INTRODUCTION Ageing is associated with an attenuated hypertrophic response to resistance training and periods of training interruptions. Hence, elderly would benefit from the 'muscle memory' effects of resistance training on muscle strength and mass during detraining and retraining. As the underlying mechanisms are not yet clear, this study investigated the role of myonuclei during training, detraining and retraining by using PCM1 labelling in muscle cross-sections of six older men. METHODS Knee extension strength and power were measured in 30 older men and 10 controls before and after 12 weeks resistance training and after detraining and retraining of similar length. In a subset, muscle biopsies from the vastus lateralis were taken for analysis of fibre size, fibre type distribution, Pax7+ satellite cell number and myonuclear domain size. RESULTS Resistance training increased knee extension strength and power parameters (+10 to +36%, p < .001) and decreased the frequency of type IIax fibres by half (from 20 to 10%, p = .034). Detraining resulted in a modest loss of strength and power (-5 to -15%, p ≤ .004) and a trend towards a fibre-type specific decrease in type II fibre cross-sectional area (-17%, p = .087), type II satellite cell number (-30%, p = .054) and type II myonuclear number (-12%, p = .084). Less than eight weeks of retraining were needed to reach the post-training level of one-repetition maximum strength. Twelve weeks of retraining were associated with type II fibre hypertrophy (+29%, p = .050), which also promoted an increase in the number of satellite cells (+72%, p = .036) and myonuclei (+13%, p = .048) in type II fibres. Changes in the type II fibre cross-sectional area were positively correlated with changes in the myonuclear number (Pearson's r between 0.40 and 0.73), resulting in a stable myonuclear domain. CONCLUSION Gained strength and power and fibre type changes were partially preserved following 12 weeks of detraining, allowing for a fast recovery of the 1RM performance following retraining. Myonuclear number tended to follow individual changes in type II fibre size, which is in support of the myonuclear domain theory.

中文翻译：

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阻力训练，训练和再训练对老年男性的肌肉力量和力量，肌纤维大小，卫星细胞和肌核的影响。

简介衰老与抵抗训练和训练中断时间的肥大性反应减弱有关。因此，老年人将在训练和再训练过程中受益于阻力训练对肌肉力量和质量的“肌肉记忆”效应。由于潜在的机制尚不明确，本研究通过使用PCM1标记在6名老年男性的肌肉横断面中研究了肌核在训练，训练和再训练过程中的作用。方法在30周的老年男性和10位对照中，在12周的阻力训练前后以及类似的长度的训练和再训练之后，测量膝关节的伸直力量和力量。在一个子集中，对外侧股肌进行肌肉活检，以分析纤维大小，纤维类型分布，Pax7 +卫星细胞数和肌核结构域大小。结果阻力训练增加了膝盖伸展力量和力量参数（+10至+ 36％，p <.001），并将IIax型纤维的频率降低了一半（从20％至10％，p = .034）。训练导致强度和功率的适度损失（-5至-15％，p≤.004），并且II型纤维截面积的纤维型特定减小趋势（-17％，p = .087） ），II型卫星细胞数（-30％，p = .054）和II型肌核细胞数（-12％，p = .084）。只需不到八周的再培训即可达到一次重复最大力量的训练后水平。再训练十二周与II型纤维肥大有关（+ 29％，p = .050），这也促进了卫星细胞数量（+ 72％，p = .036）和肌核（+ 13％， p = .048）在II型纤维中。II型纤维横截面积的变化与肌核数的变化呈正相关（Pearson r在0.40至0.73之间），从而形成稳定的肌核结构域。结论训练12周后，部分保留了获得的强度，功率和纤维类型的变化，从而可以在训练后快速恢复1RM性能。肌核数目倾向于随II型纤维大小的个体变化而变化，这支持了肌核结构域理论。允许在重新培训后快速恢复1RM性能。肌核数目倾向于随II型纤维大小的个体变化而变化，这支持了肌核结构域理论。允许在重新培训后快速恢复1RM性能。肌核数目倾向于随II型纤维大小的个体变化而变化，这支持了肌核结构域理论。