Drivers Beware:
Lumbar Support Can Be Harmful To Your Health!

 

YogaBack Posture: The Key to Faster Reaction Times Driving

by Dennis Zacharkow, PT
© 2014

Fast reaction times at the foot pedals and steering wheel are more important today than ever before, with the dramatic increase in distracted driving from cell phone use and texting -- besides other pre-technology distractions such as eating, drinking, and smoking.

As evident from many television commercials, the auto industry continues to promote a passive, lounging driving posture with an excessive backrest recline. (An excessive backrest recline of 25 degrees is also the basis for the flawed, forward headrest design of the last few years. See the article entitled "New Car Headrests (Head Restraints) Designed Too Far Forward.")

Driving in a lounging posture results in a relaxed core, with the driver having the trunk muscle activity of an unconscious person. Such a driving posture also unbalances the body, with the center of gravity of the trunk displaced behind the pelvis (Mosher, 1899). This distorts the proper upright relationship of the head, neck, rib cage, and pelvis, and it leads to fidgeting, impaired diaphragmatic breathing, and fatigue.

A relaxed core and unbalanced body can both result in delayed reaction times at the foot pedals and steering wheel.

The driver's seat is not an easy chair for lounging, but a special "work-chair," with the driver being involved in a continuous vigilance task (Grandjean, 1980). This requires a very stable and alert driving posture.

The key to faster reaction times driving is transforming one's driving posture from a passive to an "active-alert" posture. This involves activating the elongation reflex of the trunk, resulting in optimal trunk stabilization through proper activation of the diaphragm, transversus abdominis, pelvic floor muscles, and the lower thoracic erector spinae (Rathbone and Hunt, 1965; Zacharkow, 2001).

An activated core through proper trunk stabilization is essential for providing an effective foundation for all limb movements (Evans, 1985). The end result is faster reaction times of the right lower extremity at the foot pedals and the upper extremities at the steering wheel.

Specific features of the driver's workspace essential for an elongated driving posture and the fastest reaction times are:

  1. A slight backrest recline of 5 degrees to 10 degrees.
  2. Sacral support to stabilize the pelvis from the vibration and road shock, resulting from the interaction of the vehicle with the road surface (Zacharkow, 2001). Sacral support also provides counter-support for the pressure applied by the foot to the foot pedals.
  3. Lower thoracic support elevates and stabilizes the rib cage, thereby correcting the typical slumped driving posture. Lower thoracic support reduces fatigue by optimizing diaphragmatic breathing and inhibiting shallow, upper chest breathing (Zacharkow, 2001). In addition, lower thoracic support provides counter-support for the pressure applied by the upper extremities when steering.
  4. A stationary inclined footrest, located to the left side of the brake pedal, enables the left lower extremity to exert effective counter-pressure for preventing the forward migration of the pelvis on the seat (Evans, 1985; Zacharkow, 1988).
  5. Hand positions at the side of the steering wheel (approximately 9 o-clock and 3 o'clock) result in the fastest reaction times at the steering wheel.
    Hand positions at the top of the steering wheel result in an elevated arm posture leading to fatigue and excessive tension in the neck and upper back. This is an unstable hand position for fast reaction times, as the driver tends to be hanging onto the steering wheel, rather than controlling it (Barker, 1985).
    Hand positions at the bottom of the steering wheel can further relax the neck and upper back -- but the upper extremities are at a poor mechanical advantage for fast turning of the steering wheel.

References

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