Always fix the two upper arms to the side, only the forearm can move. Don't relax at the highest point, and don't relax at the lowest point, so that the biceps brachii always keeps a certain tension. Don't hold the dumbbell too tightly, pay attention to the experience? Peak contraction? The burning sensation brought by the position. Continue to tighten at the peak position 1-3 seconds. It is better to train with centrifugal force. When lowering and restoring, try to be slow and don't be discouraged.