Driving ergonomics

From Trackpedia

This article would deal in detail and depth in the subjects of ergonomics, neuorology and movement, as required for the advanced drivers to know in order to practice good work-out, positioning in the car, comprehend passive safety and use the wheel and pedal appropriately.

Muscles

Our body consumes energy by extracting glucose from compound carbohydrates. This glucose is than transformed into ATP mulecules which are the triggers of muscle-tissue flexation. In response to the streaming of the aformentioned agent, the proteins in the cells of the tissue would expand and retract when the input of "energy" (ATP) is removed. A single muscle is thus enable of "pulling" in a single direction, and a mass of muscles, including "Antagonistic" muscles, are required to turn the limbs in the various possible directions.

The turning of the tissues as limbs move, effects the ability of the whole mass of muscles in applying force. Each limb has a certain "curve" that stands for the torque that limb can apply in any given angle. Our hand, as an example, reaches it's topmost peak of force application, when the elbow is bent in 90 degrees. However, do we need an application of full force? Roughly, we can present "force" and "sensitivity" as antagonistic concepts. Applying more torque requires a greater extract of physical force (more ATP used) and more fatigue and less sensitivity.

I say "roughly", because this is not a completly true trade-off. As we have just said, a muscles ability to be "strong" does not make it's operation easier, but also not nessecarily harder. That would depand on the task at hand. Old car rims were heavy, un-assisted by power, stiff and had to be rotated a lot. Old brake pedals were stiffer and required a lot of force to be applied againt the pressure inside the hydraulic master cylinder. With such hard chores, it would require stronger muscles to excert less fatigue, and sensitivelly is far less needed.

Also, the sensitivity of a muscle is based not directly on the muscle itself, but rather the nervous system of the limb it operates. Forearm muscles are thus considered exceptionally strong, as they control the openning and closing of the fingers, thumb and little finger, which are the most sensitive parts in our body, save the slightly more sensitive lips. This gives the person what is known as a "finer motor skill", allowing to operate writing instrumentation, form shapes our of soft materials and other skills acquired at a young age. Since our modern rims are easier to turn (even when without power-steering, leastways at most speeds), this is the skill we must harness when we rotate the steering, instead of our upper body strength, which is used for a "grosse" motor skill such as weight-lifting.

This advantage is achieved partially mentally: The driver should feel the controls, mainly the steering and shifter, with his fingertips more than the palms (though he should be using both) and make little corrective inputs (such as keeping the wheel stable) by a movement guided by the wrist, not the elbow and certainly not the shoulder joint.

Another important point, slightly aided when the former is kept in mind, is to keep the muscles relaxed and not stiffen your grip on the controls significantly as physical forces act upon it in performance driving. The grip should be just tight enough to keep the wheel controlled. Tighter equalls more fatigue, pursuant result of stress and lack of sensitivity without a noticeable difference in control on the wheel.

When a steering input is due, using one hand is automatically going to result in the above. With one hand, the weight of the hand is working on the wheel, resulting in a downward force (created by gravity) as the wheel is gripped or rotated. A force to be contrased by use of muscles external to the hand, mainly upper body strength and back muscles. By merely keeping the other hand on the wheel, you recieve a certain "balance" or "stabilization" effect, allowing to filter out the effect of the hand's weight.

So, which hand gives the better input? Right or left? This carries little to no importance because it's not that fine a job (unlike writing). The question is brought up by drivers mainly in regards to the direction of the corner? I.E. "pull" the wheel with the inside hand to the turn, or "push" it with the outside hand. Well, we have the definative answer: Neither! In driving, and racing not being least in that field, both hands should be used equally. This filters out the difference between the operations of either the pulling or pushing hand, with the pros and cons of either of the two. The input should this time be made with straight wrists and guided from the elbow.

However, during larger inputs, rarely needed in track-racing (and yet, possible) this equasion does not hold true. Grip the wheel at 9 and-3 and turn it with both hands at the above manner. When you reach an input of 90 degrees and onward, three things happen: First, the inside hand reaches the lowest part of the wheel and is placed in an angle that generates an inconvenient angle to the wrist, forcing part of the palm away from the wheel. The upper hand is brought to the very top of the wheel, which is the furthest point of the wheel from the driver. Also, the hands have little extra leverage into the corner (little below an extra 180 degrees), at a certain point both forearms cross. This does not mean your leverage is fully used (you can turn more) and should therefore not be considered very probelmatic, but it's not very desireabl, particularly not an airbag equipped roadcar.

