Bicycles are symmetric, carefully designed objects......sometimes as meticulously crafted as aerospace parts. It is this symmetry that ensures they handle well and are balanced. Most carbon bikes are made from moulds and so the integrity and alignment of the rear dropouts, the seat tube, and the head tube is maintained at all costs with these clamshell-like devices. Welded metal bikes are assembled on expensive jigs that ensure the same alignment. From there, fork steerer tubes, stems, and handlebars are equally symmetric.
All of this is done to make sure that a rider's weight is draped evenly over the bike. That way the left hand is the same distance from the frame as the right, as are the knees, hips, and shoulders.
Balanced body makes for a balanced rider. Makes sense, right? It stands to reason that your body is bisected by the bike itself. It sounds logical, but unfortunately, for the vast majority of us, it's not true.
The truth is that while our hands and feet are placed symmetrically on the bike (the right and left foot are situated on the pedals in nearly exactly the same spot on opposite sides of the center-line of the bike and same goes for the hands), roughly 75% of the population does not sit square on their saddle -- meaning we are shifted off to one side of the saddle, so effectively our hips, knees, and likely our shoulders are skewed to one side. On-the-bike infrared measurements (Retul) make discovering this fairly easy as long as you know what you're looking at.
To further complicate the matter, a large portion of riders sit with one hip further forward, but that's another article for another time.
[I know there are some of you out there asking "a leg length discrepancy can cause that, right?...can't that be the culprit of this skewed sitting posture?" Sometimes, but not as often as you'd think. You see often (I don't have firm numbers on this one, but in my experience about 50% of the time) a rider's leg length discrepancy doesn't come through on the bike as you'd expect it to -- i.e. a longer right leg should "push" the rider to the left so that the shorter left leg can more easily reach the pedals. Chalk this up to not being able to rely on simple mechanics when you're talking about pedaling a bike since no other task involves being attached to a machine in five spots as well as the more complicated neurological process mentioned below.]
How to remedy the derriere shift?
Since the bike won't accommodate us by having the saddle placed off to the side (moving the seat off-center so that it's under the skewed hips) we have to find a way to bring the rider back closer to being aligned with the bike.
In order to come up with a proper fix, we need to know why most of us can't keep our butt on the saddle squarely. The answer lies deep within our brain, where our most basic motor impulses come from. You see most of us, despite whether we're right or left handed are "wired" to favor our right side. So most (in the ballpark of 60%-70%) of those riders shifted off to one side of their saddle are shifted to the right.
First inclination would be to just force yourself to sit towards the center -- if the infrared shows you're in fact sitting to the right then you could just consciously sit further to the left. And off you go, right? Well, no. Problem is that conscious corrections really don't get you very far because you can't "attend" to this left-sitting posture for an entire ride and you'll end up gravitating back to the right especially as you work harder on challenging terrain. You've done very little to change the motor plan and so the problem will persist.
No, the best and lasting way to fix this is to get the weak side engaged more. Again, more of us are wired right-dominant and we're likely to never fully change this but if we can make a small improvement in the weak side's proprioception, strength, and/or coordination we'll make a dent in the problem.
Most of my client's leave their bike fit appointment with a combination of fixes to work on the problem. Often these include some drills (on and off the bike) to improve the weak side's coordination -- even some dry land balance exercises can occasionally make an impact. Flexibility work may help improve the ease of the pedal stroke and make a small impact. Most often, and in my experience most effective, are cleat position changes to improve the weak side's proprioception --
literally how that side senses and feels the pedal and pedal-stroke.
In all these ways we can engage that weak side and the result is then the rider begins to gravitate more toward the center of the bike. The rider won't just pop right back to dead center on that first bike fit, nor should we shoot for that. I usually shoot for a 30%-40% shift back toward center that first day -- getting more than that increases the chances of us over-correcting and creating a problem elsewhere.
A recent bike fit showed that the client was shifted to the right so their overall deviation from the center was in the 72-74 mm range (meaning that their right side was measured roughly 36 mm further from their centerline and the left side was around 36 mm towards their centerline. After a few changes on the bike, including some cleat changes that 72-74 mm deviation was down to 47-49 mm. Not perfect but better. From there I can instruct the rider on exercises that are tailored to their particular deficits in order to keep the rider working on their imbalances.
Once the client leaves and does their first 10-12 rides in this position their affected soft tissues (muscles, tendons, fascia, etc.) will have an easier time progressively adjusting to this new posture because we didn't try to over-correct them the first time.
When client's follow up after about a dozen rides it's most common to see that they are now about 70% improved in their alignment. Usually if they didn't make any progress from here they would still be in good shape....it's unlikely we'd make someone 100% symmetric on the bike anyway but negative stresses on the body are limited long before the 70% threshold.
If you have aches and pains on the bike and you're not sure where they come from or if you just want to make sure you're not losing any efficiency being off kilter, then come in to get checked out.
Sometimes you can see some of this shift just from looking at a rider's hips from behind. Have any pictures that show you or a riding buddy sitting off-center? Send them in
here.
