Back Care on Airplanes
Professor Alan Hedge, PhD Director Human Factors and Ergonomics Laboratory Cornell University Department of Design and Environmental Analysis Ithaca, NY http://ergo.human.cornell.edu

In 1999, in the U.S.A. over 500 million passengers traveled by air to domestic and international destinations, and together they traveled over 600 billion miles.1

So far in 2000, the number of travelers is increasing by almost 6 % and the distance traveled by almost 4 %.¹ Load factors have increased and currently are around 70%. Airline travel is a necessary part of life for many people. Airlines also provide jobs for over 640,000 people, over 59,00 of whom are pilots.²   One thing all share, pilots and passengers alike, is that flying is a predominantly sedentary activity, and sustained sedentary postures can increase the risks of back
problems. This article outlines important health considerations and provides information to help you improve your comfort when flying.

Class Distinctions: First and Business Class

With first class and business class fares yielding higher profit margins than coach class fares, many airlines have implemented programs that are upgrading the quality of accommodation in these cabins, especially on long haul flights. In addition to higher quality in-flight service, more sumptuous seating is being provided. For the price of a first class ticket on international carriers, you have more than ample leg room and a seat that effectively reclines into a bed.

Many airlines are also focusing on the daytime business traveler, and they are now providing seats with ample space that allow the mobile warrior to power and use a laptop computer in relative comfort.
 

Class Distinctions: Coach Class

The vast majority of travelers are not able to experience first or business class seating. For these users, the coach class cabin is their temporary home for the duration of the flight. Many aircraft currently in service were designed and built over 10 years ago, and often well before the invention of devices such as laptop computers. The popular Boeing 737 began commercial service as the 737-100 in Europe back in 1968. That same year the 737-200 began service in the U.S.A.  The latest member of the 737 family, the 737-900, was introduced in the summer of 2000.
 

Human factors designer recommendations for comfortable airplane seats have been published (see diagram).³ According to these guidelines an airplane seat should have at least  the following dimensions and features:

• a 5 degree seat-pan pitch with a 105 degree seat-to-back rest angle for normal upright seat position.
• a 45 degree seat recline over a continuous range
• a backrest height of 24 inches to the base of the headrest
• a minimum seat-width clearance of 19 inches between the arm rests
• a seat-pan that automatically adjusts to a horizontal position as the backrest is reclined
• separate 2 inch-wide armrests for side-by-side passengers or one 5.25 inch armrest to be shared by the passengers
• a seat-clearance of 12-13 inches to provide ample leg space
  

How well have airplane designs implemented these minimum recommendations. On some recent flights I measured the seat dimensions to check this out. On a Boeing 737, where I was fortunate to be upgraded to first class, I sat comfortably in a seat with ample leg room, even with a bag underneath the seat in front of me. The seat-width was 19.25 inches, the armrest was shared but was a broad 4 inches, and the seat-clearance was 12.75 inches. I'm an average stature, heavy set, middle-aged man, and in this seat I was ably to easily work with a laptop computer with a 15 inch screen.

Unfortunately, not all airplane seats in coach class are designed to these minimum standards. On my next flight, on an Airbus 319, I had a center seat in coach class and I felt like I was on a cattle truck. The seat-width was 18 inches, which still worked for me, but did not work well for the larger men sitting either side of me, and the three of us jostled for position on the two, 2 inch armrests. With a bag placed under the seat in front I had no room to extend my feet ahead of my knees. The seat-clearance was a meager 8.5 inches, making it impossible to comfortably cross the legs or even access the bag stored beneath the seat in front. When the seat in front of me was reclined and my tray table was down, I had insufficient room to work at my laptop, even with my seat fully reclined. In fact, at an 8 inch distance from my abdomen, which isn't that huge, there was only an 8 inch height clearance, making it impossible to fully open even a small laptop computer. Notwithstanding this, as the following picture shows, some of my fellow passengers valiantly struggled on with attempting to work at their laptops! I decided that in this case it was prudent to abandon hopes of productive work, at least for the 2.5 hours duration of the flight!

Coach passengers struggle to work productively in cramped seating.

