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Gross and Fine Motor Skills
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Motor skills are simply developing your child's ability to manipulate and control muscle movements and strength. Gross movements are large movements, involving the whole body or large muscle groups. Fine motor skills focuses on the ability to make small, accurate movements. It is important to develop both of these skills in your child's journey in becoming a writer. As a general rule you will find that the main focus of development is on gross motor skills before the focus shifts to fine motor movements however at all points both skill sets should be developing. Below is an example of the development of movements and skill progressions before your child begins to write letters:

Gross Motor Skills
Early kicking and moving of limbs from birth. At this point babies are beginning to understand that they can control their movements and have limited accuracy.
Babies develop an intention and increasing accuracy in their movements. Such as learning to role over or hold up their heads.
As children get older, play is vital in developing gross motor skills. Play inside and outside of the home provide different opportunities to develop accuracy and strength in their muscles. In strength development children want to develop both the power and stamina in their muscles. In schools one of the key complaints children make when writing is that it 'hurts'. This can put children off of writing and learning. For these children they need to return to developing their muscle strength and stamina.
Children need good core strength to be able to sit up write at a table for a period of time. They need to be able to move their arm from the shoulder.
Why not try playing different games? Swinging in the park? Climbing? Crawling like a cat? Jumping as high as a kangaroo? Swimming? Catch with a ball?

Fine Motor Skills
Early fine motor skills would include movements such as finger sucking. This is also a clear example of how fine motor accuracy is dependant on children also using gross motor skills. In this example the accuracy required to get the selected fingers or thumb into their mouth requires a whole arm movement to lift the fingers to their face.
For young children, eating is one of their first opportunities to flex their fine motor skills. Allowing children to feed themselves gives them a sense of purpose for developing their fine motor skills and accuracy. What better motivation to try something new then tasty food. It certainly helps motivate us! As they are learning, the process will be messy but it is a wonderful example of developing learning skills. Understanding that we fail and learn from those attempts.
Children need good finger strength to be able to hold a pencil and control it. Playing lots of games which involve smaller movements and items are great as your child develops. Make sure to keep these age appropriate as children can choke of small items.