Effect of endurance training on oxidative and antioxidative function in human permeabilized muscle fibres.
The adaptation of muscle oxidative function to 6 weeks of endurance cycle training was investigated in eight untrained subjects. Peak oxygen consumption (VO2peak) increased by 24% (2.69+/-0.21 versus 3.34+/-0.30 l O2 min(-1), mean +/-SEM, P<0.01) and lactate threshold intensity increased by 53% (121+/-13 versus 185+/-15 W, P<0.01) following the training period. Muscle biopsy samples were taken from vastus lateralis before and after training, and respiration in permeabilized muscle fibres was measured. Following training, non-ADP-stimulated respiration (VO) of skinned fibres increased by 35% (0.17+/-0.01 versus 0.23+/-0.01 mmol O2.min(-1).kg(-1) wet weight, P<0.05) and maximal ADP-stimulated respiration (VmaX) increased by 38% (1.17+/-0.07 versus 1.62+/-0.14 mmol O2.min(-1).kg(-1) wet weight, P<0.05). ADP sensitivity [i.e. the ratio between mitochondrial respiration (after correction for VO) at 0.1 mM ADP and Vmax] was reduced after training (0.40+/-0.05 versus 0.26+/-0.02; P<0.05). Mitochondrial resistance to oxidative stress was investigated by exposing skinned fibres to exogenous reactive oxygen species (ROS). ADP-stimulated respiration was reduced after ROS exposure and the relative decrease was similar before and after training. It is concluded that after endurance training: (1) the relative increase in maximal muscle fibre respiration exceeds that of whole-body oxygen uptake; (2) the sensitivity of mitochondrial respiration to ADP decreases; and (3) the impairment of oxidative function in skinned muscle fibres by ROS remains unchanged.
Walsh
B
B
Department of Physiology and Pharmacology, Karolinska Institute, Stockholm, Sweden.
Tonkonogi
M
M
Sahlin
K
K
D000328:Adult; D000975:Antioxidants / Q000378:metabolism*; D019069:Cell Respiration / Q000502:physiology; D005260:Female; D005609:Free Radicals / Q000378:metabolism; D006801:Humans; D066298:In Vitro Techniques; D008297:Male; D008928:Mitochondria / Q000378:metabolism; D018485:Muscle Fibers, Skeletal / Q000378:metabolism*; D018482:Muscle, Skeletal / Q000166:cytology / Q000378:metabolism*; D010085:Oxidative Phosphorylation; D010101:Oxygen Consumption / Q000502:physiology; D010807:Physical Endurance / Q000502:physiology*; D017382:Reactive Oxygen Species / Q000378:metabolism
D000975:Antioxidants; D005609:Free Radicals; D017382:Reactive Oxygen Species