How to Modify Your Car Seat For a Pain-Free Ride
Most of us spend a good deal of time in our cars, commuting, chauffeuring kids around, doing errands, or if we’re lucky, heading out to an adventure spot. Much of this time is spent being physically uncomfortable, especially if the car was manufactured in the last decade. There seems to be a downward spiral of poor posture and design that reflects poor posture - which in turn worsens posture. How can we break this cycle?
The industry standard for human form reflects the average in society: shoulders forward, S-shaped spine, and forward head. Car seats are designed to fit these features.
A checklist for healthy posture when driving includes:
- Shoulders: back and down
- Neck: elongated and stacked over the spine
- Bottom: well back in the seat
- Spine: elongated and well-stacked
Modern car seats often make these simple posture practices challenging or impossible. The good news is that it’s relatively easy to fix almost any kind of carseat to make it conducive to good posture.
- Shoulder positioning. You may find that the “bolsters” in your carseat get in the way of placing your shoulders back.
The bolsters add considerable horizontal curve to this seat upright, and prevent the arms and shoulders from resting back beside the torso.
The origin of bolsters lies in the racing car industry - bolsters keep racing car drivers in their seats as they whizz around corners at high speeds. For those of us not compelled to turn corners at 100 mph, the bolsters are an annoyance that make it impossible to set the shoulders in a comfortable and healthy place. Solution: Build up the backrest area between the bolsters, so your torso is no longer sunk between the bolsters with your shoulders forced forward. Depending on how much your car’s bolsters protrude, a towel folded over a couple of times may suffice, or you may need a much thicker support. When I travel, I use rental cars. With each rental car, my first action is to profile it: will a single Stretchsit cushion suffice or will it need additional thickness? Technique: After adding some thickness to the mid-portion of the chair upright, move one shoulder at a time a little forward, a little up, and then significantly back and down. Once you have your shoulders back in place, you may discover you need to move your seat closer to the steering wheel to comfortably hold the steering wheel. Be sure to keep a safe distance from the airbag.
- Neck support. Have you noticed that many car headrests push your head forward uncomfortably? The degree seems to get worse with the years. Headrests now have a new official name, which is “head restraint.” They are shaped to stick far enough out that the head is resting against the headrest and would not have any space in which to whip backward in the event of a collision.
The head restraint, as headrests are now named, reflect, and perpetuate, forward head posture.
The standard that determines the extent to which the head restraint juts forward is the Crash Test Dummy. The Crash Test Dummy was modeled on a person with typical Forward Head Posture, and therein lies the rub.
The Crash Test Dummy has forward head posture
When I taught a workshop to the designers at Johnson Controls in Ann Arbor, they pointed to my Stretchsit cushion and remarked “the reason your products are popular is that we’re legally obliged to design seats the way we do.” It is sad when designers become constrained by deterioration in people's posture.
Forward head posture is now so common it negatively influences car headrest design.
Solution: Very similar to the solution for bolsters, but the extent of how much you build up the central portion of the backrest now depends on how much the head restraint juts forward. DO NOT turn the headrest around 180 degrees or remove it or sit forward in your seat - in case of an accident, this would put you at risk of severe damage from whiplash. Technique: Determine the best posture you are able to assume in your neck. Now pad the central portion of the backrest so that the headrest works to rest your head against. Elongate your neck in any of the five ways described in 8 Steps to a Pain-Free Back, and “hook” the back of your head against the headrest so your neck is getting a gentle stretch.
- Setting the bottom back in the seat. This is not a problem in most cars. Some notable exceptions are:
- very old cars whose seats have worn down so your bottom sinks into a “cave.”
Some carseats wear out in ways that create a "cave" for your bottom to sink into.
Solution: build up the cave to horizontal or near horizontal. Do not build it up to be a wedge - wedges are helpful for stacksitting, but not for stretchsitting, and in a car you want to stretchsit, not stacksit.
- Bucket seats: Ouch. Solution: It’s very difficult to fix these. I recommend starting from scratch - go to Relax the Back, buy a seat to place in your bucket seat, and modify as needed.
Bucket seats are very difficult to modify so they support healthy posture
- Spine support. Does your car seat have lumbar support? This is based on conventional wisdom about an S-shaped spine being normal and healthy.
An unhealthy amount of built-in lumbar support in a carseat.
My experience is that it causes extra curvature in the spine, tight back muscles, degenerated discs, and arthritic changes in the vertebrae. Solution: What you really need is a thoracic support that you can stretch your back against. Technique: Use a Stretchsit cushion (if you have a fabric seat, a folded towel can also provide the grip you need) suspended behind your mid-back. Follow the instructions in 8 Steps to a Pain-Free Back to stretchsit and put your lower back into a gentle, comfortable amount of traction.
So what can you do to set your car up for healthy posture?
- If you're in the market for buying a car, examine the carseat. Some brands are better than average in the design of their seats. The Fiat 500, for example, has a head rest that works with healthy neck posture, and has bolsters that do not extend all the way up shoulder level.
The Fiat 500 is an example of car model that has a relatively well-designed carseat.
- The Stretchsit cushion is remarkably effective in mitigating a lot of flaws in carseat design. It can neutralize the effects of exaggerated lumbar support, deep bolsters, and head restraints that jut forward too far. In addition, it facilitates stretchsitting, which is healthful in itself, but also dampens the effect of bumps and jolts in driving, especially on bumpy roads.
The Stretchsit cushion helps transform poor carseats into healthy carseats.
