McGuire D K, Levine B D, Williamson J W, Snell P G, Blomqvist C G, Saltin B, Mitchell J H
Pauline and Adolph Weinberger Laboratory for Cardiopulmonary Research, University of Texas Southwestern Medical Center, Dallas, TX 75390-9047, USA.
Circulation. 2001 Sep 18;104(12):1350-7.
Cardiovascular capacity declines with aging, as evidenced by declining maximal oxygen uptake (VO(2)max ), with little known about the specific mechanisms of this decline. Our study objective was to assess the effect of a 30-year interval on body composition and cardiovascular response to acute exercise in 5 healthy subjects originally evaluated in 1966.
Anthropometric parameters and the cardiovascular response to acute maximal exercise were assessed with noninvasive techniques. On average, body weight increased 25% (77 versus 100 kg) and percent body fat increased 100% (14% versus 28%), with little change in fat-free mass (66 versus 72 kg). On average, VO(2)max decreased 11% (3.30 versus 2.90 L/min). Likewise, VO(2)max decreased when indexed to total body mass (43 versus 31 mL. kg(-1). min(-1)) or fat-free mass (50 versus 43 mL/kg fat-free mass per minute). Maximal heart rate declined 6% (193 versus 181 bpm) and maximal stroke volume increased 16% (104 versus 121 mL), with no difference observed in maximal cardiac output (20.0 versus 21.4 L/min). Maximal AV oxygen difference declined 15% (16.2 versus 13.8 vol%) and accounted for the entire decrease in cardiovascular capacity.
Cardiovascular capacity declined over the 30-year study interval in these 5 middle-aged men primarily because of an impaired efficiency of maximal peripheral oxygen extraction. Maximal cardiac output was maintained with a decline in maximal heart rate compensated for by an increased maximal stroke volume. Most notably, 3 weeks of bedrest in these same men at 20 years of age (1966) had a more profound impact on physical work capacity than did 3 decades of aging.
心血管能力会随着年龄增长而下降，最大摄氧量（VO₂max）下降就证明了这一点，而关于这种下降的具体机制却知之甚少。我们的研究目的是评估30年的时间间隔对5名最初在1966年接受评估的健康受试者的身体成分以及急性运动时心血管反应的影响。
采用非侵入性技术评估人体测量参数以及急性最大运动时的心血管反应。平均而言，体重增加了25%（从77千克增至100千克），体脂百分比增加了100%（从14%增至28%），去脂体重变化不大（从66千克增至72千克）。平均而言，VO₂max下降了11%（从3.30升/分钟降至2.90升/分钟）。同样，当以总体重为指标时VO₂max也下降了（从43降至31毫升·千克⁻¹·分钟⁻¹），或以去脂体重为指标时VO₂max同样下降了（从50降至43毫升/千克去脂体重每分钟）。最大心率下降了6%（从193次/分钟降至181次/分钟），最大每搏输出量增加了16%（从104毫升增至121毫升），最大心输出量未观察到差异（分别为20.0升/分钟和21.4升/分钟）。最大动静脉氧差下降了15%（从16.2容积%降至13.8容积%），这解释了心血管能力下降的全部原因。
在这30年的研究期间，这5名中年男性的心血管能力下降主要是因为最大外周氧摄取效率受损。最大心输出量得以维持，最大心率下降，由增加的最大每搏输出量进行代偿。最值得注意的是，这些男性在20岁时（1966年）卧床休息3周对身体工作能力的影响比30年的衰老影响更为深远。
