Considerations When Fitting a Symmetric Machine to Our Asymmetric Bodies
During fittings, I regularly see significant problems that cause cyclist’s pain and discomfort during and after riding. Though there are several common problems, I’m going to highlight the top 4 and give you some insight on how to avoid them. Before I get into the specific problems, it helps to understand the underlying issues of fitting a bike to a rider.
The Core Issue
The inherent problem in riding a bicycle is the fact that you are coupling an asymmetric machine (human body) to a symmetric machine (bicycle). Our body gives us precise feedback and clues as to how it is adapting to the bicycle. There are 9 touch-points between the body and the bicycle; 2 for the feet, 2 for the hands, 2 for the sit bones, 2 for the pubic rami and 1 for the soft tissue. They all work together to support the body. Correct alignment is absolutely critical to maximize power and minimize injury.
If this interface is out of alignment, then the rest of the body will compensate for this misalignment by heels moving side to side, knees diving in and out, hips and buttocks twisting in the saddle. And that’s just one pedal stroke. Multiply that by 10,800 pedal strokes during a 2-hour ride and you quickly have the makings for a repetitive injury.
Other asymmetrical properties to consider are leg-length discrepancy (structural, functional, legs of different length, which is not uncommon), scoliosis (spine curvature, also not uncommon), one side of the body stronger than the other, etc. Any misalignment can manifest itself in discomfort, pain and/or injury. There are even more things that can compound the problem of an uncomfortable fit such as, incorrect saddle width, seat too low/high, stem too short/long, and crank arms that are too long.
Top 4 Common Fit Issues
1. Crank arms that are too long.
Pouring over thousands of my clients fit data, I started seeing a pattern of exactly where they said they experienced pain. Most cyclists listed “knee pain” as their number 1 issue. As a fitter, I can and have to fit the leg that is at 6 o’clock, but it’s the leg that is at 12 o’clock that is causing their knee pain. When a crank arm is too long, this knee is hyperflexed causing excessive sheer forces to the articular cartilage which, in turn causes damage to this cartilage. My daughter (Doctor Physical Therapy) and I wrote a paper for the medical journal, Lower Extremity Review, that discusses this problem and recommended solution in detail.
2. Bad cleat alignment.
When a cyclist pedals and his/her knees splay out to the side at the top of the pedal stroke this is indicative of bad cleat alignment. Not only is this inefficient, but it’s also potentially damaging to the knees. When the knees go out to the sides in this way, you are not only over-stretching the lateral collateral ligament, but also putting extra pressure on the lateral condyle and lateral meniscus. This is usually experienced by cyclists with wider hips who have their cleats positioned too far to the outside (i.e., shoes positioned too close to the crank arms). In more extreme cases, it is advantageous to add width to the cyclist’s stance by moving the entire pedal farther out. This can be done using 1-2 pedal washers or even using pedal axle extenders. Another problem with cleats is that the toe-in/toe-out is wrong, which causes additional stresses to the knees if this is not set up correctly.
When your cleats (and quite possibly pedals) are adjusted correctly, your knees will be tracking straight up and down. Good cleat placement also places the metatarsals directly over the pedal spindle so that when you are in your power stroke, your feet are positioned and knees aligned to be able to help provide the maximum force to the pedals – with no undue stress on your knees. A good bike fitter can have your knees going straight up and down during the first visit.
3. Combined problem of saddle height and saddle fore-aft positioning.
Many cyclists are either too high or too low in the saddle, as well as either too far back or too far forward. Being too high can cause the knee to be hyperextended, which can cause knee pain at the rear of the knee. Being too low in the saddle can cause the knee to be hyper-flexed, which can overstretch the cruciate ligaments, causing pain in the front of the knee. The cruciate ligaments are the major stabilizing ligaments in the knee and can be more easily damaged in those cyclists who produce more power. The correct saddle height allows the cyclist to pedal with force midway between these two endpoints, which allows the cyclist to generate the most power without damaging the knees.
The other saddle issue I often see is bad fore-aft positioning. Many bike shop employees and even some bike fitters will use the saddle fore-aft to adjust the rider’s reach and comfort to the bars. But that’s wrong. Saddle fore/aft positioning is actually for placing the knees over the pedal spindles and should not be used to adjust the reach to the bars. Use a different length stem for adjusting reach to the bars.
The real reason this positioning is critical is that when done correctly, the knees are placed directly over the pedal spindles so that when the cyclist is generating their highest power and pushing the hardest on the pedals, their knees are pushing straight down and not forward or backward. While there is some leeway in this adjustment, the closer the cyclist is to the correct measurement, the less stress there is on the knees.
4. Handlebars that are too low and too far away from the rider.
Many cyclists like that “pro-racer” look but don’t have the pro racer body to pull it off. Most cyclists lack the flexibility and core strength to support this aggressive position. This “too-low & too far” position causes over-stretching of the hamstrings, which not only robs a lot of power but also causes a sore lower back.
Correct bar height (via correct stem rise, length and number of spacers) will help you achieve a flat back which, coupled with rotating your pelvis forward will allow you to provide maximum power to the pedals while minimizing any lower back pain.
How Can You Avoid These Problems?
If you’re buying a new bike, start off with a quality bike sizing before you purchase your new bicycle. Make sure to deal directly with a bike fitter or a shop fitter that is trained and certified in bike sizing. This is the most important step in the process. With a frame that doesn’t fit you, a bike fitter can only do so much to accommodate your body to the machine. For your preferred frame, a qualified bike sizer will be able to tell you your exact frame size, crank length, best pedal options, stem length, best saddle(s), best handlebar width and even the number of spacers that will ultimately be placed between the stem and headset.
Once you get your new bike, go directly to the fitter to get a thorough bike fit where these items (and more) will be fine-tuned to fit you perfectly. Make sure they measure both Max Extension and Max Flexion angles of the knees.
On your existing bike, if you think you may be suffering from any of the problems discussed here, you can take the steps noted to improve the fit for that particular issue. However, there may be more underlying issues, and I would be remiss if I did not recommend a professional bike fit by a qualified fitter. (Note: our bodies change over time, too. A fit you had done as recently as five years ago may well not be the best fit for you today.)
In summary, most, if not all of these injury-causing misalignments can be fixed by a fitter who works closely with a physical therapist. Depending on the ailment, the bike fitter might only be able to go so far in the initial fit. A good bike fitter will discuss with you the need for a physical therapist to look at and possibly treat a given issue. After treatment, the bike fit can be continued to a successful and injury-free conclusion. If in doubt, write or call me for some help.
You can find out more about Rick Schultz’s coaching and fitting at Bike Fitness Coaching.