B. Walsh et al., Effect of endurance training on oxidative and antioxidative function in human permeabilized muscle fibres, PFLUG ARCH, 442(3), 2001, pp. 420-425
The adaptation of muscle oxidative function to 6 weeks of endurance cycle t
raining was investigated in eight untrained subjects. Peak oxygen consumpti
on ((V) over dot O-2peak) increased by 24% (2.69 +/-0.21 versus 3.34 +/-0.3
0 l O-2 min(-1), mean +/- SEM, P <0.01) and lactate threshold intensity inc
reased by 53% (121 +/- 13 versus 185 +/- 15 W, P<0.01) following the traini
ng period. Muscle biopsy samples were taken from vastus lateralis before an
d after training, and respiration in permeabilized muscle fibres was measur
ed. Following training, non-ADP-stimulated respiration ((V)over dot(O)) of
skinned fibres increased by 35% (0.17<plus/minus>0.01 versus 0.23 +/-0.01 m
mol O-2. min(-1). kg(-1) wet weight, P <0.05) and maximal ADP-stimulated re
spiration ((V) over dot(max)) increased by 38% (1.17 +/-0.07 versus 1.62 +/
-0.14 mmol O-2. min(-1). kg(-1) wet weight, P<0.05). ADP sensitivity [i.e.
the ratio between mitochondrial respiration (after correction for (V) over
dot(O)) at 0.1 mM ADP and (V) over dot(max)] was reduced after training (0.
40<plus/minus>0.05 versus 0.26 +/-0.02; P<0.05). Mitochondrial resistance t
o oxidative stress was investigated by exposing skinned fibres to exogenous
reactive oxygen species (ROS). ADP-stimulated respiration was reduced afte
r ROS exposure and the relative decrease was similar before and after train
ing. It is concluded that after endurance training: (1) the relative increa
se in maximal muscle fibre respiration exceeds that of whole-body oxygen up
take: (2) the sensitivity of mitochondrial respiration to ADP decreases; an
d (3) the impairment of oxidative function in skinned muscle fibres by ROS
remains unchanged.