Institute of Physical Education, Health and Leisure Studies, National Cheng-kung University, Tainan, Taiwan.
Calcif Tissue Int. 2010 Feb;86(2):142-53. doi: 10.1007/s00223-009-9320-0. Epub 2009 Dec 3.
The purpose of this study is to investigate the effects of non-weight-bearing exercise on growing bone. Male Wistar rats (7 week-old) were assigned to one baseline control group, one control group and two swimming training groups, which were trained with 2 and 4% body-weight mass added, respectively. After an 8-week training period, three groups showed significant development compared to the baseline control group. Among the three 15-week-old groups, swimming-trained rats were lower in body weight (BW), densitometry and size-related measurements. In femoral biomechanical testing, swimming training groups were significantly lower in yield moment and ultimate moment, which may be due to a significantly lower long bone cross-sectional moment of inertia. However, the two swimming groups were higher in post-yield energy absorption and displacement. Further, in estimated tissue-level biomaterial properties, no differences were shown in yield stress, strain or toughness among the three groups. Using BW as a covariate, results of ANCOVA showed no differences in size-related parameters among the three groups, and some parameters were even higher in the two swimming groups. Regarding Pearson's correlation, size-related parameters correlated well to BW and whole bone strength but not to tissue post-yield behaviors. In conclusion, when compared to age-matched control group, swimming rats showed lower bone strength and lower yield energy absolutely at the structural level, but similar yield stress and yield toughness at the tissue level. Moreover, swimming training benefited growing bone in post-yield behaviors. Further studies should investigate the parameters that contribute to this exercise-induced post-yield behavior.
本研究旨在探讨非负重运动对生长中骨骼的影响。雄性 Wistar 大鼠（7 周龄）分为基础对照组、对照组和 2%、4%体重附加的两组游泳训练组。经过 8 周的训练期后，三组与基础对照组相比均有显著的生长发育。在三组 15 周龄大鼠中，游泳训练组体重（BW）、骨密度和尺寸相关测量值较低。在股骨生物力学测试中，游泳训练组屈服力矩和极限力矩显著降低，这可能是由于长骨横截面转动惯量显著降低所致。然而，两组游泳训练组的屈服后能量吸收和位移较高。此外，在估计的组织水平生物材料特性中，三组之间的屈服应力、应变或韧性没有差异。使用 BW 作为协变量，ANCOVA 结果显示三组之间的尺寸相关参数没有差异，有些参数在两组游泳组中甚至更高。关于 Pearson 相关性，尺寸相关参数与 BW 和整个骨骼强度相关性良好，但与组织屈服后行为相关性不佳。总之，与同龄对照组相比，游泳大鼠在结构水平上表现出较低的骨强度和较低的屈服能量，但在组织水平上具有相似的屈服应力和屈服韧性。此外，游泳训练对生长中的骨骼在屈服后行为中有益。应进一步研究导致这种运动诱导的屈服后行为的参数。
