Case Study - Pelvis Stability
Pelvic Stability
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Let’s discuss the importance of pelvic stability and some of the ways I have achieved this with my clients.
It is important to note that all voluntary movement begins with the brain, more importantly, the Central Nervous System (CNS) which takes information supplied by the eyes, ears, and other sense organs and receptors of the body. These receptors include the force feedback from your feet. More on that in another case study.
Once the CNS has its information, it selects the correct response, plans, and then sends nerve impulses to the motor branch of the peripheral nervous system. In other words, it dispatches messages to your legs to pedal the bike and balance itself.
So here’s the key of this whole case study. Master Bike Position Specialist, Steve Hogg, noted that the CNS prioritizes things in this order:
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Breathing
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Postural Stability
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Movement Control
There are several muscles responsible for stability and breathing when riding a bike. Therefore it is important that as your bike fitter, I reduce excessive pelvic rock and rotation. These are movements that exist for a few reasons, but all stem from the body protecting an important survival muscle group, the Hamstrings.
Pedaling a bike is a series of repeated hip extensions. A muscle firing pattern, often done incorrectly, on the less-dominant side of the body. I like to begin by addressing structural or functional asymmetries, observed from the posterior view, such as the examples below.
Here I corrected pelvic rock and rotation four different ways based on assessments both on and off the bike.
These four ways included:
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Using a 6mm shim to accommodate a perceived leg length.
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Rider biomechanical queuing following, saddle height, fore/aft, and tilt adjustments.
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Auditioning a wide range of saddles.
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Saddle height adjustment and rider queing.
SHIMS - (Before on left, corrected on right)
BIOMECHANICAL TUNING - (Before on left, corrected on right)
SADDLE SELECTION - (Before on left, revised on right)
SADDLE HEIGHT - (Before on left, revised on right)
PROPRIOCEPTIVE AWARENESS - (Before on left, revised on right)
When a rider presents a pelvic motion of a significant rock and rotation due to an excessive saddle height, it also shows up with significant plantar flexion at the bottom of the pedal stroke (toe pointing). It's always a clear-cut case as the worse of two evils, is a saddle too high.
In this case, we had a rider seeking a very aggressive position which he had the flexibility to hold. We needed to stabilize the pelvis to ensure he could hold the increased saddle to bar drop and produce maximum power.
HOWEVER - Please note that once a saddle has been selected and a fit is complete, the rider is responsible for holding a steady upper body, when riding in zone 2. The act of pedaling a bike is quite simple compared to downhill skiing. Some postural control is required.