1. Maintained peak leg and pulmonary VO2 despite substantial reduction in muscle mitochondrial capacity.
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Boushel, R., Gnaiger, E., Larsen, F. J., Helge, J. W., González‐Alonso, J., Ara, I., Munch‐Andersen, T., Hall, G., Søndergaard, H., Saltin, B., and Calbet, J. A. L.
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SKELETAL muscle physiology , *ACTIVE oxygen in the body , *ANALYSIS of variance , *BIOPSY , *BLOOD circulation , *EXERCISE physiology , *HEMATOCRIT , *HEMOGLOBINS , *LACTATES , *LEG , *LONGITUDINAL method , *SKIING , *MITOCHONDRIA , *PROBABILITY theory , *PULMONARY gas exchange , *RESEARCH funding , *T-test (Statistics) , *REPEATED measures design , *OXYGEN consumption , *EXERCISE intensity , *SKELETAL muscle , *DESCRIPTIVE statistics - Abstract
We recently reported the circulatory and muscle oxidative capacities of the arm after prolonged low-intensity skiing in the arctic ( Boushel et al., 2014). In the present study, leg VO2 was measured by the Fick method during leg cycling while muscle mitochondrial capacity was examined on a biopsy of the vastus lateralis in healthy volunteers (7 male, 2 female) before and after 42 days of skiing at 60% HR max. Peak pulmonary VO2 (3.52 ± 0.18 L.min−1 pre vs 3.52 ± 0.19 post) and VO2 across the leg (2.8 ± 0.4L.min−1 pre vs 3.0 ± 0.2 post) were unchanged after the ski journey. Peak leg O2 delivery (3.6 ± 0.2 L.min−1 pre vs 3.8 ± 0.4 post), O2 extraction (82 ± 1% pre vs 83 ± 1 post), and muscle capillaries per mm2 (576 ± 17 pre vs 612 ± 28 post) were also unchanged; however, leg muscle mitochondrial OXPHOS capacity was reduced (90 ± 3 pmol.sec−1.mg−1 pre vs 70 ± 2 post, P < 0.05) as was citrate synthase activity (40 ± 3 μmol.min−1.g−1 pre vs 34 ± 3 vs P < 0.05). These findings indicate that peak muscle VO2 can be sustained with a substantial reduction in mitochondrial OXPHOS capacity. This is achieved at a similar O2 delivery and a higher relative ADP-stimulated mitochondrial respiration at a higher mitochondrial p50. These findings support the concept that muscle mitochondrial respiration is submaximal at VO2max, and that mitochondrial volume can be downregulated by chronic energy demand. [ABSTRACT FROM AUTHOR]
- Published
- 2015
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