The focusing muscle (ciliary muscle), which controls the shape of the lens, is thus in a constant state of contraction.

这种控制晶体形状的调焦肌肉(睫状肌)，长期处于收缩状态。

youdao

Such a feeling may be compounded by general fatigue, including a lack of sleep, or by specific muscle overuse related to long hours of focusing on, say, a computer monitor.

引起这种感觉的疲劳因素有很多种，包括睡眠缺乏，或者长时间注视一个地方，如电脑显示器，导致的部分肌肉过度使用。

youdao

In general, warm up by focusing first on large muscle groups, such as your hamstrings.

通常，热身首先注重在在大的肌肉群，例如你的大腿。

youdao

Extending the UnNap Nap To make the UnNap Nap as close to a nap as possible, do a mental scan of the body, focusing on different muscle groups one at a time, stopping at any that are feeling tense.

CNN: How to relax at work