| 1. |
- Keramidas, Michail E., et al.
(författare)
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Acute normobaric hyperoxia transiently attenuates plasma erythropoietin concentration in healthy males : evidence against the 'normobaric oxygen paradox' theory
- 2011
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Ingår i: Acta Physiologica. - : Wiley-Blackwell. - 1748-1708 .- 1748-1716. ; 202:1, s. 91-98
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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.
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| 2. |
- Keramidas, Michail E., et al.
(författare)
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Enhancement of the finger cold-induced vasodilation response with exercise training
- 2010
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Ingår i: European Journal of Applied Physiology. - : Springer Science and Business Media LLC. - 1439-6319 .- 1439-6327. ; 109:1, s. 133-140
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Tidskriftsartikel (refereegranskat)abstract
- Cold-induced vasodilatation (CIVD) is a cyclical increase in finger temperature that has been suggested to provide cryoprotective function during cold exposures. Physical fitness has been suggested as a potential factor that could affect CIVD response, possibly via central (increased cardiac output, decreased sympathetic nerve activity) and/or peripheral (increased microcirculation) cardiovascular and neural adaptations to exercise training. Therefore, the purpose of this study was to investigate the effect of endurance exercise training on the CIVD response. Eighteen healthy males trained 1 h d(-1) on a cycle ergometer at 50% of peak power output, 5 days week(-1) for 4-weeks. Pre, Mid, Post, and 10 days after the cessation of training and on separate days, subjects performed an incremental exercise test to exhaustion ((V) over dotO(2peak)); and a 30-min hand immersion in 8 degrees C water to examine their CIVD response. The exercise-training regimen significantly increased (V) over dotO(2peak) (Pre: 46.0 +/- 5.9, Mid: 52.5 +/- 5.7, Post: 52.1 +/- 6.2, After: 52.6 +/- 7.6 ml kg(-1) min-1; P < 0.001). There was a significant increase in average finger skin temperature (Pre: 11.9 +/- 2.4, After: 13.5 +/- 2.5 degrees C; P < 0.05), the number of waves (Pre: 1.1 +/- 1.0, After: 1.7 +/- 1.1; P < 0.001) and the thermal sensation (Pre: 1.7 +/- 0.9, After: 2.5 +/- 1.4; P < 0.001), after training. In conclusion, the aforementioned endurance exercise training significantly improved the finger CIVD response during cold-water hand immersion.
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| 3. |
- Keramidas, Michail E., et al.
(författare)
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Respiratory muscle endurance training : Effect on normoxic and hypoxic exercise performance
- 2010
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Ingår i: European Journal of Applied Physiology. - : Springer Science and Business Media LLC. - 1439-6319 .- 1439-6327. ; 108:4, s. 759-769
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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.
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| 4. |
- Mekjavic, I.B., et al.
(författare)
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Hyperbaric oxygen therapy does not affect recovery from delayed onset muscle soreness
- 2000
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Ingår i: Medicine & Science in Sports & Exercise. - : Ovid Technologies (Wolters Kluwer Health). - 0195-9131 .- 1530-0315. ; 32:3, s. 558-563
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Tidskriftsartikel (refereegranskat)abstract
- PURPOSE: This study investigated whether hyperbaric oxygen therapy (HBOT) improves recovery after exercise-induced muscle injury. METHODS: Healthy male subjects (N = 24) were randomly assigned to either a placebo group or a HBOT group. Subjects were tested for maximal isometric strength (preexercise) of their right elbow flexors. Each subject then completed a high-force eccentric workout of the elbow flexor muscle group to induce delayed onset muscle soreness (DOMS). On the seven successive days after this workout, the subjects were exposed to a hyperbaric environment of 2.5 ATA for 60 min, inspiring either a normoxic mixture (P(I)O2 = 0.2 ATA; placebo group) or a hyperoxic gas mixture (P(I)O2 = 2.5 ATA; HBOT group). Before the eccentric workout and daily for the next 10 d, measurements were obtained regarding: maximal isometric muscle strength of the elbow flexor muscles, right upper arm circumferences, and rating of the perceived muscle soreness. RESULTS: Isometric strength decreased significantly from preexercise levels of 25.1 +/- 3.8 kp to postexercise levels of 12.0 +/- 4.6 kp, for the HBOT group, and from 24.6 +/- 3.4 kp to 12.5 +/- 3.7 kp, respectively, for the placebo group. Over the 10-d recovery period, there was no difference in the rate of recovery of muscle strength between the two groups. Perceived soreness peaked at about 48 h after exercise with no difference between groups. Also, the exercise-induced increases in arm circumference were similar in the two groups. CONCLUSIONS: These results indicate that HBOT is not an effective therapy for the treatment of DOMS.
