Messa Guy A M, Piasecki Mathew, Rittweger Jörn, McPhee Jamie S, Koltai Erika, Radak Zsolt, Simunic Bostjan, Heinonen Ari, Suominen Harri, Korhonen Marko T, Degens Hans
Department of Life Sciences, Research Centre for Musculoskeletal Science and Sports Medicine, Manchester Metropolitan University, Manchester, UK.
MRC-Versus Arthritis Centre for Musculoskeletal Ageing Research and National Institute for Health Research (NIHR) Nottingham Biomedical Research Centre, University of Nottingham, Nottingham, UK.
Scand J Med Sci Sports. 2020 Nov;30(11):2057-2069. doi: 10.1111/sms.13778. Epub 2020 Aug 28.
The aging-related loss of muscle mass is thought to be partly attributable to motor neuron loss and motor unit remodeling that result in fiber type grouping. We examined fiber type grouping in 19- to 85-year-old athletes and non-athletes and evaluated to which extent any observed grouping is explained by the fiber type composition of the muscle. Since regular physical activity may stimulate reinnervation, we hypothesized that fiber groups are larger in master athletes than in age-matched non-athletes. Fiber type grouping was assessed in m. vastus lateralis biopsies from 22 young (19-27 years) and 35 healthy older (66-82 years) non-athletes, and 14 young (20-29 years), 51 middle-aged (38-65 years), and 31 older (66-85 years) athletes. An "enclosed fiber" was any muscle fiber of a particular type surrounded by fibers of the same type only. A fiber type group was defined as a group of fibers with at least one enclosed fiber. Only type II fiber cross-sectional area (FCSA) showed an age-related decline that was greater in athletes (P < .001) than in non-athletes (P = .012). There was no significant age-related effect on fiber group size or fiber group number in athletes or non-athletes, and the observed grouping was similar to that expected from the fiber type composition. At face value, these observations do 1) neither show evidence for an age-related loss and remodeling of motor units nor 2) improved reinnervation with regular physical activity, but 3) histological examination may not reveal the full extent of aging-related motor unit remodeling.
与衰老相关的肌肉质量流失被认为部分归因于运动神经元丧失和运动单位重塑，这会导致肌纤维类型分组。我们研究了19至85岁运动员和非运动员的肌纤维类型分组情况，并评估了所观察到的分组在多大程度上可由肌肉的肌纤维类型组成来解释。由于规律的体育活动可能刺激神经再支配，我们推测，与年龄匹配的非运动员相比，老年运动员的肌纤维组更大。对22名年轻（19至27岁）和35名健康老年（66至82岁）非运动员以及14名年轻（20至29岁）、51名中年（38至65岁）和31名老年（66至85岁）运动员的股外侧肌活检样本进行了肌纤维类型分组评估。“封闭纤维”是指仅被相同类型的纤维包围的特定类型的任何肌纤维。肌纤维类型组被定义为一组含有至少一根封闭纤维的纤维。仅II型肌纤维横截面积（FCSA）显示出与年龄相关的下降，且运动员中的下降幅度（P <.001）大于非运动员（P =.012）。在运动员或非运动员中，未发现与年龄相关的对肌纤维组大小或肌纤维组数量的显著影响，且观察到的分组与根据肌纤维类型组成预期的分组相似。表面上看，这些观察结果1）既未显示出与年龄相关的运动单位丧失和重塑的证据，也未显示出2）规律体育活动带来的神经再支配改善，但3）组织学检查可能无法揭示与衰老相关的运动单位重塑的全部程度。
