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Editor’s note: Last month Kit Vogel wrote about asymmetry in cyclists’ bodies (more accurately, among most humans’ bodies). The column produced a lot of comments and questions, so Kit checked with some experts and reviewed the literature and has more to say on the subject today.
Well, it looks like this topic hit a nerve and got people talking. Responses have come from all over the world and from several different clinicians and bike fitters. Clearly, the various responses have been fairly polarized and created a fantastic debate.
I took the advice of one of the more “prolific” responders and talked openly with several different types of medical clinicians in response to the idea of the presence of asymmetry within the pelvic region. The list included chiropractors, physical therapists and MDs. (Yes, we even discussed Gonstead methodology.) Almost everyone agreed that asymmetry within the pelvis is both “common” and “normal” within the human species. The question is, when does it become a problem? Some medical clinicians were in agreement of the natural bias to the anterior right/posterior left; there was also some strong statements that, “no such pattern exists.”
Keep in mind that most of these conversations were in relation to standing, walking and all other activities of the vertical nature. Very few medical clinicians were also professional bike fitters and most did not actually know how the mechanics of the pelvis changed once the pelvis was closed chain on a bike seat … because the mechanics do change. The end result of these conversations revealed that there is a difference of opinion between the different medical professions as well as medical professionals within those professions, depending upon their training. For this particular topic, we will focus on the pelvic mechanics that occur on the bike because this is, indeed, a bike fitting forum.
Norkin & Levangie (1992) was mentioned several times within the thread and is a great text and reference. On page 317 (Table 10-1), the text states that an anterior rotation of the innominate is accompanied with an internal of the hip joint/femur. A posterior rotation of the innominate is accompanied with an external rotation of the hip joint/femur. This is also stated on page 17 of Gonstead Chiropractic Science & Art (1980). This is the exact mechanic that is seen on the bike in relation to the position in which cyclists most commonly sit on the bike saddle: rotated posterior on the left and relatively anterior on the right, therefore creating a tendency to have a lateral tracking left knee and medial tracking right knee as driven from the pelvis that is fixed upon a symmetrical saddle. (Feet will be discussed at a later date.)
How can this be? Frankly speaking, this pelvic asymmetric position is an observation that has been made by clinicians/bike fitters for several years. This doesn’t come from an ivory tower. This information comes from working in the trenches of bike fitting for several years with greasy hands and bike tools strewn around. It comes from the application of clinical knowledge in relation to a sport that is stricken with overuse injuries from cyclists attempting to bend their bodies to the specs that were decided by bike and component manufactures in a factory. Our responsibility as bike fitters is to fit the bike to the cyclist and their individual biomechanical needs. It is wrong to make a cyclist adapt their asymmetrical body to a symmetrical bike.
Julian from Cyclefit wrote, “We can’t assume that the distance between the pedals on a bike is correct (who decided that anyway?) for everyone or that it should be the symmetrical.” Pedal spindle length (outer crank arm to center of pedal) in most brands traditionally is 53 mm. According to pedal manufacturers, this width was decided “several decades ago” as the width needed to fit a shoe upon a traditional flat pedal. Look at the people standing around you. Nobody has the same exact stance width. What would happen if we decided that everybody should walk and run with the same stance width? Frankly, there would be some major problems and (inevitably) injuries. Therefore, it better serves cyclists to adapt the stance width to their individual needs rather than lock them into a stance width that was decided by the width of a shoe several decades ago. More than likely, the stance width will be different for the right and left leg, with the left foot needing to be more lateral than the right to be underneath the knee. This is based upon basic biomechanics of keeping the foot underneath the knee.
Regarding the feet … Of course they play a significant part in asymmetry within the legs and this information can be clearly seen in any other written information we have ever posted from Bike Fit ©. However, the focus of this forum is pelvic mechanics and its effects upon the prevalence of left lateral knee tracking. We can cover foot/LE mechanics at a later date. (Just to wet some whistles … the tendency still appears to drive a left lateral knee. Curious?)
Asymmetry within species is the expected norm within evolutionary biology as a means of making locomotion more efficient (Shapiro et al, 2004). The human animal is no different and is certainly no exception to the rule. However, there is a lack of academic research in relation to pelvic mechanics and cycling. Sauer et al, 2007, has some interesting information but, as seems to be the pattern with pelvic research in regards to cycling, it references the pelvis as a whole unit and does not address the inherent asymmetries.
While cycling, the left SI tends to jam more than the right because of the forward flexion of the trunk, the inferior pressure of the saddle against the ischial tuberosities in addition to the posterior rotation of the left innominate. Is this true for everyone? No, but it tends to be an issue that is common within cycling. This can be addressed by tilting the nose of the saddle down (slightly at 2-4 degrees), which imparts a mild anterior rotation of the entire pelvis. Funny … it also allows the left SI joint to unlock and function more symmetrically to the right by creating an anterior moment for the pelvis. How could this happen if it wasn’t posteriorly rotated? The stem can also be made shorter and steeper. These changes tend to allow the left knee to move more medially, although it is unlikely to fully correct for the lateral placement of the left knee.
Clinicians that don’t do bike fits: Challenge yourselves to look at the pelvic pattern within your cyclists (WB & NWB). In fact, look at them on their bike and tell us what you see. Do a March test for SI joint motion assessment. Assess the motion of the sacrum, innominates and lumbar spine as they ride their bike. Track their knees with a laser and see what is going on from the top of the upstroke to the bottom of the down stroke. Tell us what you see.
Bike fitters and clinicians that fit bikes: Track the knees of your cyclists before any medial-lateral adjustment is made to their cleats. Use a laser and dots to accurately assess the motion of the right and left knee. Keep track of it and tell us what you see.
Joint adjustments, manual therapy and manipulations absolutely have their place in working with and treating cyclists. Neuromuscular re-education and a home exercise program are also an important aspects and treatments for cyclists. However, these treatments will be of little use if the cyclist is perpetually fighting the geometry and specs of a bike that does not fit their body.
Accurately fitting a bike to an asymmetrical body is not a compensation. A good bike fit alters the bike to fit the individual cyclist and their biomechanical needs instead of making the cyclist adapt their asymmetrical bodies to a symmetrical bike designed by designers/engineers in a factory.
— Katrina Z. Vogel, MS, DPT (“Kit”)
Katrina Z. “Kit” Vogel was described as one of the “rock stars of cycling science” in VeloNews in 2007. She earned her Doctorate in Physical Therapy at USC and MS in Biomechanics/Human Movement & Performance at WWU. She is the Director of Education for Bike Fit Systems, teaches clinically-based bike fitting classes and guest lectures in Biomechanics for the University of Wash PT Department. She is a Cat. 2 track cyclist.
Any information or advice offered by the members of the Coaches’ Panel should not in any way be viewed as personal medical advice. The recommendations made in this column are offered as general information for healthy, physically fit amateur and professional athletes. None of the information provided by members of the Coaches’ Panel should be viewed as a replacement for personalized, professional medical treatment or to replace the advice or services of your physician. While some members of the Coaches’ Panel are Licensed Medical Doctors, Licensed healthcare professionals, and certified coaches, their advice in no way establishes a doctor-patient relationship between the writer and readers of this column. If you are beginning or resuming a vigorous exercise program, it is important to visit your health care provider for a complete physical examination in order to identify and treat any potential risks you might face.