- Set yourself up with good posture. No matter how good your carseat is, there is no substitute for knowing what to do in your own body. Stretchsitting, which is one of the easiest Gokhale Method techniques, is well suited to driving. Lengthen your spine against a support at the level of your mid-back, roll your shoulders back, elongate your neck against the head rest, and enjoy the ride!
What kind of car do you drive and how well do the seats work to support you? How have you improved your carseat?
I greatly value your
I greatly value your attention to the Head Restraint, but this is only one problem for sitting posture in automotive seats. As a retired Professor and researcher who has studied the human body, sitting posture and seat design for over 50 years, it is appalling to read your quotation from Johnson Controls (today Adient) that they are unable to design seats for good sitting posture because they are legally obligated to bad design. The design of the head restraint is covered by NHTSA 202a from the US Department of Transportation but after the last modification to the Regulation, it is no longer a problem to design for sitting posture. The first version of this regulation required use of a 25 degree back angle, a reclined angle used by slumped postures. In the present version, the back angle in design position can be anything that the vehicle manufacturer specifies which includes an upright seat back angle that would move the head restraint rearwards for people to use for comfort and safety. The problem at the seat supplier is not lack of good engineering, it is lack of appropriate tools that represent sitting postures used by drivers of all body sizes. Unfortunately, many in the seat industry think sitting posture is defined by angles in the legs and arms as represented in some of their tools. However, sitting posture is defined by back, leg and arm joint anbles because back joint angles are used for vision and postural comfort.
Seats designs are built initially for the H-point machine, not the crash test dummy you show. The H-point machine was developed in the late 1950s, adopted by SAE in the 1960s and included as a standard in NHTSA Regulations in 1967-8. This tool represents a slumped posture of an average male with legs of a tall male. The tool was based on x-rays of 12 tall men (greater than 80th percentile stature in the late 1950s) sitting in a bench seat to determine the position of the hip joint (thus, the H-point machine). When NHTSA decided to specify head restraint positions to solve the whiplash problem in rear impact crash events, they attached a Head Restraint Measurement Device (HRMD, for short) to the H-point machine. After many months of "government-industry debate", the regulations was released with a required 25 degree back angle. Since almost no one could sit in these seats, this regulation was modified by NHTSA to allow use of seat back angles less than 25 degrees. SAE developed a new tool in the 1990s to replace this 1950s tool, but NHTSA does not allow use of the new tool to satisfy their Rules and Regulations.
The vehicle manufacturer designates H-point position, seat position for the H-point test, and seat adjustments for the Supplier to create seat prototypes. Each iteration of seat design from the Supplier must pass the H-point test as well as meet the backset requirements for the Head Restraint and provide some measure of comfort when people use the seat to drive the new car. This process is over 50 years old and does not use a tool that represents seated postures to design seat shape for safety, comfort and ergonomics.
In the course of developing the shape of these seat prototypes, seat suppliers should carefully design the seat for people of all body sizes to sit in their preferred back postures. To accommodate the range of variation in drivers for safety, comfort and ergonomics, seat back shape at the biteline (intersection of seat back and cushion) and the seat cushion shape at the nose of the cushion have to accommodate a variety of sitting postures. For those people who want to sit in an erect posture which raises eye height, particularly short drivers, there needs to be sufficient space to accommodate moving the buttocks (pelvis) rearward to a position under the torso in the upright, erect sitting posture. In addition, as you correctly point out, an upright posture not only needs support at the lumbar but also at the chest. Many engineers have a difficult time moving the biteline rearward because they feel that support of the buttocks is desireable for slumped postures that people use with a forward head restraint position.
The second area of concern lies in the shape of the front of cushion. When people sit with an upright back posture, they move the seat closer to the accelerator than when they are sit in a slumped posture. This change is due to pelvic rotation and the corresponding change in position of the hip joint. The pelvis rotates over the ischial tuberosities and changes the position of the hip joint in slumped, neutral and erect postures. As a consequence of this change, the angle of the thigh in upright drivers will move downwards which requires a downward seat cushion tilt adjustment. In a slumped posture, the seat cushion tilt is raised to maintain contact with the thigh thereby preventing the feeling that of sitting on a ledge without any thigh support.
I am writing this message because good posture in driving seats is not simply proper spine and back posture. Sitting requires support of body weight but this support changes from load bearing to simple contact that must correctly accommodated. A math-based, patented tool is available for seat design. It is based on digital human body models that represent the deflected shape of soft tissue and the positions of skeletal landmarks for seat design. Johnson Controls had a license for this tool but no longer has the tool. The name of the tool is ERL and I was the Principal Investigator (Herbert M. Reynolds) who led the research to develop this tool, You can read about this tool on Slideshare and the ERL website (www.erlllc.com). I have recently written a chapter for a book on Posturography and Digital Human Models that describes the results of an analysis of 41 vehicles with this tool. This book should be published shortly.
I want to wish you well with your Gokhale Method, and I am available to provide any assistance or answers to any questions you might have.
Herbert, Which cars have the
Herbert,
Which cars have the best seats?
thanks
I have a 2016 Toyota Sienna,
I have a 2016 Toyota Sienna, and chronic low back issues, w/ pain. Basically disc degeneration. It goes from L1-S1. I recentlly started a job that has me driving for up to 3 hrs. daily, and no matter what I try, I can't find a position that doesn't worsen the pain. It's sometimes up to 9/10 in severity and throbbing. I know I need to get to a dr., but I'm very interested in any recommendations you may have.