Jacobs 2012 J Appl Physiol

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Jacobs R, Lundby C (2012) Mitochondria express enhanced quality as well as quantity in association with aerobic fitness across recreationally active individuals up to elite athletes. J Appl Physiol 114:344-50.

» PMID: 23221957

Jacobs R, Lundby C (2012) J Appl Physiol

Abstract: Changes in skeletal muscle respiratory capacity parallel that of aerobic fitness. It is unknown whether mitochondrial content, alone, can fully account for these differences in skeletal muscle respiratory capacity. The aim of the present study was to examine quantitative and qualitative mitochondrial characteristics across four different groups (n = 6 each), separated by cardiorespiratory fitness. High-resolution respirometry was performed on muscle samples to compare respiratory capacity and efficiency in active (AT), well-trained (WT), highly-trained (HT), and elite (ET) individuals. Maximal exercise capacity (VO2max; ml O2 min-1 kg-1) differed across all groups with mean ± SD values of 51 ± 4, 64 ± 5, 71 ± 2, and 77 ± 3, respectively. Mitochondrial content assessed by citrate synthase activity was higher in ET compared to AT and WT (29 ± 7 versus 16 ± 4 and 19 ± 4 and nmol min-1 mg ww-1, respectively). When normalizing respiration to mitochondrial content, the respiratory capacities during maximal fatty acid oxidation (p = 0.003), maximal state 3 respiration (p = 0.021), and total electron transport system capacity (p = 0.008) improved in respect to VO2max. The coupling efficiency of β-oxidation, however, expressed no difference across groups. These data demonstrate the quantitative and qualitative differences that exist in skeletal muscle mitochondrial respiratory capacity and efficiency across individuals that differ in aerobic capacity. Mitochondrial-specific respiration capacities during β-oxidation, maximal oxidative phosphorylation, and electron transport system capacity all correspondingly improve with aerobic capacity, independent of mitochondrial content in human skeletal muscle. Keywords: Aerobic fitness

O2k-Network Lab: CH Zurich Lundby C, US CO Colorado Springs Jacobs RA


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Organism: Human  Tissue;cell: Skeletal muscle  Preparation: Permeabilized tissue 

Regulation: Coupling efficiency;uncoupling, Fatty acid  Coupling state: OXPHOS, ET 

HRR: Oxygraph-2k