Head lifting, crawling, climbing and squatting turn an infant's C-shaped spine into 3 adult curves over about 18 years
Infants begin life with a C-shaped spinal posture, and Eileen Durfee's Spinal Fitness book places the development of the adult S-shape across approximately the first 18 years of life. The book reports Dr. John Scherger's finding that the S-shape normally takes approximately 25% of the human lifespan to fully develop, and it names the movements that build the cervical and lumbar curves; it names no specific input for the thoracic curve.
All quadrupeds keep a more C-shaped spinal pattern throughout life, and Chapter 2 of the book explains why that shape suits them: the spine spans horizontally between the 2 front limbs and the 2 rear limbs, and the animal's weight is distributed across 4 contact points. A quadruped also rises from the prone position, belly toward the ground, so its 4 limbs press into the ground while that base supports the spine.
The human spine carries a different load. It stacks the head, rib cage, pelvis and legs vertically on 2 legs under gravity, and it must let the body rise from the supine position, on the back, which the book describes as a very different lever system from rising off the stomach. The 3 curves divide that work: the cervical curve balances the head over the trunk, the thoracic curve organizes the rib cage and upper body, and the lumbar curve positions the pelvis and trunk over the hips. Without those 3 curves, the book states, the body must recruit more muscles, stabilize more joints and control more shear before it completes the same movement. The Creatrix guide to what a neutral spine looks like covers the adult target in standing posture.
Chapter 2 states that spinal development is progressive rather than automatic, and it lists 14 stages in order: lifting the head, rolling, pushing up, crawling, sitting, pulling to stand, walking, running, climbing, squatting, reaching, falling, recovering and repeating. Each of the 14 stages teaches the nervous system to organize 6 regions against gravity: the head, rib cage, pelvis, spine, hips and legs. The book calls these movements developmental instructions for the spine rather than random childhood activities.
| Input | What the book says it builds |
|---|---|
| Lifting the head | The start of the cervical curve |
| Crawling | Coordinated support across the spine, shoulders, hips and core |
| Standing, walking, climbing, squatting, running | The lumbar curve |
| Climbing, hanging, squatting, ground play | Posture, balance, coordination and spinal control |
The book also lists 3 relationships the stages train in the trunk: the head learns to balance over the trunk, the rib cage learns to stack over the pelvis, and the pelvis learns to organize over the hips. The book states that a child lying on the ground, pushing up, crawling, climbing, rolling and getting back up is doing more than playing: the child is training the spine to respond to gravity and building the curves, control and coordination that later support sitting, lifting, running, pushing and working.
During approximately the first 18 years, the book states, the vertebrae are developing in size through ossification, the nervous system is learning movement patterns, and the body is progressing toward the mature adult S-shape. By maturity, typically around age 18, the vertebral structures have largely ossified and the postural pattern is established. The book's conclusion is that every child is in an 18-year spinal training program whether anyone is managing it or not.
The book notes that society tracks at least 7 measures of a child, height, weight, grades, vision, dental health, sports performance and vaccination schedule, but rarely tracks whether the child is developing the 3 spinal curves. Its youth screening list documents 7 items: forward-head posture, a flattened lumbar curve, excessive rounding, limited extension, chronic hamstring tightness, repeated back pain, and compensation patterns during movement. The stated purpose of the 7-item screen is to identify which children need better spinal support before sports loading magnifies the problem; the book adds that the goal is not to label children as damaged.
Chapter 2 lists 9 passive supports that now fill a child's day: car seats, strollers, bouncy chairs, school desks, couches, gaming chairs, tablets, phones and screens. It names 3 supports as necessary, the car seat, the school chair and a teenager's computer, and states that the change is passive support replacing active development. Sitting with the pelvis tucked, the low back flattened, the shoulders rounded and the head forward is the position the book says the body then adopts as its normal posture.
3 more inputs work against the curves in the book's account. Screens below eye level pull the head forward on the neck from early childhood. Heavy backpacks carried with a forward lean train the body to stabilize by bracing rather than by curve. Early sport specialization adds repetitive load to the spine before its structure is developed. By the time a young adult enters the workforce at 18 to 25 years of age, the book estimates that the person may have spent 12 to 18 years of schooling sitting 6 to 8 hours per day, plus thousands of hours looking down at phones and devices. The book adds that change after adulthood is still possible, and that the earliest years offer the greatest opportunity.