So, with a larger input, to maintain usage of that finer motor skill and maintain the "homebase" of good car control (I.E. To keep the hands in close proximity to the quarter to three position)', which hand do we use? Some argue to push, some argue to pull. Most people I know, some highly experienced in driving and in the atlethic aspects of it, prefer to pull, but this is does not always hold true. The pulling hand evidentally gives an easier input, but is it nessecarily more sensitive, smooth or percise? That depands on the range of motion. If used in the conventional way of begining the input from the basic stature of quarter to three than it's arguable whether pushing will give a better result, because it gives a steadier wrist in that range of motion.

However, by crossing the hand over before the turn and pull towards the basic position through the corner, we keep away from that part of the wheel and maintain a steady wrist. This way, we can use the more subtle muscles during pulling. By pulling, we apply the force of the biceps (the dual-headed muscle people show off, which stretches the forearm) and the forearm muscles connected to them. This enables a utilization of the fingertips to grip the face of the wheel (rather than holding it's diameter) and turn it with percision. When pushing, the joints of the elbow and wrist remain more firmly positioned, but this is more effective in aspects of torque application (important with very heavy steering) than in sensitivity. Yes, crossing a hand over is not ideal, but it's nothing bad (it actually requires less stretching than reaching the top of the wheel) and is done for a small period of time before the corner and at corner exit, rather than maintained mid-corner.

This brings us to the next point, the angles required at the joints, beginning from the elbow. I often see road drivers, or ameatures about to first board a track, position themselves in a position that they find "sporty", perhaps in illusionary impression from open-wheel leagues such as Formula-1. Anyhow, they reach a situation of very outstretched arms and elbows that straighten-up to an angle of 180 degrees all to easily. Why do I bother mentioning this? Because by straightening the limb (hands or legs) we render the motion of it into an a movement in an up-down axis of the joint. By trying to excert that extra bit of leverage with the now straight arm, the elbow would move upwards and "lock". In driving, this is common due to panic in an emergency or crash (or simply a fast kink on the track).

In this position, all the muscles inside the limb are completly outstretched, creating a constant application of a formidibble effort, losing stamina and sensitivity. This can also be viewed as a forward motion of the shoulders and upper back when the hand is locked, or as a forward motion of the buttocks when the leg is outstretched, moving it away from the back of the seat and losing stability. Try riding a bike while straightening out your legs or, on second thought, don't try it.

The second disability of such a posture, is that in a crash or perhaps even riding over a serious bump, would generate a force that will push the body and thus seek to bend the limbs. Flexible muscles can get along with this forward motion, but when the resistance arises from the joint of the bone, it will result in the joint suffering from fracture where it should have simply folded. Also, the fully outstretched muscles will be unable to share the force of impact, transmitting it along the bone, inflicting serious neurolgical and orthopedic damage to the whole limb and perhaps transmitting it to the back, resulting in fracture.

Another important joint, and quite different from the elbow, is the wrist. The main difference between the two revolves around size. The wrist is almost too little to host the nerves and blood-vessles running through it in what is called "the Carpal tunnel". As such, wrist movements, particularly upwards, would pressurize this tunnel and limit the feel at certain regions of the palm. This is in fact more important to take care for when gripping the wheel on the straight, than when turning it in a corner. Gripping the wheel in a sustaine manner with a bent wrist will harm your sensitivity, but moving it when turning the wheel or shifting gear might actually indicate the use of a finer motor skill.

Back

Our back is consisted from the spine (duh!), the nerves wrapped around it and the muscles holding it. This reminds me of one wierd Persian custom of manners: Being unfavorable to seating with their backs turned to one another, even at a restaurant, one of the dinners would excuse the other for seating with back towards saying that "a flower has no belly and back". Well, this anecdote has some truth to it. Back muscles are in fact tissues stretched over the spine to hold it afoot. They are thus dependant on the strength of the parallel muscles in front, like the abs for the lower back and the Trapezus muscles for the upper back. Hence, the lower back is slightly curved (abs are far less durable muscles than the upper-body ones). This little "crater" in the back requires certain support, which all stock seats supply to a certain degree and some may even offer to adjust the amount of lumbar support.

