Advanced age has been shown to result in decreased compliance, shortening velocity, and calcium sensitivity of the heart muscle. Even though cardiac health has been studied extensively in elderly populations, relatively little is known about cardiac health and age for the first part of adulthood. The purpose of this study was to compare cardiac contractile properties across the first year of life in rats (between 17–53 weeks), corresponding to early to mid-adulthood.

Hearts were harvested from rats aged 17-, 24-, 36-, and 53-weeks. Skinned cardiac trabecular fibre bundle testing was used to evaluate active and passive force properties, maximum shortening velocity, calcium sensitivity, and myosin heavy chain isoforms.

Maximum active stress production was not different between age groups. Calcium sensitivity increased progressively, while shortening velocity remained unchanged after an increase from 17-and 24-weeks. Passive stiffness decreased between 17- and 24-weeks, but then increased progressively through to 53-weeks. Thus, many of the observed detrimental changes in systolic function (reduced shortening velocity and calcium sensitivity) associated with aging, do not seem to occur in early to mid-adulthood, while early signs of increased diastolic stiffness manifest within 53 weeks of age and may represent a first sign of decreasing heart function and health.

已显示高龄会导致心肌的顺应性降低、速度缩短和钙敏感性降低。尽管已经对老年人群的心脏健康进行了广泛的研究，但对成年初期的心脏健康和年龄知之甚少。本研究的目的是比较大鼠生命第一年（17-53 周之间）的心脏收缩特性，对应于成年早期到中期。

从 17 周、24 周、36 周和 53 周的大鼠中采集心脏。剥皮心脏小梁纤维束测试用于评估主动和被动力特性、最大缩短速度、钙敏感性和肌球蛋白重链亚型。

不同年龄组的最大主动应激产生没有差异。钙敏感性逐渐增加，而缩短速度在从 17 周和 24 周增加后保持不变。被动僵硬在 17 周和 24 周之间下降，但随后逐渐增加到 53 周。因此，许多观察到的与衰老相关的收缩功能的有害变化（缩短速度和钙敏感性降低）似乎不会发生在成年早期至中期，而舒张期僵硬增加的早期迹象在 53 周龄内出现，并且可能代表心脏功能和健康下降的第一个迹象。