She was going to have quadriceps and deltoids.

她本来就有股四头和三。

I learned that word a couple of weeks ago, deltoid.

几周前，我学会了这个词，三。

And why the arm muscle, called the deltoid, in the top of the shoulder?

为什么手臂肉， 称为三， 在肩膀顶部？

Adults and children ages three and older tend to receive vaccines in their upper arm in the deltoid.

成人和 3 岁及以上儿童倾向于在上臂三中接种。

For instance, many vaccines are injected in the deltoid because it is close to lymph nodes located just under the armpit.

例如，许注射在三中， 因为它靠近位于腋下淋巴结。

But when it's time to start abducting her arms from her side to over her head, those deltoids now become the primary movers, while the pecs and lats switch to being antagonists.

但是当她开始将手臂从身体一侧转移到头顶时，三现在成为主要运动者，而胸和胸则变成了对手。

So, in this case, the antagonists of the jumping jacks would include the deltoids on top of her shoulders, which among other things help her slow her down arms so that she doesn't slap her thighs too hard.

所以，在这种情况下，开合跳对抗肉包括她肩膀上三有助于她放慢手臂速度，这样她就不会用力拍打大腿。