Shoulder girdle exercises can increase shoulder stability, which is an essential base for good handwriting. Many children who struggle to control a pencil effectively and whose fine motor skills are poor, lack good stability and control of their shoulder girdle muscles. The following link has wonderful ideas to develop shoulder girdle stability at home. Another fun and simple way to develop these muscles is by elevating the task; the task does not need to be pen and paper activities and can include sticking, building, shaving foam, and more! It can also incorporate many other components such as fine-motor skills, bilateral integration, eye-hand coordination, planning and sensory play; copy designs to introduce a Visual Motor component. Have fun!
https://www.ot-mom-learning-activities.com/shoulder-exercises-for-kids.html
