Method:

First, dumbbells bend.

Technical essentials: keep the body upright, hold the dumbbell in front of you with both hands, hold the body with the upper arm, exert force on the biceps brachii and bend the forearm at the elbow joint. Lift the dumbbell and bend it as much as possible. Then, under the control of biceps brachii, slowly return to the original road and put it as far as possible.

Second, bend your arm with one hand

Technical essentials: Sit your legs apart, hold your head high and lean forward, hold the upper arm on one side of the dumbbell hard, try to lift the dumbbell, stay for a while, and then slowly recover under the control of the upper arm.