College of Engineering, Swansea Univ., Singleton Park, Swansea, SA2 8PP, UK.
Am J Physiol Regul Integr Comp Physiol. 2012 Oct 15;303(8):R791-8. doi: 10.1152/ajpregu.00203.2012. Epub 2012 Aug 1.
It is unclear whether pulmonary oxygen uptake (Vo2) kinetics demonstrate linear, first-order behavior during supra gas exchange threshold exercise. Resolution of this issue is pertinent to the elucidation of the factors regulating oxygen uptake (Vo2) kinetics, with oxygen availability and utilization proposed as putative mediators. To reexamine this issue with the advantage of a relatively large sample size, 50 young (24 ± 4 yr) and 15 late middle-aged (54 ± 3 yr) participants completed repeated bouts of moderate and heavy exercise. Pulmonary gas exchange, heart rate (HR), and cardiac output (Q) variables were measured throughout. The phase II τ was slower during heavy exercise in both young (moderate: 22 ± 9; heavy: 29 ± 9 s; P ≤ 0.001) and middle-aged (moderate: 22 ± 9; heavy: 30 ± 8 s; P ≤ 0.001) individuals. The HR τ was slower during heavy exercise in young (moderate: 33 ± 10; heavy: 44 ± 15 s; P ≤ 0.05) and middle-aged (moderate: 30 ± 12; heavy: 50 ± 20 s; P ≤ 0.05) participants, and the Q τ showed a similar trend (young moderate: 21 ± 13; heavy: 28 ± 16 s; middle-aged moderate: 32 ± 13; heavy: 40 ± 15 s; P ≥ 0.05). There were no differences in primary component Vo2 kinetics between age groups, but the middle-aged group had a significantly reduced Vo2 slow component amplitude in both absolute (young: 0.25 ± 0.09; middle-aged: 0.11 ± 0.06 l/min; P ≤ 0.05) and relative terms (young: 15 ± 10; middle-aged: 9 ± 4%; P ≤ 0.05). Thus Vo2 kinetics do not demonstrate dynamic linearity during heavy intensity exercise. Speculatively, the slower phase II τ during heavy exercise might be attributable to reduced oxygen availability. Finally, the primary and slow components of Vo2 kinetics appear to be differentially influenced by middle age.
在超过气体交换阈值的运动中，肺氧摄取（Vo2）动力学是否表现出线性、一级行为尚不清楚。解决这个问题对于阐明调节氧摄取（Vo2）动力学的因素至关重要，氧气可用性和利用率被认为是潜在的介质。为了利用相对较大的样本量重新检查这个问题，50 名年轻（24 ± 4 岁）和 15 名中老年（54 ± 3 岁）参与者完成了多次中等强度和高强度运动。整个过程中测量了肺气体交换、心率（HR）和心输出量（Q）变量。在年轻人（中等强度：22 ± 9；高强度：29 ± 9 秒；P ≤ 0.001）和中老年人（中等强度：22 ± 9；高强度：29 ± 9 秒；P ≤ 0.001）中，高强度运动时的第二相 τ 较慢。在年轻人（中等强度：33 ± 10；高强度：44 ± 15 秒；P ≤ 0.05）和中老年人（中等强度：30 ± 12；高强度：50 ± 20 秒；P ≤ 0.05）中，高强度运动时的 HR τ 较慢，Q τ 也呈现出类似的趋势（年轻的中等强度：21 ± 13；高强度：28 ± 16 秒；中年的中等强度：32 ± 13；高强度：40 ± 15 秒；P ≥ 0.05）。两组年龄组之间的主要成分 Vo2 动力学没有差异，但在绝对值（年轻人：0.25 ± 0.09；中年人：0.11 ± 0.06 l/min；P ≤ 0.05）和相对值（年轻人：15 ± 10；中年人：9 ± 4%；P ≤ 0.05）方面，中年组的 Vo2 慢成分幅度明显降低。因此，Vo2 动力学在高强度运动中并不表现出动态线性。推测，高强度运动时第二相 τ 较慢可能是由于氧气可用性降低所致。最后，Vo2 动力学的主要成分和慢成分似乎受到中年的不同影响。
