Train Triceps, avoid loose, flabby upper arm. Improve muscle tone.

练习肱三头肌，防止上臂肌肉松弛。

youdao

To bend the arm at the elbow, the muscle at the front of the upper arm has to shorten and bunch up.

同时肘部轻轻弯曲，胳膊向后伸，这样你的肱二头肌就压在耳边了。

youdao

For example, the bicepes muscle in the front of the upper arm is a flexor. When this muscle contracts, the elbow bends and the forearm and hand move toward the shoulder.

具体说，前上臂的肱二头肌就是一块屈肌，当它运动时，肘部弯曲，前臂和手就向肩部运动。

youdao