So why are pediatricians pushing “tummy time” so much? With the “Back to Sleep campaign” and increased time spent in bouncers, semi-lying container like devices, car seats, and flat bed strollers the truth is that infants are spending the majority of their day either semi-lying or horizontal—i.e. on their backs.
It may seem that horizontal/versus upright positioning might be more gentle on little infants spines. However, if you are always lying on a group of muscles it subsequently impedes your ability to use them. Visualize, for a moment, how much an infant is working or contracting her neck muscles in an infant car seat [out of the car]—not.very.much.
Weak neck muscles lead to an imbalance in the front, back, and sides of the body. This leads to babies that are struggling to engage in activities that require them to control their heads. Which in turn leads to a delay in self-initiated mobility.
If a baby can’t roll, move to sit independently, or crawl she is left to lie there, spending even more time on her back. A vicious circle. She is left at a definite disadvantage if she ends up in a dangerous or undesirable position and her muscles are weak (from lack of activation).