Human Posture and Car-Seat

DesignA Driver’s Guide to avoiding back and neck pain

A Driver’s ideal posture position

• Bring Seatback forward at 100ᵒ - 110ᵒ

This reduces pressure on the

discs in the lower back.

• Adjust your headrest to

the middle of your head.

This prevents neck fatigue.

• Adjust the seat cushion

so pressure is distributed

evenly along the thigh..

An uneven cushion can cause poor circulation and cause discomfort.

Poor posture in the driver’s seat can cause many back and neck issues including:

•Bulging Discs•Sciatica•Herniated Discs•Arthritis

To reduce your risk of back or neck injury due to driving read the tips listed on the right side of the page.

A Company’s Unique Vision to create a comfortable car seat

NASA studies have shown that the human body is observed to take on a neutral posture when in a weightless environment. This is the position that the body wants to take on naturally.

Unfortunately for most drivers, car seats have historically been designed in a way that forces our bodies into an unnatural position. This actually forces our muscles to work constantly to maintain our position while we drive. Therefore it is no surprise that after several hours of constant work/driving, we can begin to feel extreme fatigue… until now!

Most car seats are not designed to promote good posture.

A new car-seat designed for comfort

Traditional Car Seats leave gaps of support

This forces other parts of the back to compensate

Our new car seat eliminates gaps!

More even load distribution saves the spine

Support from the Pelvis to the Chest

INNOVATION THAT LEAVES YOU FEELING WONDERFUL!

Images provided courtesy of Nissan Corp.

What is the ideal seat position?(Provided by Cornell University: http://ergo.human.cornell.edu/dea3250notes/sitting.html)

•Seat Height - Optimum seat height is controversial. • Traditional Criterion - Seat height should be adjusted to support a knee angle of 90-degrees

to prevent leg swelling. However 75% of leg swelling may be due to low leg muscle activity rather than the seat.

• Minimum Height - should be 15" (38cm) which designs to the 5th percentile of women with 1" heels. The seat should adjust 9" (23cm).

• Fixed Height - should be about 17" (43cm). This is a compromise. A chair that is too high leads to increased pressure at the popliteal fold (underside of knees), decreasing blood circulation and increasing pressure on the nerve. A seat that is too low increases weight on the ischial tuberosities.

•Seat Pan - • Seat Depth - recommended is 16.5" for fixed seats and 14-18.5" for adjustable seats. If the

seat depth is greater than the buttock-popliteal length (fifth percentile woman is at 17") then the user won't be able to use the backrest.

• Seat Pan Contours - Half body weight is supported by an 8% area under the "seat bones" (ischial tuberosities). If the seat is hard and flat the pressures can be 85-100 p.s.i. Seat contouring and cushioning can be used to distribute pressure over a larger area and rotate the pelvis forward the promote better posture.

• Seat Cushioning - recommended thickness at 1.5-2". Cushion should be firmer in back and thicker while less firm and thinner at front. Too much cushioning can cause the body to sink into a chair constraining movement. A soft chair may be comfortable at first, but as the body sinks blood circulation lowers, skin temperature rises in affected areas, and compression under thighs increases. These factors combine to increase discomfort. • Cushion Compressibility - Compressibility is termed indentation load deflection (ILD)

or indentation force deflections (IFD). An ideal combination is a soft top layer (25% ILD) over a firm bottom layer (65% ILD). Increased ratios between the two, greater than 2.6, leads to better quality support.

• Seat Width - around 20 - 22" to accommodate clothed persons. If seat has armrests then elbow to elbow breadth may be more relevant.

• Seat Angle - Positive seat angle helps user to maintain good contact with backrest. For most purposes a 5 - 10 angle is recommended.

More on Ideal Seat position• Armrests - give additional postural support and aid in standing up and sitting down.

Armrests should be padded and engage the fleshy part of the forearm. They should not engage the bony parts of the elbow where sensitive ulnar nerve is close to the surface so a gap of approximately 4" between the armrest and seat back is recommended. Cantilevered elbow rests should be 8-10" above the seat surface height. Armrests should be at least 17.2" apart to exceed thigh breadth of 95th percentile females. Finally, armrests shouldn't limit chair access if it is to be used at a table.

• Backrests -

• Height - higher backrests give better trunk weight support.

• Medium-level backrest - gives full shoulder support (e.G. Car seat, office chair) and may need to be about 26" high to accommodate the 95th percentile man.

• Angle - optimal angle seems to be between 100-110-degrees.