拇指球是指手掌上，拇指下面到手腕中部的三角形肌肉组织。主要的肌肉包括：拇指对掌肌、拇短展肌、拇短屈肌等。
目标速度影响鼠标、食指操作追踪球和拇指操作追踪球等指点装置的操作可控性、稳定性和疲劳度。
Target speed has an effect on the operating controllability, stability and fatigue degree of mouse, and the index finger operating and thumb operating trackballs.
在图片“A”你能看手腕向后摆动时， 一部分的球的重量会移向拇指的下部。
In picture "A" above you can see with the wrist bent back that part of the weight of the ball will be resting on the base of the thumb.
大鼠的脑中，嗅球有蚕豆那么大，兔子脑中的有你的小手指那么大，而寻血犬脑中的有拇指那么大。
It's bean-sized in a rat, about the size of your little finger in a rabbit, and the size of your thumb in a bloodhound.
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