The book's rule is that the posture a child practices most becomes the posture the body returns to under fatigue: "Under fatigue, the body does not choose the best posture. It chooses the most practiced posture." It names 6 conditions where that default shows: tiredness, distraction, stress, carrying a backpack, looking at a screen, or entering sports. An instruction to sit up straight, the book states, changes posture for a few seconds but does not change the spinal structure practiced for years.
Chapter 2 also gives the mechanism for permanence: when developing spinal tissue, particularly the articular surfaces and facets, is repeatedly strained, the body shifts posture to reduce load on the strained structures. If the strain repeats, the structure never fully recovers, or the same posture continues, the forward posture becomes the new established neutral and the nervous system accepts it as normal. The book's estimate is that an adult posture program asks the nervous system to override a pattern it has treated as normal for 15 or 20 years.
The adult result the book describes is a worker who arrives already compensating: hamstrings chronically tight because the body uses them to keep the trunk from falling forward, overworked neck extensors, under-recruited deep postural stabilizers, and flattened or reversed lumbar curves. For children, its prescription is daily practice of 11 positions and activities that build the S-shape: ground play, crawling patterns, climbing, hanging, squatting, running, jumping, balance challenges, extension work, spinal control and posture training. The book gives no age-specific reps or minutes for these 11 inputs.
The book describes the lifespan as an arc: C-shape in infancy, S-shape in adulthood, and a drift back toward a flexed C-shape with age, accumulated strain, injury and loss of curve integrity. Its term for daily resistance to that drift is spinal hygiene: preserving the curves, maintaining movement, and reducing the compensation patterns that accelerate decline. For adults, the 5-step system starts with Back Trac rolling; Step 2, the Pelvic Tilt, builds lower-back stability and corrective alignment; Step 3, the Sit-Up over the PowerCushion, restores the lumbar curve; Step 4, Neck Flexion, restores the cervical curve; and Step 5 is the Spinal Twist before supported rest on the rolls, capped at 18 to 20 minutes.
Chapter 11 sets these stop signs as a universal rule across its 3 standards, Desk, Driver and Warehouse: new numbness or tingling, radiating symptoms, weakness, bowel or bladder changes, or sharp escalating pain. When any of them appears, the instruction is to pause training and escalate to medical evaluation.
The Back Trac roller is Step 1 of the system, and the PowerCushion is the fulcrum for Steps 2 and 3.
Practitioner Eileen Durfee, NBS (Nutritional Balancing Science), NASM-CPT — wellness educator, inventor, author, and a Nationally Certified Spinal Fitness Specialist.
Dr. John Scherger was my chiropractor and my mentor, and he also took x-rays of my children. In my book I wrote that he "was the first person to show me that the human body operates according to mechanical laws—that it is not random, but governed by principles that can be understood, measured, and improved."
Our Facebook group is free to join for questions about any of the 5 steps in the Spinal Fitness system.
The book states that infants begin life with a more C-shaped spinal posture, which is normal for early development. The adult cervical, thoracic and lumbar curves develop through movement, gravity and growth.
The book states that the neck curve begins to develop as the child lifts the head. The lumbar curve follows as the child stands, walks, climbs, squats and runs.
Approximately the first 18 years of life, while the vertebrae ossify. The book reports Dr. Scherger's figure of approximately 25% of the human lifespan.
The book states that the instruction works for a few seconds but does not change the structure the body has practiced; its answer is daily movement that builds the curves.
7 items: forward-head posture, a flattened lumbar curve, excessive rounding, limited extension, chronic hamstring tightness, repeated back pain, and compensation patterns during movement.
Published October 14, 2026 • Updated October 14, 2026
By Eileen Durfee, Nationally Certified Spinal Fitness Specialist, NASM-CPT, and author of the Spinal Fitness book.
More from Eileen Durfee
Eileen's free guide, Is Your Posture Aging You?, on EileenDurfee.com
This article is for educational purposes only. These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure or prevent any disease. Nuco Enterprise Solutions LLC.
