Human Performance Laboratory, Ball State University, Muncie, Indiana 47306, USA.
J Appl Physiol (1985). 2012 Nov;113(9):1495-504. doi: 10.1152/japplphysiol.00786.2012. Epub 2012 Sep 13.
To examine potential age-specific adaptations in skeletal muscle size and myofiber contractile physiology in response to aerobic exercise, seven young (YM; 20 ± 1 yr) and six older men (OM; 74 ± 3 yr) performed 12 wk of cycle ergometer training. Muscle biopsies were obtained from the vastus lateralis to determine size and contractile properties of isolated slow [myosin heavy chain (MHC) I] and fast (MHC IIa) myofibers, MHC composition, and muscle protein concentration. Aerobic capacity was higher (P < 0.05) after training in both YM (16 ± 2%) and OM (13 ± 3%). Quadriceps muscle volume, determined via MRI, was 5 ± 1 and 6 ± 1% greater (P < 0.05) after training for YM and OM, respectively, which was associated with an increase in MHC I myofiber cross-sectional area (CSA), independent of age. MHC I peak power was higher (P < 0.05) after training for both YM and OM, while MHC IIa peak power was increased (P < 0.05) with training in OM only. MHC I and MHC IIa myofiber peak and normalized (peak force/CSA) force were preserved with training in OM, while MHC I peak force/CSA and MHC IIa peak force were lower (P < 0.05) after training in YM. The age-dependent adaptations in myofiber function were not due to changes in protein content, as total muscle protein and myofibrillar protein concentration were unchanged (P > 0.05) with training. Training reduced (P < 0.05) the proportion of MHC IIx isoform, independent of age, whereas no other changes in MHC composition were observed. These data suggest relative improvements in muscle size and aerobic capacity are similar between YM and OM, while adaptations in myofiber contractile function showed a general improvement in OM. Training-related increases in MHC I and MHC IIa peak power reveal that skeletal muscle of OM is responsive to aerobic exercise training and further support the use of aerobic exercise for improving cardiovascular and skeletal muscle health in older individuals.
为了研究有氧训练对骨骼肌大小和肌纤维收缩生理的潜在年龄特异性适应，7 名年轻（YM；20±1 岁）和 6 名老年男性（OM；74±3 岁）进行了 12 周的自行车测力计训练。从股外侧肌中获取肌肉活检，以确定分离的慢（肌球蛋白重链（MHC）I）和快（MHC IIa）肌纤维的大小和收缩特性、MHC 组成和肌肉蛋白浓度。YM（16±2%）和 OM（13±3%）训练后有氧能力均提高（P<0.05）。通过 MRI 确定的股四头肌肌肉体积，YM 和 OM 训练后分别增加了 5±1%和 6±1%（P<0.05），这与 MHC I 肌纤维横截面积（CSA）的增加有关，与年龄无关。YM 和 OM 训练后 MHC I 峰值功率均提高（P<0.05），而 OM 训练后 MHC IIa 峰值功率增加（P<0.05）。OM 训练后 MHC I 和 MHC IIa 肌纤维峰值和标准化（峰值力/CSA）力得到保留，而 YM 训练后 MHC I 峰值力/CSA 和 MHC IIa 峰值力降低（P<0.05）。肌纤维功能的年龄依赖性适应并非由于蛋白质含量的变化所致，因为总肌肉蛋白和肌原纤维蛋白浓度在训练后没有变化（P>0.05）。训练减少了（P<0.05）MHC IIx 同工型的比例，与年龄无关，而 MHC 组成没有观察到其他变化。这些数据表明，YM 和 OM 之间肌肉大小和有氧能力的相对改善相似，而肌纤维收缩功能的适应则表现出 OM 的普遍改善。训练相关的 MHC I 和 MHC IIa 峰值功率增加表明，OM 的骨骼肌对有氧训练有反应，并进一步支持使用有氧运动来改善老年人的心血管和骨骼肌健康。
