Proctor D N, Sinning W E, Walro J M, Sieck G C, Lemon P W
Applied Physiology Research Laboratory, School of Exercise, Leisure, and Sport, Kent State University 44242, Ohio, USA.
J Appl Physiol (1985). 1995 Jun;78(6):2033-8. doi: 10.1152/jappl.1995.78.6.2033.
Morphometry and oxidative capacity of slow-twitch (type I) and fast-twitch (type IIa and IIb) muscle fibers obtained from vastus lateralis needle biopsies were compared between younger (21-30 yr) and older (51-62 yr) normal fit (maximal O2 uptake = 47.0 vs. 32.3 ml.kg-1.min-1) and endurance-trained (66.3 vs. 52.7 ml.kg-1.min-1) men (n = 6/group). The older groups had smaller type IIa (31%) and IIb (40%) fiber areas and fewer capillaries surrounding these fibers than did younger groups. The reduced type II fiber areas and capillary contacts associated with aging were also observed in the older trained men. However, the capillary supply per unit type II fiber area was not affected by age but was enhanced by training. Additionally, on the basis of quantitative histochemical analysis, succinate dehydrogenase activities of type IIa fibers in the older trained men [4.07 +/- 0.68 (SD) mmol.min-1.l-1] were similar to those observed in younger trained men (4.00 +/- 0.48 mmol.min-1.l-1) and twofold higher than in older normal fit men (2.01 +/- 0.65 mmol.min-1.l-1; age x fitness interaction, P < 0.05). Type I muscle fibers were unaffected by age but were larger and had more capillary contacts and higher succinate dehydrogenase activities in the trained groups. The findings of this study suggest that aging results in a decrease in type II fiber size and oxidative capacity in healthy men and that this latter effect can be prevented by endurance training. Conclusions regarding the effects of age and training status on muscle capillarization depend largely on how these data are expressed.
对从外侧股四头肌针吸活检获取的慢肌纤维（I型）和快肌纤维（IIa型和IIb型）的形态测量和氧化能力进行了比较，研究对象为年轻（21 - 30岁）和年长（51 - 62岁）的正常健康男性（最大摄氧量分别为47.0与32.3 ml·kg⁻¹·min⁻¹）以及耐力训练男性（分别为66.3与52.7 ml·kg⁻¹·min⁻¹）（每组n = 6）。与年轻组相比，年长组的IIa型（31%）和IIb型（40%）纤维面积更小，且这些纤维周围的毛细血管更少。在年长的训练男性中也观察到与衰老相关的II型纤维面积减小和毛细血管接触减少。然而，单位II型纤维面积的毛细血管供应不受年龄影响，但训练可使其增加。此外，基于定量组织化学分析，年长训练男性IIa型纤维的琥珀酸脱氢酶活性[4.07 ± 0.68（标准差）mmol·min⁻¹·l⁻¹]与年轻训练男性（4.00 ± 0.48 mmol·min⁻¹·l⁻¹）相似，且比年长正常健康男性（2.01 ± 0.65 mmol·min⁻¹·l⁻¹）高两倍（年龄×健康状况交互作用，P < 0.05）。I型肌纤维不受年龄影响，但在训练组中更大，有更多的毛细血管接触且琥珀酸脱氢酶活性更高。本研究结果表明，衰老导致健康男性II型纤维大小和氧化能力下降，而耐力训练可预防这种影响。关于年龄和训练状态对肌肉毛细血管化影响的结论在很大程度上取决于这些数据的呈现方式。
