Chapter title |
The Spatial Distribution of Absolute Skeletal Muscle Deoxygenation During Ramp-Incremental Exercise Is Not Influenced by Hypoxia.
|
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Chapter number | 2 |
Book title |
Oxygen Transport to Tissue XXXVII
|
Published in |
Advances in experimental medicine and biology, January 2016
|
DOI | 10.1007/978-1-4939-3023-4_2 |
Pubmed ID | |
Book ISBNs |
978-1-4939-3022-7, 978-1-4939-3023-4
|
Authors |
Bowen, T Scott, Koga, Shunsaku, Amano, Tatsuro, Kondo, Narihiko, Rossiter, Harry B, T. Scott Bowen, Shunsaku Koga, Tatsuro Amano, Narihiko Kondo, Harry B. Rossiter |
Editors |
Clare E. Elwell, Terence S. Leung, David K. Harrison |
Abstract |
Time-resolved near-infrared spectroscopy (TRS-NIRS) allows absolute quantitation of deoxygenated haemoglobin and myoglobin concentration ([HHb]) in skeletal muscle. We recently showed that the spatial distribution of peak [HHb] within the quadriceps during moderate-intensity cycling is reduced with progressive hypoxia and this is associated with impaired aerobic energy provision. We therefore aimed to determine whether reduced spatial distribution of skeletal muscle [HHb] was associated with impaired aerobic energy transfer during exhaustive ramp-incremental exercise in hypoxia. Seven healthy men performed ramp-incremental cycle exercise (20 W/min) to exhaustion at 3 fractional inspired O2 concentrations (FIO2): 0.21, 0.16, 0.12. Pulmonary O2 uptake ([Formula: see text]) was measured using a flow meter and gas analyser system. Lactate threshold (LT) was estimated non-invasively. Absolute muscle deoxygenation was quantified by multichannel TRS-NIRS from the rectus femoris and vastus lateralis (proximal and distal regions). [Formula: see text] and LT were progressively reduced (p < 0.05) with hypoxia. There was a significant effect (p < 0.05) of FIO2 on [HHb] at baseline, LT, and peak. However the spatial variance of [HHb] was not different between FIO2 conditions. Peak total Hb ([Hbtot]) was significantly reduced between FIO2 conditions (p < 0.001). There was no association between reductions in the spatial distribution of skeletal muscle [HHb] and indices of aerobic energy transfer during ramp-incremental exercise in hypoxia. While regional [HHb] quantified by TRS-NIRS at exhaustion was greater in hypoxia, the spatial distribution of [HHb] was unaffected. Interestingly, peak [Hbtot] was reduced at the tolerable limit in hypoxia implying a vasodilatory reserve may exist in conditions with reduced FIO2. |
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