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| 5. |
- McDonnell, A. C., et al.
(författare)
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Effect of hypoxia and bedrest on peripheral vasoconstriction
- 2013
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Ingår i: Proceedings of Life in space for life on earth, 18-22 June 2012, Aberdeen. - : ESA Communications. - 9789290922704 ; , s. 1-2
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Konferensbidrag (refereegranskat)abstract
- Future planetary habitats may expose astronauts to both microgravity and hypobaric hypoxia, both inducing a reduction in peripheral perfusion. Peripheral temperature changes have been linked to sleep onset and quality [5]. However, it is still unknown what effect combining hypoxia and bedrest has on this relationship. Eleven male participants underwent three 10-day campaigns in a randomized manner: 1) normobaric hypoxic ambulatory confinement (HAmb); 2) normobaric hypoxic bed rest (HBR); 3) normobaric normoxic bed rest (NBR). There was no change in skin temperature gradient between the calf and toes, an index of peripheral perfusion (ΔTc-t), over the 10-d period in the HAmb trial. However, there was a significant increase (p< 0.001) in daytime (9am-9pm) ΔTc-t on day 10 of the inactivity/unloading periods (HBR and NBR trials). This reduction in the perfusion of the toes during the daytime was augmented during the HBR trial compared to NBR (p< 0.001). Before and on day 10 of the interventions we conducted polysomnographic assessment, which revealed no changes in sleep onset and/or architecture. These data support the theory that circadian changes in temperature are functionally linked to sleepiness [1].
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| 7. |
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| 8. |
- Amon, M., et al.
(författare)
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The effect of a sleep high-train low regimen on the finger cold-induced vasodilation response
- 2012
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Ingår i: High Altitude Medicine & Biology. - : Mary Ann Liebert Inc. - 1527-0297 .- 1557-8682. ; 13:1, s. 32-39
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Tidskriftsartikel (refereegranskat)abstract
- The present study evaluated the effect of a sleep high-train low regimen on the finger cold-induced vasodilation (CIVD) response. Seventeen healthy males were assigned to either a control (CON; n=9) or experimental (EXP; n=8) group. Each group participated in a 28-day aerobic training program of daily 1-h exercise (50% of peak power output). During the training period, the EXP group slept at a simulated altitude of 2800 meters (week 1) to 3400 m (week 4) above sea level. Normoxic (CIVD(NOR); CON and EXP groups) and hypoxic (CIVD(HYPO); F(I)O(2)=0.12; EXP group only) CIVD characteristics were assessed before and after the training period during a 30-min immersion of the hand in 8°C water. After the intervention, the EXP group had increased average finger skin temperature (CIVD(NOR): +0.5°C; CIVD(HYPO): +0.5°C), number of waves (CIVD(NOR): +0.5; CIVD(HYPO): +0.6), and CIVD amplitude (CIVD(NOR): +1.5°C; CIVD(HYPO): +3°C) in both CIVD tests (p<0.05). In contrast, the CON group had an increase in only the CIVD amplitude (+0.5°C; p<0.05). Thus, the enhancement of aerobic performance combined with altitude acclimatization achieved with the sleep high-train low regimen contributed to an improved finger CIVD response during cold-water hand immersion in both normoxic and hypoxic conditions.
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