Degens H
Department of Clinical Neurophysiology, Karolinska Hospital, Stockholm, Sweden.
Adv Exp Med Biol. 1998;454:343-8. doi: 10.1007/978-1-4615-4863-8_40.
The age-related reduction in exercise capacity is associated with a reduction in cardiac output and maximal oxygen consumption (VO2max). The loss of muscle mass explains a large portion of the age-related decline in VO2max. The capillary supply to a muscle fibre is primarily determined by its size, but also by its metabolic profile and the metabolic profile of surrounding fibres. Thus the age-related fibre atrophy and changes in the fibre type composition are expected to be accompanied by changes in the capillarisation. The exchange of oxygen, blood-borne energy sources, metabolites and heat between the blood and muscle tissue takes place in the microcirculation. Changes in the microcirculation may thus affect the functioning and viability of the muscle. The resting blood flow is minimally affected by age, but blood flow during or following exercise is generally reduced. This may in part be due to a reduced vasodilatory capacity and a decreased capillarisation. However, the coupling between capillary supply to a fibre and its metabolic profile or the profile of the surrounding fibres is maintained. There are some changes in ultrastructure of the endothelium. The age-related changes in the microcirculation are associated with a reduced VO2max and exercise capacity. The adaptability of the microcirculation is maintained at old age.
与年龄相关的运动能力下降与心输出量和最大耗氧量（VO2max）降低有关。肌肉量的减少在很大程度上解释了与年龄相关的VO2max下降。肌肉纤维的毛细血管供应主要由其大小决定，但也受其代谢特征和周围纤维代谢特征的影响。因此，与年龄相关的纤维萎缩和纤维类型组成的变化预计会伴随着毛细血管化的改变。血液与肌肉组织之间的氧气、血源性能量来源、代谢物和热量交换发生在微循环中。微循环的变化可能会影响肌肉的功能和活力。静息血流量受年龄影响最小，但运动期间或运动后的血流量通常会减少。这可能部分归因于血管舒张能力降低和毛细血管化减少。然而，纤维的毛细血管供应与其代谢特征或周围纤维的代谢特征之间的耦合得以维持。内皮的超微结构存在一些变化。微循环中与年龄相关的变化与VO2max降低和运动能力下降有关。微循环的适应性在老年时得以维持。
