Thought Bytes...
January 2002

This month, "Thought Bytes" and "You Asked for It" are combined as they address the same topic.

Going the Distance

Holidays invariably see me driving to the Okanagan to visit my family. For short visits I fly, but when I stay for more than a few days I usually drive. That way I can take my skis, the cats, presents, etc. I pack my life into the car for an 11 hour drive. Unless it is snowing, the drive is actually fairly relaxing. Too relaxing. I slip an audio-book in the tape player and catch up on my reading. I can go for hours. The problem comes when I have to stop.

Stopping the vehicle isn't the problem. Getting out of it is. After sitting for several hours continuously, my body doesn't like to straighten out. It comes back to the old issue that the human body was not designed to sit. We were designed to hunt and gather, pick berries, throw spears, etc.

Driving, in our society, is fundamental to our sense of freedom. So, how can you reduce the physical effects of driving?

The Mechanics of Sitting in a Car

Sitting on it's own creates strain in the lower back in three main areas: unequal distribution of pressure on the disks in the lumbar spine, stretching the supporting muscles and straining the sacroiliac joints. These strains are compounded by the exposure to vibration and impacts. When we get out of the vehicle, we expect our bodies to recover from these strains in seconds. But that just doesn't happen.

Let's break it down:

• Disk pressure: flexing the spine compresses the anterior of the disk, pushing the contents toward the back. When we stand up, it takes a few minutes for the disk pressure to equilibrate.
• Muscles stretched: the muscles in the lower back "learn" an incorrect length when the back is held in a flexed position. When called to action, the back is more likely to be injured because the muscles are less able to support it.
• Sacroiliac joint strain: The SI joints are not designed for movement. Sitting with the pelvis tilted forward stresses these connectors between the pelvis and the end of the spine. When irritated, the SI joints can put pressure on the Sciatic nerve.
• Vibration: High frequency impacts in passenger vehicles do less damage than in commercial vehicles (where the impacts are at a frequency more closely associated with the resonant frequency of the human trunk). With each impact a bit of fluid is forced from the disk, making you shorter as the trip progresses. Combine this with the unequal distribution of the disk contents and the disk can be considerably weaker. Luckily most of this fluid is recovered when we are at rest.
• Recovery: Long durations and repeated exposures can put the back at risk. Each time the body is not able to recover completely, the risk of injury increases. But how much time is needed? It varies with each person, their injury history and their activity level.

Reduce the Risk!

Start by using good posture in the vehicle.

• Make sure there is enough lumbar support at your lumbar spine! Unless you have a fancy new car with adjustable everything, the lumbar support is probably at the wrong height. I use an Obus Lumbar pad to give me extra support right at my waist where the back naturally curves inward.
• Tilt the backrest back slightly. You don’t need to be reclining, but leaning back in the seat will reduce loading on the disk. This is because you don’t need to use muscles to support the weight of the upper back. It has the added advantage of allowing vibrations to transfer into the seat back, instead of being absorbed by the disks.
• Balance your legs and feet. Your ankles, knees and hips should be at the same level. Of course, you will need to change positions, but make sure that you don’t drive for hours in a poorly balanced position. Put the cruise on so that you are not continuously contracting one set of leg muscles.
• Get your hands down. For long distance driving, your hands should be at 3 and 9 or 4 and 8 on the clock. Keeping them at 2 and 10 is fine for city driving at slower speeds. Honestly, do you want to be able to turn the steering wheel 90o when you are travelling 110 km/hour? Keeping your upper arms against the sides of your body will reduce loading on the neck and shoulder muscles.
• Change positions. Squirming is a good thing (but don’t tell your kids that!). We are creatures of motion. Within safe limits, move your arms, legs and body. Put the cruise on so that you can flex and extend your knees.
• Take breaks. I won’t suggest that you take a 10 minute break for every hour of driving. That would be unrealistic. Ideal, but unrealistic. But, if you drink lots of water you will have to stop about every 2-3 hours. When you do stop, park at the end of the parking lot so you have to walk further.

What to do when you stop

• Take time to recover. Give your body a few minutes to recover before hauling the luggage out of the back. Walk around the vehicle. Walk up the path and back to make sure there are no obstacles to trip over. Say hello to your hosts / pets / plants, whoever. Heavy lifting before your back has recovered adequately can result in serious disk injuries.
• Get the joints moving. Do a couple of stretches. These don’t have to be calisthenics. Try reaching for the sky. Do a simple back extension (see stretches later in this newsletter). Avoid stretches that have you reaching down or otherwise flexing the back - after all, isn’t that what you have been doing for the last few hours?. Stretches that maintain the lumbar curve are great.
• Don’t have a seat! As tempting as it is to sit down to lunch in the diner or flop on the couch with your hosts, spend a couple of hours standing and walking if you can. Consider standing or walking for 10-15 minutes for every hour you have been sitting in the vehicle.

  For some people, driving is something to be endured. For others, an enjoyable experience. As with most things in life, the key is moderation.

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