Minson C T, Kenney W L
Noll Physiological Research Center, Penn State University, University Park, PA 16802-6900, USA.
Med Sci Sports Exerc. 1997 Jan;29(1):75-81. doi: 10.1097/00005768-199701000-00011.
To determine whether chronological age, independent of changes in aerobic capacity, alters cardiac output (Qc), the central hemodynamic responses to intermittent incremental cycle exercise were studied in two groups of men. Qc was measured at rest and during exercise at 35%, 60%, 75%, and 85% peak aerobic capacity (VO2peak) using a CO2 rebreathing method in seven trained older (65 +/- 2 yr) and eight normally active but untrained young men (26 +/- 1 yr) matched for VO2peak and anthropometric measures. Subjects were tested in both a thermoneutral (22 degrees C) and a warm (36 degrees C) environment to investigate possible differential cardiovascular responses to exercise in the heat. Only subjects with no history of pulmonary, cardiac, neuromuscular, or endocrine disease and a normal electrocardiogram were studied. The older men had significantly lower (P < 0.05) Qc relative to the younger men at intensities greater than 60% VO2peak in both environmental conditions. At these higher intensities, the older men had a significantly higher stroke volume (SV) and lower heart rate (HR) (P < 0.05). A higher arteriovenous oxygen difference ((a-v)O2)) compared with their younger counterparts enabled the older men to exercise at the same absolute intensity, most likely because of training induced changes in left-ventricular performance and oxygen extraction. The addition of an exogenous heat source did not alter the Qc response in either group of men; however, a higher HR (P < 0.05) and smaller SV (P > 0.05) were observed in the young men during exercise in the heat. This may reflect previously reported differences in the skin blood flow response of VO2peak-matched young and older men during exercise. It is suggested that endurance trained older men can enhance left-ventricular performance to augment SV, but not sufficiently to maintain Qc in light of an attenuated HR response during exercise at intensities above 60% VO2peak.
为了确定不依赖有氧能力变化的实际年龄是否会改变心输出量（Qc），对两组男性进行了间歇性递增循环运动的中心血流动力学反应研究。在7名训练有素的老年男性（65±2岁）和8名正常活动但未受过训练的年轻男性（26±1岁）中，使用二氧化碳重呼吸法在静息状态以及运动至35%、60%、75%和85%峰值有氧能力（VO2peak）时测量Qc，两组男性的VO2peak和人体测量指标相匹配。在热中性（22摄氏度）和温暖（36摄氏度）环境中对受试者进行测试，以研究热环境下运动时可能存在的不同心血管反应。仅研究无肺部、心脏、神经肌肉或内分泌疾病史且心电图正常的受试者。在两种环境条件下，当运动强度大于60%VO2peak时，老年男性的Qc相对于年轻男性显著降低（P<0.05）。在这些较高强度下，老年男性的每搏输出量（SV）显著更高，心率（HR）更低（P<0.05）。与年轻男性相比，老年男性更高的动静脉氧差（(a-v)O2）使他们能够在相同的绝对强度下运动，这很可能是由于训练引起的左心室功能和氧摄取变化。添加外源热源并未改变两组男性的Qc反应；然而，在热环境中运动时，年轻男性的HR更高（P<0.05），SV更小（P>0.05）。这可能反映了先前报道的VO2peak匹配的年轻和老年男性在运动时皮肤血流反应的差异。研究表明，耐力训练的老年男性可以增强左心室功能以增加SV，但在运动强度高于60%VO2peak时，由于HR反应减弱，不足以维持Qc。
