A study on changes in flexibility by growth and aging and development of the methodology to improve flexibility

在本研究项目中，我将灵活性定义为关节的活动范围（ROM），并以以下三个目标进行了一系列研究，即，1)阐明ROM的决定因素，相对于肌肉肌腱的属性，2）澄清性别差异和影响的增长和老化的ROM和他们的决定因素，和3）调查ROM的可塑性。为了这些目的，我开发了一个系统，被动ROM测量在一个良好控制的负载条件和伸展性的肌肉肌腱单位在体内进行了测量。在整个系列研究中，我通过研究小腿三头肌和胫骨前肌的行为，重点关注踝关节跖屈和背屈ROM。获得了以下结果。1)结果表明，ROM应在被动和主动条件下进行评估，并选择肌肉的大小，强度和肌肉肌腱单位的弹性特性作为被动和主动ROM的决定因素。2）ROM存在性别差异（女性大于男性），特别是与肌腱的伸展性有关，但这种关系是年龄的函数。3)肌肉的静态拉伸导致ROM的增加，伴随着肌腱的进一步伸长，而不是肌纤维。卧床休息引起ROM和肌腱特性的类似变化。此外，肌肉的大小，力量，建筑和肌肉肌腱力学性能之间的相互依存关系进行了详细的研究。对被动延长、主动收缩引起的肌肉-肌腱单位变形与关节扭矩之间关系的研究表明，肌肉-肌腱的力学性能具有可塑性，这表明这些程序作为改善ROM的方法的潜力。

In the present research project, I defined flexibility as the range of motion (ROM) of the joint, and carried out a series of studies with the following three aims, i.e., 1) to elucidate determinants of ROM, with respect to musculotendinous properties, 2) to clarify gender differences and effects of growth and aging on ROM and their determinants, and 3) to investigate the plasticity of ROM. For these aims, I developed a system with which passive ROM was measured in a well-controlled loading condition and extensibility of the muscle-tendon unit was measured in vivo. Throughout the series of studies, I focused on ankle plantar-and dorsi-flexion ROM by studying behavior of the triceps surae and tibialis anterior muscles. The following findings were obtained. 1) It was shown that ROM should be evaluated both in passive and active conditions, and that muscle size, strength, and elastic properties of the muscle-tendon unit were selected as determinants of passive and active ROM. 2) There was a gender difference in ROM (women larger than men) that was related particularly with extensibility of the tendon, but the relationship was a function of age. 3) Static stretching of the muscles resulted in an increase in ROM that was accompanied by further elongation of tendon but not of muscle fibers. Bed rest induced similar changes in ROM and tendon properties. Furthermore, the interdependence among muscle size, strength, architecture, and musculotendinous mechanical properties was studied in detail. Studies on the relationship between deformation of the muscle-tendon unit induced by passive lengthening, active contractions and joint torque indicated the possibility of plasticity of musculotendinous mechanical properties, suggesting potentials of these procedures as the way to improve ROM.