The purpose of using the swim paddle is to increase the level of the palm of the hand, thereby enhancing the sense of water throughout the stroke. When you are swimming, the hand paddle help you to experience the appropriate stroke angle for each stroke stage. If used properly, swim paddle will play a substantial role in the study of the neuromuscular system. Repeated practice of water strokes with your swim paddle will naturally adjust the hand's stroke angle, especially for those who have not practiced paddling with a hand paddle.
Most swim paddle have rubber bands that hold the wrists and fingers. Many coaches recommend using the swim paddle to remove the rubber band that secures the wrists so that the palms can be properly and improperly angled because the swim paddle only have rubber fingers that hold the fingers. When the palm enters the water at the wrong angle, the swim paddle will shake or even fall.
The hand paddle is preferably slightly larger than the palm of your hand. If it is much larger than the palm of your hand, it will cause the shoulder to be treated harshly (swimming shoulder pain).
The propulsion in swimming is caused by the combined force of the arm's resistance and lift (here we don't involve the role of the water and the vertical axis of the body, the horizontal axis swings to produce propulsive force), when you do the rocking practice, Handcuffs are a great tool for experiencing and improving the angle of the stroke. But the swim paddle is much larger than the palm of your hand and is not suitable for this kind of exercise.