To be a sportsman, start by exercising your arms!

　　The muscle training status of the human body is determined by the activity status. When you focus on activities of the wrist joint, the muscles trained are mainly the forearm muscles. ； If the elbow joint is the main focus, the muscles trained are the upper arms. ； When focusing on the shoulder joint, the muscles trained are related muscles of the shoulder. In other words, the muscles of the proximal limbs of the movable joints (close to the driving trunk) are the main muscles of the joints. Of course, this part is the main part during training.

　　Although the hand is holding a dumbbell, if the wrist joint is the main activity, instead of evenly distributing the contraction and extension, abduction and retraction of the wrist, the contraction and extension of the elbow joint, the contraction and extension of the shoulder joint, abduction and retraction, horizontal abduction and horizontal retraction, internal rotation and external rotation, rotation, etc., then the hand muscles can be truly and effectively trained.

　　The weight of dumbbells is limited, but compared to the muscles of the hands, forearms, upper arms, and shoulders, the training of distal muscles is mainly about muscle strength, while the training of proximal muscles is mainly about muscle endurance, and the natural effects are different.

　　When you want to train the strength and muscle mass of your arms, the weight of dumbbells is only effective for the muscles of the hands and forearms. For upper arm and shoulder muscle training, heavier weights are needed to easily show the effect of muscle strength training. Weights that are too light can only train muscle endurance.

　　Muscle strength training requires the cooperation of the whole body. Not only is local training ineffective, but it is also easy to deteriorate again. If the muscle strength of the expelling muscles is not good, and the muscle strength of the chest and back is insufficient, it will not be easy to show the muscles of the shoulders.