Other important demoscopic changes that challenge the design of coach class airplane seats include the fact that, on average, the American public is growing larger and living longer than ever before, so more air travelers are physically bigger and more are older and differently-abled than ever before. Large people need wider seats with greater leg clearance. The office furniture and entertainment industries are responding to this by creating wider chair seats, but with the increased passenger demand the very opposite seems to be happening on many aircraft (though some airlines are changing layouts to give coach passengers an extra few inches seat-clearance). Airplane seats have design features that simply wouldn't be tolerated by people in other settings, for example, seats often have headrests that tip the neck forwards when the seat is upright, they have hard arm rests, they have seat cushions that are too firm, particularly for older travelers, and they lack good lower back support to the lumbar region. 

Tips for Surviving Coach Class Air Travel

For the millions of travelers for whom first class or business class travel isn't an option, here are some tips that will help you to look after your back and make your journey a little more comfortable.

• Use a pillow to support your head and neck. An inflatable air pillow works well, it's compact when deflated, and once inflated you can snooze and avoid waking with a stiff neck.
• Use an airplane pillow or a rolled blanket to make a support for your lower back. Rather than putting this support completely across the back of the seat, which will decrease your seat-clearance, try to use the airplane pillows to either side of your lower back, or try to make an inverted T with them. 
• Keep adequate space under the seat in front of you for your feet. If you have a larger bag, put this in the overhead storage bin. If you have a smaller bag, position this centrally with your feet to either side.
• Keep your feet in front of you at all times, try to stretch out your legs, and keep your feet and legs moving. This will aid circulation and reduce fatigue, as well as decreasing your chances of suffering a potentially fatal blood clot.
• Stand up and move around the airplane as often as possible. On a long-haul flight try to walk the aisle at least every 30 minutes. Choosing an aisle seat will help to make this easier because you will not have to disturb fellow passengers.
• Drink water rather than alcohol, coffee of tea. Flying dehydrates the body because of the very low humidity levels in the pressurized air cabin. Alcohol, tea and coffee are diuretics that also encourage dehydration. Water will re-hydrate the body and help to prevent circulatory problems.

What about the Flight crew?

Passengers may find the seats uncomfortable for the duration of the flight, but what about the flight crew who may have to repeatedly fly the aircraft? A study of middle- and long-distance Qantas pilots found that reports of postural discomfort and low-back pain during flying were widespread.⁴ Researchers noted that this postural discomfort potentially may distract pilots' concentration, which in turn might jeopardize flight safety. To improve comfort, engineers tested the effects of covering the seat with sheepskin, but complaints of postural discomfort were not eliminated. A recent biomechanical analysis of the pilot seats from Boeing 737-300, 747-300, 747-400, McDonnell Douglas DC10 and Airbus A310 compared seat designs with existing human factors and biomechanical standards. Surprisingly, all of these seats failed to meet requirements. Particular design problems included issues of seat-depth and seat pan angle, and inappropriate armrest and lumbar support height and design. The researchers found that none of the seats allowed the pilots to attain a comfortable sitting posture. Specific recommendations were made to improve the design of pilot's seats, and these included:

• increasing the seat depth and reducing seat-pan incline
• raising the height of the lumbar support
• making arm rests height adjustable
• tilting the entire seat to an angle of 7-10 degrees at the ischial tuberosities also known as the 'sit bones' (the bony protuberances under each side of the pelvis that support the body when you sit on a surface).

 Whether or not these recommendations are implemented in future pilot seat designs remains to be seen.

References

1. Air transport Association (http://www.air-transport.org/public/industry/183.asp)

2. Airline Pilots Association International (http://www.alpa.org/)

3. Woodson, W.E., Tillman, B. and Tillman, P. (1992) Human Factors Design Handbook, 2nd ed. New York, McGraw Hill.

4. Lusted, M., Healey, S., Mandrijk, J.A. (1994)  Evaluation of the seating of Qantas flight deck crew. Applied Ergonomics, 25, 275-282.

5. Goossens, R.H.M., Snijders, C.J., Mandrijk, T. (2000)  Biomechanical analysis of the dimensions of pilot seats in civil aircraft. Applied Ergonomics, 31, 9-14.

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