I saw a consultant orthapaedic surgeon a few days ago, after a fourteen week wait.
In a nutshell, the result is; the pelvic tilt is due to the residual post-operation scoliosis and is
uncorrectable. (I have a 14 degree primary curve in the upper spine, which leads to a sympathetic
curve in the lumber region, which leads to the pelvic tilt.)
However, the discussion we had has given me a new idea or two.
First, I experimented to see if I could properly detect the difference in effective leg length while
seated on my bike. I sat as I would normally, except without shoes and with the pedals out of the
way. The bike is resting on a trainer, so there are a pair of parallel plastic bars under the bike,
one each side, which I can easily rest my feet against, when I stretch my legs and feet down to
reach the ground.
I then slowly slid my feet backwards, keeping them level, until the big toe was just reaching the
ground. I found that when my left big toe was just reaching the ground, my right big toe was
distinctly off the ground.
So, I had positively found a real difference in effective leg length through a simple experiment.
Had a friend been with me, it would have been easy to measure the difference in length.
Next, I experimented with deliberately tilting my pelvis to compensate.
This required me to use my muscles to lift the left side until my feet reached the ground equally.
This takes a moderate constant effort.
The problems here are that it requires this specific effort (which presumably would become easier
with time, from practise), that it seems to inhibit breathing somewhat (or perhaps enhances it, and
the feeling is unfamilar?) and finally, that it moves my torso off of the center line of the bike,
over to the right.
The advantage (the blessed advantage!) is that both legs are now *right*. Halleluah!
In fact, having done this experiment, a vital fact of the utmost importance has become clear to me.
I have realised that if I permit my pelvis to sit as it naturally wishes on the saddle, not only is
there a leg length difference, but that the legs are *no longer centered over the pedals*. Normally,
riders push directly downwards. In my case, both legs are centered to the left of their pedals,
since my pelvis tilts down towards the left. Accordingly, on the downstroke, my left leg is pushing
in towards the bike and my right leg is pushing outwards, away from the bike.
This non-vertical angle is a huge problem when it comes to obtaining riding efficiency and comfort.
Legs are designed to push *down*, not down *and sideways*. The pattern of muscle use changes and
indeed is different for each leg, since one leg is pushing in, the other out.
What's more, this is the explanation for the different muscle activation and use patterns in each
leg; left leg pushing in (outer, left side, muscles working) right leg pushing out (inner, left side
again, but of course the *inside* muscles now since this is the *right* leg, muscles working).
This difference in muscle activation and use has puzzled me for long, long time!
So; I can deliberately tilt my pelvis, adjusting myself to the bike, or I can try to adjust the bike
to compensate for *me*.
I think, in theory, if I sit naturally on the bike, I can adjust for the pelvis tilt by adding leg
length adjusters to the shorter leg and moving both cleats over to the left.
A problem here is that the crank arms limit the amount of leftwards movement possible in the
right shoe.
Alternatively, the saddle itself could be tilted. This might perhaps not be too difficult - a custom
seatpost with a sideways angle or bend, or a custom saddle rail where one rail is higher than the
other. (The latter being preferable, I think).
...
I experimented today with adding length adjusters to the right cleat and moving both cleats
to the left.
The leftwards move did indeed alleviate the anomalous muscle use pattern in the right leg. (Legs
appear to be reasonably happy pushing down and inwards but now down and outwards, so the left leg
was never unhappy).
However, with the length adjusters in place, one problem remains, namely that the downward stroke of
the right leg is *still* not correct. The pivot point appears to be a few inches above the knee,
rather than at the knee, resulting in incorrect muscle use.
To experiment, I then removed all length adjusters, centered both cleats, and performed my normal
one hour high effort ride, while manually adjusting the tilt of my pelvis.
This worked well for my legs - and in particular, the knee pivot problem appeared to be resolved. I
noticed of course that the left leg was much more confident than the right leg, since the left leg
has performed in this position for a year now, whereas the right leg has not.
Manually adjusting pelvic tilt takes a certain effort, and remembering how much tilt you need to
apply is a bit awkward. I would imagine it becomes easier with practise. Breathing isn't
particularly affected, although it feels a bit different.
I'd prefer, I think, to sit naturally, since this requires no additional muscular effort or thought.
However, the paramount goal is optimal riding, and whichever solution turns out to be best for this
is the solution to use.
I suspect pelvic leveling is the right way to go, because a non-level pelvis introduces a world of
adjustments - it's has a very complicated set of effects on position. Being symmetric just makes
life SO much easier.
--
Callas