Between tummy time and crawling, there are two important reflexes developing. First is the Symmetrical Tonic Neck Reflex (STNR) also known as the crawling reflex. STNR is a transitional reflex that helps babies change from being on their belly to up on their hands and knees. Through lots of crawling, the STNR will fully integrate (disappear) at about 1 year. If it doesn’t, it may contribute to challenges with skills such as posture, balance and hand-eye coordination potentially requiring future therapeutic intervention.
Next is an infant’s Asymmetrical Tonic Neck Reflex (ATNR) which should fully integrate by approximately 6 months. This reflex is what causes a baby’s arm and leg to stretch in the direction they are looking while the other arm and leg will flex or bend. The ATNR reflex actually develops in utero but is encouraged through tummy time as babies develop the ability to push themselves up off the floor with their hands and turn their head to look around with more neck control.
These reflexes develop more fully through tummy time and crawling, and a lack of integration may have future developmental effects. For example, Dr. Miriam Bender wrote in “Stopping ADHD” that at least 75% of the learning-disabled people surveyed had an immature STNR contributing to their disability.
There is growing evidence that crawling plays a vital role in an infant’s early childhood development. It helps with strengthening the trunk or core, improved balance, better spinal alignment, enhanced visual-spatial skills, improved socio-emotional development and, as some studies suggest, may help avoid future learning problems.
First, crawling will help to develop the muscles and joints near the center of the body – the tummy, back, neck, hips and shoulders – which will play an important role in improved gross and fine motor skills, balance, hand-eye coordination and overall strength.
Equally important is the advancement of bilateral coordination. Crawling allows babies to create connections between both cerebral hemispheres. When infants coordinate their movements they first move one arm and the opposite leg then the other arm and the opposing leg in reciprocating motion; this is called cross-crawl patterning. The nerve impulses originate in each side of the brain cortex and cross at the brain stem in the corpus callosum to send the signal to the opposite arm or leg. When an infant is crawling their brain is developing neurological routes to help send these signals quickly back and forth. With the exception of rock-wall climbing, crawling is the only activity that will encourage the development of these patterns.
Additionally, it’s important to take into account the typically unrecognized physical benefits of crawling such as: the development of the arches of the hand; the lengthening of the finger muscles; the recognition of the skill side of the hand (the side with the thumb) and the stabilizing side of the hand; as well as the development of the muscles in the hand especially the “web space” next to the thumb which affects future pencil grip ability.