Tuesday, July 12, 2011

Babies' Firsts: The Science Behind Rolling Over

A few weeks ago, as part of our Babies’ Firsts series, we had the following questions for our readers:
  1. How old was your baby when he or she rolled over for the first time?
  2.  Did your baby roll from back-to-tummy or tummy-to-back first and how long did it take before he or she could roll both ways?
  3. What kind of adjustments or modifications did you have to make in your baby's environment to accommodate his or her new skill?
First, we’d like to thank everyone who commented! Your stories show that every baby is different and that even siblings who grow up in the same environment achieve milestones, like rolling over, at their own pace. Today, I’ll share the story about when my youngest daughter, Charlotte, learned to roll over and then explain what research shows about how and when babies tend to develop this important skill.

Charlotte’s Story
Charlotte is 7 months old now and she’s been rolling over for 3 ½ months. She first rolled from her back to her tummy while we were playing together on the floor. Although we had been having “tummy time” a few times each day, she never seemed to like it, so when she first rolled over, she promptly started crying. I helped her roll back onto her back, but within just a few minutes she was back on her tummy again. It went on like this for a few weeks until she learned to roll from her tummy to her back.

We had to make quite a few changes when Charlotte started rolling over. We had to be much better about keeping the floor clean and making sure that her big sister, Olivia, picked up her toys. We also had to start keeping all the dog toys out of reach and I bought a foam play mat to make our hard floor a little softer for her. All of the effort came in handy, because before long she was army crawling all over the house (but that story is for another post!).

Rolling Over Research
Everyone knows that there are 2 ways babies must learn to roll, from back-to-tummy and tummy-to-back, but many people (including me, until today) may not know that within each of these rolling methods there are 2 types, with and without rotation. Here is information about each type:

Prone to supine (tummy-to-back)
  • Without rotation – Rolling from tummy-to-back without rotation means that the shoulder and pelvis are aligned, body is extended, and the movement starts from the head.  It can start as early as 1 month of age, but only about 10% of babies can roll this way by 3 months; 50% and 90% achieve it by 6 and 8 ½ months, respectively.    
  • With rotation – Rolling from back-to-tummy with rotation is characterized by a shoulder and pelvis that are not aligned, movement originating from the shoulder, pelvis, or head, and rotation in the body.  Because the rotation is a more complicated movement, this type of rolling typically starts around 4 months with 50% achieving it by 7 months and 90% by about 9 months.
Supine to prone (back-to-tummy)
  • Without rotation – When a baby rolls from back-to-tummy without rotation, his head will be up, his body will be stretched and his shoulder will be in line with his pelvis. The movement will begin from the head, shoulder or hip, and his body will move as one unit. Fifty percent of babies can roll this way by about 5.5 months and 90% reach this milestone by 9 months.
  • With rotation – Rolling this way requires the baby to lift his head and stretch his body and the movement starts from the head, shoulder, or hip, but the shoulder and pelvis will not be aligned, the baby’s body will rotate, and the legs will move separately from the rest of the body. Just as with tummy-to-back, rolling with rotation is mastered a little later than rolling without; 50% achieve it by 7 months and 90% by 9 months.
So, the take-away message: The age at which babies master rolling over varies greatly! If you think about it, it makes sense given that rolling over requires the coordination and use of many muscle groups.  Regardless of the age of your baby, rolling over means that you have some baby-proofing to do! For more information, refer to Baby Proofing Part 1 (for birth to 6 months) and Part 2 (for 6-12 months).

Piper M, Darrah J. Motor Assessment of the Developing Infant. Philadelphia PA:W.B. Saunders Company 1994.

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