Our back, to be clear ends with our shoulder blade bone, or Scapula, which stems from the collar bone and ends in the Shoulder blade. When you check you distance from the wheel, you should see that the shoulder blades remain against the seat at all times. A lack of contact, and thus a lack of support, between the back and backrest could result in a lordosis which is a curvture of the back. Additionally, it would make the driver less stable in his seat and force him to brace himself by leaning against the steering. We have talked about not having the weight of the hands work on the wheel, but when the weight of a great part of our body is leaned over the steering you practically lose control of the wheel. Trying to turn it with your hands would set you out of balance and you grip on it is tightened significantly.

The problem is that our back muscles, in the manner I described them earlier, are too feeble to cope with the forces working on the body during driving. This creates back aches and makes the back move laterally or forward and away from the seat. The ways to control this are multiple: Make sure the back and seat are in full contact. Increase friction between them with better seats. Maintain that friction through side-support and belts or harnesses, but another basic manner to do this is to use the left foot and the designated "rest-pedal" it has for it near the clutch. You are probably wondering what's up with that.

By placing your foot onto the rest pedal you have opened the gap between your legs. Placing the legs in a wider, symettrical "V" formation, increases body support (especially of you get the knees or thighs to contact the console and/or door of the car. Additionally, this makes the weight of the lower parts of the back rest evenly on both seating bones (both parts of your ass) and removes lower back aches, usually inflicted to people with the left foot hovering over the clutch or brakes. Left foot braking, is hence unrecommended without proper harnesses and buckets.

We call it "rest-pedal" over "footrest" for a reason: It is a pedal. It's goal is to brace the body in action. I.E. During a tight, high G-force turn, the driver can apply pressure with his left foot against the rest-pedal and lean on it, rather than on the right foot pressing the brake (or gas) or over the hands operating the wheel. The same applies with hard braking, and gives the additional benefit or having both feet apply pressure simultanously, allowing to apply more brake pressure faster, all while still being able to control the steering wheel. The rule "both feet in" for pressing the brakes and clutch during emergency braking, must thus be corrected into pressing the brake and only once you have rolled unto it, pressing on the clutch. Lift both feet in the air and your ability to kick back at the pedals will be largely reduced.

Damage via accident

During an accident, damage can be inflicted on the human organism via one or more of the following two reasons: Sudden involuntary movement or impact with a solid object.

• Sudden involuntary movement is the result of a sudden G-force experienced during a crash. Such forces will normally be stronger than those experienced during a manouver, and also build up more suddenly. This force working on the body will take it's toll on muscles (if you race, you neck knows what I mean) and on the skeleton. In a strong collision (anything above a velocity of 35 km/h) the movement can force a certain free limb to move in an unnatural manner all too fast and too much, resulting in fracture that can also radiate a shock through the bones, or puncture blood vessels and internals organs with shards of bone.

We all probably experienced that, when going to stairs, if you slip, you lean your weight to balance yourself, but than as the weight of your whole body is loaded suddenly unto the joint of the ankle, it twists it painfully. In driving, the same phenomenon is experienced in the neck (A "whiplash" when the neck is rocked backwards without support of a head-restraint) or in the arms and legs if they are straight: The instinct of fear makes the driver push himself away and into the seat, locking his limbs and than when the sudden load on the hands in the crash seeks to fold them, they break rather than fold (as they would if they were bent in the elbow) and the bone -- unsupported by the muscles -- tends to radiate the shock towards the shoulder and scapulas. Drivers who lean forward from the seat would experience similar injuries to their back as it is catapulted backwards. Similar injuries are inflicted on fingers if the wheel suddenly jerks.

• An impact with a solid object usually means hitting the under-dash with the lower parts of the body, crushing it. Hitting the wheel or inflating airbag with the chest, Being pierced by an un-collpasable steering column; hands and head, hitting the windscreen, semi-opened visor or ceiling with the head, hitting another passenger. An unattended luggage or object in car hitting someone, etcetra.

Certain measures used as "passive" safety installments, are used to help minimze the injury from both origins. The shock is reduced mainly by two things: The seat and the crumple zones. The seat of the car is actually a splendid creation of arthopedical design, intended to offer no back injury during a long ride, sudden manouver or crash. With the back straight and against the seat, no serious back injury is expected. Of course, this requires the driver to be positioned in the seat with his back and buttocks firmly set against it, and with no need to straighten-out any limb and/or reach out any part of the back when operating the controls. Modern seats in new, luxorious cars, have additional safety features like self-adjusted side support by pressurizing a given portion of the seat according to the direction of the G-force, a backrest that automatically collapses and tilts backwards to offer better support to the back and fully absorb the shock instead of it, head-restraints that automatically engage behind the drivers head, a seat that automatically tilts backwards, etcetra.

