live low-train high training regimen on both normoxic and hypoxic endurance performance and aerobic capacity.METHODS:There were 18 male subjects who performed 20 training sessions in either a normoxic (F(IO2) = 0.21) or hypoxic (F(IO2) = 0.12) environment. Both the Control (N = 9) and Hypoxic (N = 9) group subjects trained at an intensity that maintained their heart rate at a level corresponding to that elicited at 50% of peak power output attained in normoxia or hypoxia, respectively. Before, during, upon completion, and 10 d after the protocol, subjects' aerobic capacity (VO2 peak) and endurance performance (80% of VO2 peak) were determined under normoxic and hypoxic conditions.RESULTS:Mean +/- SD normoxic VO2 peak increased significantly only in the Control group from 45.7 +/- 6.1 to 53.9 +/- 3.9 (ml x kg(-1) x min(-1)), whereas hypoxic VO2 peak did not improve in either group. The Control group exhibited significant improvements in normoxic, but not hypoxic peak power output (PPO) and time to exhaustion, whereas the Hypoxic group only exhibited improvements in normoxic time to exhaustion. During each testing period, we also assessed pulmonary function, selected hematological variables, and anthropometry. There were no significant changes in these variables in either group after the training protocol.CONCLUSION:The hypoxic training regimen used in the present study had no significant effect on altitude and sea level performance.
|
|
| 21. |
|
|
| 22. |
|
|
| 23. |
|
|
| 24. |
|
|
| 25. |
- Keramidas, Michail E., et al.
(författare)
-
Respiratory muscle endurance training : Effect on normoxic and hypoxic exercise performance
- 2010
-
Ingår i: European Journal of Applied Physiology. - : Springer Science and Business Media LLC. - 1439-6319 .- 1439-6327. ; 108:4, s. 759-769
-
Tidskriftsartikel (refereegranskat)abstract
- The aim of this study was to investigate the effect of respiratory muscle endurance training on endurance exercise performance in normoxic and hypoxic conditions. Eighteen healthy males were stratified for age and aerobic capacity; and randomly assigned either to the respiratory muscle endurance training (RMT = 9) or to the control training group (CON = 9). Both groups trained on a cycle-ergometer 1 h day(-1), 5 days per week for a period of 4 weeks at an intensity corresponding to 50% of peak power output. Additionally, the RMT group performed a 30-min specific endurance training of respiratory muscles (isocapnic hyperpnea) prior to the cycle ergometry. Pre, Mid, Post and 10 days after the end of training period, subjects conducted pulmonary function tests (PFTs), maximal aerobic tests in normoxia ((V) over dotO(2max)NOR), and in hypoxia ((V) over dotO(2max)HYPO; F(I)O(2) = 0.12); and constant-load tests at 80% of (V) over dotO(2max)NOR in normoxia (CLT(NOR)), and in hypoxia (CLT(HYPO)). Both groups enhanced (V) over dotO(2max)NOR (CON: +13.5%; RMT: +13.4%), but only the RMT group improved (V) over dotO(2max)HYPO Post training (CON: -6.5%; RMT: +14.2%). Post training, the CON group increased peak power output, whereas the RMT group had higher values of maximum ventilation. Both groups increased CLT(NOR) duration (CON: +79.9%; RMT: +116.6%), but only the RMT group maintained a significantly higher CLT(NOR) 10 days after training (CON: +56.7%; RMT: +91.3%). CLT(HYPO) remained unchanged in both groups. Therefore, the respiratory muscle endurance training combined with cycle ergometer training enhanced aerobic capacity in hypoxia above the control values, but did not in normoxia. Moreover, no additional effect was obtained during constant-load exercise.
|
|
