The bodybuilders contracted their biceps in unison.

美运员们一起收缩肱二头。

The article explains the morphology factor of chinning in combined grip. It points out that chinning movement can well-developed muscles such as pectoralis major, latissimus dorsi and biceps brachii.

文章阐述了正握引体比反握引体难做的因素,明确了做引体作,主要用来发展胸大、背阔和肱二头的力,发达这些肉的肉块。