J Koschate1, L Thieschäfer2, U Drescher2, U Hoffmann2. 1. Institute of Physiology and Anatomy, German Sport University Cologne, Am Sportpark Muengersdorf 6, 50933, Cologne, Germany. J.Koschate@dshs-koeln.de. 2. Institute of Physiology and Anatomy, German Sport University Cologne, Am Sportpark Muengersdorf 6, 50933, Cologne, Germany.
Abstract
PURPOSE: The effects of 60 days of head down tilt bed rest (HDBR) with and without the application of a reactive jump countermeasure were investigated, using a method which enables to discriminate between pulmonary ([Formula: see text]O2pulm) and muscular ([Formula: see text]O2musc) oxygen uptake kinetics to control for hemodynamic influences. METHODS:22 subjects were randomly allocated to either a group performing a reactive jumps countermeasure (JUMP; n = 11, male, 29 ± 7 years, 23.9 ± 1.3 kg m- 2) or a control group (CTRL; n = 11, male, 29 ± 6 years, 23.3 ± 2.0 kg m- 2). Heart rate (HR) and [Formula: see text]O2pulm were measured in response to repeated changes in work rate between 30 and 80 W before (BDC-9) and two times after HDBR (R+ 2, R+ 13). Kinetic responses of HR, [Formula: see text]O2pulm, and [Formula: see text]O2musc were assessed applying time series analysis. Higher maxima in cross-correlation functions (CCFmax(x)) between work rate and the respective parameter indicate faster kinetics responses. Statistical analysis was performed applying multifactorial analysis of variance. RESULTS:CCFmax([Formula: see text]O2musc) and CCFmax([Formula: see text]O2pulm) were not significantly different before and after HDBR (P > 0.05). CCFmax(HR) decreased following bed rest (JUMP: BDC-9: 0.30 ± 0.09 vs. R+ 2: 0.28 ± 0.06 vs. R+13: 0.28 ± 0.07; CTRL: 0.35 ± 0.09 vs. 0.27 ± 0.06 vs. 0.33 ± 0.07 P = 0.025). No significant differences between the groups were observed (P > 0.05). Significant alterations were found for CCFmax of mean arterial blood pressure (mBP) after HDBR (JUMP: BDC-9: 0.21 ± 0.07 vs. R+ 2: 0.30 ± 0.13 vs. R+ 13: 0.28 ± 0.08; CTRL: 0.25 ± 0.07 vs. 0.38 ± 0.13 vs. 0.28 ± 0.08; P = 0.008). CONCLUSIONS: Despite hemodynamic changes, [Formula: see text]O2 kinetics seem to be preserved for a longer period of HDBR, even without the application of a countermeasure.
RCT Entities:
PURPOSE: The effects of 60 days of head down tilt bed rest (HDBR) with and without the application of a reactive jump countermeasure were investigated, using a method which enables to discriminate between pulmonary ([Formula: see text]O2pulm) and muscular ([Formula: see text]O2musc) oxygen uptake kinetics to control for hemodynamic influences. METHODS: 22 subjects were randomly allocated to either a group performing a reactive jumps countermeasure (JUMP; n = 11, male, 29 ± 7 years, 23.9 ± 1.3 kg m- 2) or a control group (CTRL; n = 11, male, 29 ± 6 years, 23.3 ± 2.0 kg m- 2). Heart rate (HR) and [Formula: see text]O2pulm were measured in response to repeated changes in work rate between 30 and 80 W before (BDC-9) and two times after HDBR (R+ 2, R+ 13). Kinetic responses of HR, [Formula: see text]O2pulm, and [Formula: see text]O2musc were assessed applying time series analysis. Higher maxima in cross-correlation functions (CCFmax(x)) between work rate and the respective parameter indicate faster kinetics responses. Statistical analysis was performed applying multifactorial analysis of variance. RESULTS: CCFmax([Formula: see text]O2musc) and CCFmax([Formula: see text]O2pulm) were not significantly different before and after HDBR (P > 0.05). CCFmax(HR) decreased following bed rest (JUMP: BDC-9: 0.30 ± 0.09 vs. R+ 2: 0.28 ± 0.06 vs. R+13: 0.28 ± 0.07; CTRL: 0.35 ± 0.09 vs. 0.27 ± 0.06 vs. 0.33 ± 0.07 P = 0.025). No significant differences between the groups were observed (P > 0.05). Significant alterations were found for CCFmax of mean arterial blood pressure (mBP) after HDBR (JUMP: BDC-9: 0.21 ± 0.07 vs. R+ 2: 0.30 ± 0.13 vs. R+ 13: 0.28 ± 0.08; CTRL: 0.25 ± 0.07 vs. 0.38 ± 0.13 vs. 0.28 ± 0.08; P = 0.008). CONCLUSIONS: Despite hemodynamic changes, [Formula: see text]O2 kinetics seem to be preserved for a longer period of HDBR, even without the application of a countermeasure.
Authors: Juan M Murias; Matthew D Spencer; John M Kowalchuk; Donald H Paterson Journal: Am J Physiol Regul Integr Comp Physiol Date: 2011-04-13 Impact factor: 3.619
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