Determinants of oxygen uptake kinetics in older humans following single-limb endurance exercise training.
We hypothesised that the observed acceleration in the kinetics of exercise on-transient oxygen uptake (VO2) of five older humans (77 +/- 7 years (mean +/- S.D.) following 9 weeks of single-leg endurance exercise training was due to adaptations at the level of the muscle cell. Prior to, and following training, subjects performed constant-load single-limb knee extension exercise. Following training VO2 kinetics (phase 2, tau) were accelerated in the trained leg (week 0, 92 +/- 44 s; week 9, 48 +/- 22 s) and unchanged in the untrained leg (week 0, 104 +/- 43 s; week 9, 126 +/- 35 s). The kinetics of mean blood velocity in the femoral artery were faster than the kinetics of VO2, but were unchanged in both the trained (week 0, 19 +/- 10 s; week 9, 26 +/- 11 s) and untrained leg (week 0, 20 +/- 18 s; week 9, 18 +/- 10 s). Maximal citrate synthase activity, measured from biopsies of the vastus lateralis muscle, increased (P < 0.05) in the trained leg (week 0, 6.7 +/- 2.0 micromol x (g wet wt)(-1) x min(-1); week 9, 11.4 +/- 3.6 micromol x (g wet wt)(-1) x min(-1)) but was unchanged in the untrained leg (week 0, 5.9 +/- 0.5 micromol x (g wet wt)(-1) x min(-1); week 9, 7.9 +/- 1.9 micromol x (g wet wt)(-1) x min(-1)). These data suggest that the acceleration of VO2 kinetics was due to an improved rate of O2 utilisation by the muscle, but was not a result of increased O2 delivery.
Bell
C
C
Centre For Activity and Ageing, School of Kinesiology, The University of Western Ontario, London, Ontario, Canada N6A 3K7.
Paterson
D H
DH
Kowalchuk
J M
JM
Moy
A P
AP
Thorp
D B
DB
Noble
E G
EG
Taylor
A W
AW
Cunningham
D A
DA
D000368:Aged; D000369:Aged, 80 and over; D001783:Blood Flow Velocity; D002950:Citrate (si)-Synthase / Q000378:metabolism; D005263:Femoral Artery / Q000000981:diagnostic imaging / Q000502:physiology*; D006801:Humans; D007700:Kinetics; D007866:Leg / Q000098:blood supply / Q000502:physiology; D008297:Male; D018482:Muscle, Skeletal / Q000098:blood supply / Q000201:enzymology; D010101:Oxygen Consumption; D010807:Physical Endurance / Q000502:physiology*; D012039:Regional Blood Flow / Q000502:physiology; D018617:Ultrasonography, Doppler, Pulsed
D002950:Citrate (si)-Synthase