Crumple zones are a bit more complex than the seat. Very old cars were stiff in structure and while this could, in very harsh crashes, avoid an injury of the second form (I.E. hitting a part of the hitting object protruding through your car or being squeezed inside your car), crumple zones offer ideal protection against the far more common internal injuries inflicted by a crash. The external parts of the car are being constructed from padded and elastic parts of metal or plastic (for sake of endurance, as plastic and deform and than be restored to it's original shape without much wear as metal) which are intentionally meant to crumple at given zones and thus absorb more and more of the shock, while diverting it away from the inside of the car, supported by a certain form of a "roll cage". Crumple zones include the following:

• Collapsable engine: Engine compartments built to collapse and be moved down or back towards a pre-designated spot. The gas line is also collapsable to avoid the car being set aflame.
• Collapsable trunk: A very large crumple zone in the bumper. With small cars with a short trunk, this crumple zone is less effective when the velocity increases and that is why accidents where a person stops on the hard shoulder and gets hit by an oncoming car are usualy fatal. Cars are not supposed to absorb a hit in a velocity of 100km/h from behind and tend to squeeze. However, during a sudden stop, always prefer the hit from behind over the hit in front. The chance of it is smaller, the damage and risk are categorilly lower and the strong pressure on the brake pedal allows the car's crumple zones to absorb the impact instead of being tossed forward, risking a whiplash.
• Collapsable B beams: In a side-collision, the damage is inflicted away from the doors to that the impact will not crush the side of the vehicle's occupants, with particular reference to the driver's palm. The damage is directed towards the back side of the front doors, the front and rear wings, the B-beams and away from the mid-height portion and front parts of the doors, at which point the doorskin is closer to the bodies of the occupants of the car. Those portions are protected by rods inserted into them.
• Collpasable steering column: Old steering columns would protrude through the humb of the wheel and stab the driver. Modern columns fall or break in their mid-section.
• Collapsable interior mirror: Modern interior mirrors are placed partially or fully from the windscreen rather than the ceiling of the car. The mirror is made with a small crumple zone at that point, which makes it fall off without the risk of it: a) causing damage to someone's head. b) Hitting someone's head or hitting one of the airbags when stationary and unhindered. c) break into shards of glass that can create cuts, or into small shards that hurt the eyes and face ("Spider-nets", as paramedics call the form of such fractured glass).
• Collpasable backrest tilt: In a severe crash, this helps the backrest absorb the rearwards movement of the back and avoid pressure over the head during a rollover. This is also why no one should install a bucket/recaro seat without roll protection.

When referring to impact with a solid object, the means of safety are primarily seatbelts. The seatbelt is a two or three-point harnesses (with more points being rulled out for motives of price, comfort and problem with hooking and unhooking them, on a normal drive or after a crash) and are the only means of preventing death when 35km/h are exceeded. Stories of such belts causing death in a sinking or burning car are greatly myths! Like with crumple zones and the protection offer by the seat, we can take active steps to improve the seatbelt's effectiveness, by tightening it around our waist or putting it on with the seat drawn back, holding it and than moving the seat forward to tighten it up (the second option used when you go racing). We must also place the seat in a good positioning, and with the backrest relativelly erected and the seat tilted backwards if possible, to reduce the chance of any part of our body "diving" somewhat under the belt.

The seatbelt's main job is to make sure the lower parts of the body (hips, pelvic, abodomen) are left unhindered. The risk of being catapulted through the windscreen is normally not justified. The seatbelt is supported by two mechanisms:

• Airbags: Cushion the hit of the upper body towards the steering, door or even protecting the knees from the under-dash. An airbag is deployed by an electric signal originating from motion sensorts that sense when the car is decelerating substantially faster than it's brakes allow. The electric signal initiates a chemical response that detonates an explosive into a chamber of gas, creating a jet that inflates the bag through a collapable portion of plastic in the car's body or seat. Within a range of 24.5 cm (with an American driver's airbag), the airbag reaches full inflation and the gas disperses via the semi-punctured bag, giving it the starched smell and the cushion.

Unless belted and well-positioned, a driver can be hurt by the airbag during it's initial inflation. The velocity of that inflation is in a speed of little over 350km/h, plus the opposite velocity of the body being thrown towards it at at least 50km/h.

• Pretensioners: A similar device that tenses the belt unto the driver's body before the actual crash.