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Almost any amount and type of physical activity may slow aging deep within our cells, a new study finds. And middle age may be a critical time to get the process rolling, at least by one common measure of cell aging. 一项新研究发现，不论运动量如何，几乎所有种类的体育活动都能延缓深藏于我们细胞内部的衰老过程。而中年可能是让这一机制继续运行下去的关键时段，至少，就衡量细胞衰老的一个常用指标而言确是如此。 Dating a cell’s age is tricky, because its biological and chronological ages rarely match. A cell could be relatively young in terms of how long it has existed but function slowly or erratically, as if elderly. 确定细胞的年龄可是个棘手差事，因为它们的生物学年龄（表明其组织结构和生理功能的状态）和实际年龄基本上对不上号。有些细胞论其存在时间可能还算年轻，但它们执行起生理机能来却十分缓慢或者不稳定，就如同衰老的细胞一样。 Today, many scientists have begun determining a cell’s biological age — meaning how well it functions and not how old it literally is — by measuring the length of its telomeres. 如今，许多科学家开始通过测量细胞的端粒长度来确定它的生物学年龄。 For those of us who don’t know every portion of our cells’ interiors, telomeres are tiny caps found on the end of DNA strands, like plastic aglets on shoelaces. They are believed to protect the DNA from damage during cell division and replication. | 
