Bike Fit Symmetry: You're Off-kilter and Twisted and it's okay (sort of)

Let me let you in on a little secret:  you sit funny on your bike.  No really.  We imagine ourselves to rest evenly on the saddle and have our arms and legs meet the bar and pedals in a symmetrical way, but this is likely far from the truth. Our bike fit symmetry? Off-kilter and twisted is a pretty apt description for around 80-90% of us cyclists on our bikes.What do I mean?  How uneven can we be?  The bike is perfectly symmetrical, right?  So our hands are (almost) perfectly even on the bars, and our feet are in equal positions on the pedals (assuming the cleats are adjusted the same on each shoe).But this is exactly the point.  The bike is generally very symmetrical -- if it weren't you'd have a lot of other problems with safety and handling among other things -- and our hands and our feet are mostly placed very symmetrically.  This creates a problem because we are not symmetrical.  So what's the outcome of this uneven body placed on a perfectly even machine?You guessed it; our hips don't sit evenly, and often don't move evenly on the saddle either.  The hips and pelvis are like a blow-off valve:  While we pedal our bike, we're not squirming our hands over the handlebars and our feet don't move much on the pedals other than the normal "float" motion that the pedals allow.  But the pelvis isn't "attached" to the seat in the way that our hands and feet are attached to their components.  So any imbalance through the body will translate up or down the chain to the pelvis.https://youtu.be/Y_niSoviUR0 For instance, let's take an easy example: Let's say you have a small rotation in your thoracic spine - a minor scoliosis - that rotates your upper torso preferentially to the right.  Your body is going to naturally counter-rotate to keep your head and neck facing forward (many people have scoliotic curves of varying degrees and you rarely see them walking down the street facing to one side, right?).  And on the bike we have a special set of biomechanical circumstances because the hands are resting on the hoods of the bar, so they're forced into an even upper body orientation, which magnifies the effect of our reflex to naturally counter-rotate.  So what happens?  This rotation has to go somewhere from the thoracic spine, and wile it might work its way up and settle into uneven posture between the shoulder blades, more often it goes down and usually forces the pelvis to twist to the left on the seat.Now this is just one very simple example and it almost never works out this simply.  There are usually other compensations that have taken place because these imbalances don't happen in a vacuum -- they're happening in the human body, which is a very complex and carefully balanced (or imbalanced as the case may be) structure -- this one thoracic rotation over time has developed muscular and other soft tissue compensations (some muscles in the spine will become tighter or weaker than others) and there will also be neurological changes as well since these limitations cause the body to use muscles unequally which will change the ability of the nervous system to activate them.This is why bike fitting is really such a complex task: regional interdependence, which is a fancy way of saying that changes in the system of the body in one location can have effects on other very distant segments -- because these effects are magnified by the rider being attached, to varying degrees, to the bike in five different locations.  Two hands, two feet, and your seat.  (I would make a case that it's actually six locations since we can count each side of the pelvis individually.)So, again, the saddle becomes the proverbial blow-off valve for the cyclist, and all this stems from the imbalances that exist throughout the body.Even some of the best  and fittest athletes in the world have these asymmetries.  I've tested thousands of athletes over the years from the world-class and professional level on down and I have always been able to find movement foibles big and small in all of them.So pretty much all of us sit skewed on the saddle, but what do I actually mean by this?  I mean that we sit off to one side of the saddle more, literally with one hip shifted towards the right or left side, and with our pelvis twisted -- one hip sitting further forward on the saddle.

How do we get these bike fit imbalances?

This lack of bike fit symmetry can come from a lot of different drivers.  Some people are born with structural imbalances or they develop them during their growth spurt at puberty.  People are most familiar with the leg length discrepancy -- when one leg is longer than another.  But our body is very good at absorbing these differences (especially since most people have differences that amount to a few millimeters).  On the bike, an actual leg length difference of 8 millimeters can be easily absorbed by the hip, knee, ankle, and mid-foot adapting their mechanics by a fraction of a degree each so that the shorter leg reaches the pedal.  But remember these differences don't occur in a vacuum; there will be muscle and fascial adaptations as a result of this leg length difference which will come into play, not to mention the neurological causes.Soft tissue differences -- those in the muscles, fascia, ligaments, tendons, etc -- can come from our structural abnormalities, as mentioned above, but also our habits and proclivities.  How we learn to do certain things is one such cause.  Ever notice that often kids run in a very similar pattern to their parents?  Or throw a baseball?  Or shoot a basketball?  We learn some of these movements and not all of them are beneficial or equal.  This can translate down into postural habits as well -- how we stand, shift our weight, or walk.  All of these habits will affect our symmetry.  I haven't even gotten to our handedness yet.But our structural issues, habits, and whether we're right or left handed doesn't account for the patterns that we see during bike fittings.  This is because most people, likely upwards of 70% or more, sit to one side of the bike -- the right.  Why would so many people be biased towards this side?  Remember, this happens independent of whether they're right/left handed or footed.It is because of an idea called lateralization of the body.  That we are wired towards one side.  There are many theories about why this occurs, but on I like quite a bit has to do with the ultimate core muscle:(Keep in mind that this is a known theory, not invented by me.  And as a theory it can't be ultimately proven, but I think it makes a lot of sense.  Also, this is going to be a very simple run through of this theory -- a whole book could be spent on just this topic)So the structure I'm referring to is our diaphragm.  For those that don't know, our diaphragm is a dome shaped muscle that lives under our rib cage that helps with breathing.  As the diaphragm contracts it pulls down into our abdominal organs which creates space above it for the lungs to expand.  Where the imbalance comes from is that the right side of the diaphragm is thicker and stronger than the left because the right side lives above the liver, which is a big dense organ.  Underneath the left side, we just have the stomach which provides a lot less resistance to the contraction and descent of the muscle.  Because the right side is thicker and stronger, and it attaches to the spine from T8-L3 (from the 8th thoracic vertebra to the third lumbar) it can exert a right rotation on the spine.And, BANG!  So begins the imbalances.  Or at least that's what the theory supposes.But not everyone sits this way on the bike -- I said only 80-90% did at the beginning.  What's going on with the other 10-20%?  And of the original 80-90% some of them sit to the left (some even sit square).  What gives with them?  Well, remember the two other ideas that are in play -- regional interdependence and that these imbalances don't happen in a vacuum.  So there will be other tissues at play that are pushing and pulling the body all over the bike and could countermand the root effect of the diaphragm.  (Also an individual could have what's called situs inversus, which is when the organs are flipped to the opposite side -- liver on the left and stomach on the right.  But this occurs in only about 1 out of every 10,000 people)

Bike Fit my Diaphragm?

If this unchangeable, anatomical structure's location could be causing your shift on the bike, it doesn't instill a lot of motivation to try to do anything about it.  But remember:We are not an experiment in a vacuum -- other tissues and structures are involved.We are best served by finding as many of those other prblems -- the weak lumbar region, the restricted rectus femoris muscle, the messed up functional movement patterns -- and work on them.  You may never be a perfectly equal, functional machine -- in fact the likelihood of this is pretty slim -- but the closer you are to even, the better you're going to fit your bike.