Discrepancy between femoral and capillary blood flow kinetics during knee extension exercise

作者：Schlup S J; Ade C J; Broxterman R M; Barstow T J^*

来源：Respiratory Physiology & Neurobiology, 2015, 219: 69-77.

DOI：10.1016/j.resp.2015.08.005

• Blood flow
• Exercise
• Kinetics

Capillary blood flow (Q(CAP)) kinetics have previously been shown to be significantly slower than femoral artery (Q(FA)) kinetics following the onset of dynamic knee extension exercise. If the increase in Quip does not follow a similar time course to Q(FA), then a substantial proportion of the available blood flow is not distributed to the working muscle. One possible explanation for this discrepancy is that blood flow also increases to the nonworking lower leg muscles. Therefore, the present study aimed to determine if a reduction in lower limb blood flow, via arterial occlusion below the knee, alters the kinetics of Q(FA) and Q(CAP), during knee extension exercise, and thus provide insight into the potential mechanisms controlling the rapid increase in Q(FA). Subjects performed a ramp max test to determine the work rate at which gas exchange threshold (GET) occurred. At least four constant work rate trials with and without below-knee occlusion were conducted at work rates eliciting similar to 80% GET. Pulmonary gas exchange, near-infrared spectroscopy and Q(FA) measurements were taken continuously during each exercise bout. Muscle oxygen uptake (VO(2)m) and deoxy[hemoglobin myoglobin] were used to estimate Q(CAP). There was no significant difference between the uncuffed and cuffed conditions in any response (P > 0.05). The mean response times (MRT) of Q(FA) were 18.7 +/- 14.2 s (uncuffed) and 24.6 +/- 14.9 s (cuffed). Q(CAP) MRTs were 51.8 +/- 23.4 s (uncuffed) and 56.7 +/- 23.2 s (cuffed), which were not significantly different from the time constants (tau) of VO(2)m (39.7 +/- 23.2 s (uncuffed) and 46.3 +/- 24.1 s (cuffed). However, the MRT of Q(FA) was significantly faster (P<0.05) than the MRT of Q(CAP) and tau VO(2)m, tau VO(2)m and MRT Q(CAP) were significantly correlated and estimated Q(CAP) kinetics tracked VO(2)m following exercise onset. Cuffing below the knee did not significantly change the kinetics of Q(FA), Q(CAP) or VO(2)m, although an effect size of 1.02 suggested that a significant effect on Q(FA) may have been hidden by small subject number.

• 出版日期2015-12