TY - JOUR
T1 - Influence of exercise intensity on skeletal muscle blood flow, O2 extraction and O2 uptake on-kinetics
AU - Jones, Andrew M
AU - Krustrup, Peter
AU - Wilkerson, Daryl P
AU - Berger, Nicolas J
AU - Calbet, José A
AU - Bangsbo, Jens
N1 - CURIS 2012 5200 118
PY - 2012/9
Y1 - 2012/9
N2 - Following the start of low-intensity exercise in healthy humans, it has been established that the kinetics of skeletal muscle O2 delivery is faster than, and does not limit, the kinetics of muscle O2 uptake. Direct data are lacking, however, on the question of whether O2 delivery might limit kinetics during high-intensity exercise. Using multiple exercise transitions to enhance confidence in parameter estimation, we therefore investigated the kinetics of, and inter-relationships between, muscle blood flow, a- difference and following the onset of low-intensity (LI) and high-intensity (HI) exercise. Seven healthy males completed four 6 min bouts of LI and four 6 min bouts of HI single-legged knee-extension exercise. Blood was frequently drawn from the femoral artery and vein during exercise and, a- difference and were calculated and subsequently modelled using non-linear regression techniques. For LI, the fundamental component mean response time (MRTp) for kinetics was significantly shorter than kinetics (mean ± SEM, 18 ± 4 vs. 30 ± 4 s; P < 0.05), whereas for HI, the MRTp for and was not significantly different (27 ± 5 vs. 29 ± 4 s, respectively). There was no difference in the MRTp for either or between the two exercise intensities; however, the MRTp for a- difference was significantly shorter for HI compared with LI (17 ± 3 vs. 28 ± 4 s; P < 0.05). Excess O2, i.e. oxygen not taken up (×), was significantly elevated within the first 5 s of exercise and remained unaltered thereafter, with no differences between LI and HI. These results indicate that bulk O2 delivery does not limit kinetics following the onset of LI or HI knee-extension exercise.
AB - Following the start of low-intensity exercise in healthy humans, it has been established that the kinetics of skeletal muscle O2 delivery is faster than, and does not limit, the kinetics of muscle O2 uptake. Direct data are lacking, however, on the question of whether O2 delivery might limit kinetics during high-intensity exercise. Using multiple exercise transitions to enhance confidence in parameter estimation, we therefore investigated the kinetics of, and inter-relationships between, muscle blood flow, a- difference and following the onset of low-intensity (LI) and high-intensity (HI) exercise. Seven healthy males completed four 6 min bouts of LI and four 6 min bouts of HI single-legged knee-extension exercise. Blood was frequently drawn from the femoral artery and vein during exercise and, a- difference and were calculated and subsequently modelled using non-linear regression techniques. For LI, the fundamental component mean response time (MRTp) for kinetics was significantly shorter than kinetics (mean ± SEM, 18 ± 4 vs. 30 ± 4 s; P < 0.05), whereas for HI, the MRTp for and was not significantly different (27 ± 5 vs. 29 ± 4 s, respectively). There was no difference in the MRTp for either or between the two exercise intensities; however, the MRTp for a- difference was significantly shorter for HI compared with LI (17 ± 3 vs. 28 ± 4 s; P < 0.05). Excess O2, i.e. oxygen not taken up (×), was significantly elevated within the first 5 s of exercise and remained unaltered thereafter, with no differences between LI and HI. These results indicate that bulk O2 delivery does not limit kinetics following the onset of LI or HI knee-extension exercise.
U2 - 10.1113/jphysiol.2012.233064
DO - 10.1113/jphysiol.2012.233064
M3 - Journal article
C2 - 22711961
SN - 0022-3751
VL - 590
SP - 4363
EP - 4376
JO - The Journal of Physiology
JF - The Journal of Physiology
IS - 17
ER -