Standing still against a force from the front, improper posture reads better on paper; moving into that force, the book shows proper posture winning
Chapter 5 of the Spinal Fitness book reports a result from Dr. John Scherger's contact analysis that it calls one of the easiest to misunderstand: in a single upright, static position resisting anterior force, improper posture required 282 pounds of effort against 776 pounds for proper posture. The book's position is that the static test of posture answers the wrong question.
Chapter 5 sets up the comparison with both postures upright and resisting a force from the front. In that single static position, Scherger's analysis found lower effort and lower shear for the improper posture:
| Upright static position | Force of effort | Shear forces created | Compressive forces created |
|---|---|---|---|
| Proper neutral spinal posture | 776 lb | 1,584 lb | 4,687 lb |
| Improper neutral spinal posture | 282 lb | 36 lb | 2,166 lb |
The book states that at first glance these numbers seem to favor improper posture, and that this conclusion is wrong. The static figures are published in the book to show why the model must not be oversimplified, not as evidence that a flattened spine performs better.
Chapter 5 gives the reason in 1 sentence: contact sports, pushing, bracing and real force production are not about standing upright and fighting motionless; they are about developing momentum and power to move the resistance backward. Its test is not whose posture looks better standing upright, but who can move through range of motion into greater strength and stability.
The book describes the 2 postures under that test. Improper posture may preserve its best stability by staying upright, but if it moves the trunk forward, it moves into instability. Proper posture can move forward through a range of motion and into greater mechanical advantage. The book's summary: "Improper posture protects itself by avoiding motion. Proper posture gains advantage through motion."
Chapter 5 applies the same reading to workers. A person with improper spinal structure may feel safer staying upright because that position gives the only stability they can access, and staying upright also limits forward drive. A worker who avoids leaning into a push, lifting from the hips or generating full trunk drive, Chapter 5 states, has learned that forward motion creates instability.
The comparison the book uses as decisive puts each posture in its best mechanical advantage position for resisting a force from the front:
| Best position against anterior resistance | Total force of effort | Compression forces created |
|---|---|---|
| Improper posture | 282 lb | 2,166 lb |
| Proper posture | 77 lb | 1,218 lb |
That gives proper posture a 3.5-to-1 mechanical advantage in total effort and approximately a 1.8-to-1 advantage in compression forces created. The book's reading is that proper posture can overpower improper posture even when the improper posture appears stable while standing upright, because proper posture can move forward into its strongest position and improper posture cannot.
Chapter 3 attaches a rule to these figures under the heading Do Not Mix the Models: this anterior-resistance model, used for football contact, cart pushing and patient handling, is separate from the broad proper-versus-improper model that compares 77 pounds with 1,166 pounds of total effort.
Chapter 5 defines effective momentum as the ability to move forward against resistance while the spine becomes more stable, not less stable. As the lordotic curves move toward anterior resistance, the combined force of body weight and muscular effort can be directed into the joints as compression, so the joint becomes more stable as the movement proceeds. The book's line: "In proper structure, the body can get stronger as it moves into force."
A C-shaped spine does not have that advantage. When a C-shaped structure moves toward anterior resistance, Chapter 5 states, the resultant force is more likely to be directed as shear across the joint surfaces rather than compression into them, so stability decreases as effort increases. The book names 5 settings for effective momentum: a lineman driving into contact, a worker pushing a loaded cart, a nurse repositioning a patient, a laborer lifting from the floor and pressing forward, and an athlete throwing, striking or changing direction.
Chapter 5 traces a good push from the ground up: the feet press into the floor, the legs transmit force, the pelvis organizes the trunk, the spine transfers force, and the arms deliver the force into the cart. When the spine is neutral and the worker leans from the ankles as 1 stacked unit, the force travels efficiently into the load. When the spine rounds, the shoulders reach forward and the head juts out, Chapter 1 states, the spine becomes the bending point and shear rises sharply at L5-S1.
Chapter 5 summarizes the push in 2 sentences: "A stacked body transfers force. A collapsed body absorbs it." It adds that conventional guidance on handle height and load weight is useful but incomplete, because the missing element is the worker's structure.
The book's Clinical Insight for Chapter 5 states that when a person cannot lean forward into resistance without collapsing, rounding, bracing or pain, the issue is not only strength; it may be a loss of effective momentum. Training should not force more load on poor structure. It should restore the spinal curves, improve pelvic control, rebuild segmental stability, and then progressively teach the body to transfer force again.
Its Trainer Application gives 6 questions for reading the force path:
Chapter 1 records that by the year 2000, Dr. Scherger and the New England Patriots' medical training team were using the sit-up, the pelvic tilt and the Power Cushion in the team's medical training room, and that by 2002 those tools had moved into the weight room for conditioning.
Pain, numbness, tingling and dizziness are the stop signs in the Spinal Fitness book. When one appears, stop the exercise, get evaluated, and then proceed with a therapeutic exercise program designed by a Spinal Fitness expert. The book's training rule for every step is that strain is acceptable and pain is not.
The PowerCushion is the fulcrum for the Sit-Up and the Pelvic Tilt, and the Back Trac roller is Step 1 of the 5-step system.
Practitioner Eileen Durfee, NBS (Nutritional Balancing Science), NASM-CPT - wellness educator, inventor, author, and a Nationally Certified Spinal Fitness Specialist.
The Sit-Up chapter of my book carries 2 photos: me coaching Nick Diaz through the Sit-Up Over the PowerCushion, and me demonstrating the advanced loaded variation. Chapter 5 uses the Sit-Up, Step 3, as the first demonstration of effective momentum in the supine body.
Our Facebook group is free to join for questions about any of the 5 steps in the Spinal Fitness system.
Only in 1 upright, static position: 282 pounds against 776. Through range of motion, proper posture needs 77 pounds against 282.
The ability to move forward against resistance while the spine becomes more stable, which the book attributes to the S-shaped spine directing force into compression.
The book states that when it moves toward anterior resistance, the resultant force is more likely to become shear across the joint surfaces, so stability decreases as effort increases.
No. The book keeps the anterior-resistance model separate from its broad proper-versus-improper model under the heading Do Not Mix the Models.
The book traces force from the ground through the legs, pelvis and spine into the cart, and states that a stacked body transfers force while a collapsed body absorbs it.
Published October 25, 2026 - Updated October 25, 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
