By Fred Matheny
There can be a conflict between results of lab studies versus real-world experience. Often, the researchers conclude one thing while clinicians and coaches find the opposite to be true. This conflict between scientific conclusions and a real cyclist’s performance on the road was clearly shown in a series of biomechanical studies undertaken by Maury Hull, Ph.D., from the Biomedical Engineering Department at the University of California at Davis.
Hull noted that 25% of all cycling injuries involve the knee. Patellofemoral pain (in front, under the kneecap) was the chief knee complaint. Hull hypothesized that tibial rotation during the pedal stroke might cause friction and pain under the patella.
He theorized that because pedals with float allow the foot to rotate laterally a few degrees before reaching the release point, this might make the tibia rotate during pedaling and cause the patella to ride to one side or the other of the femoral groove. That wouldn’t be a good thing.The patella needs to stay in its groove where cartilage can protect the bone surfaces. When the patella moves away from the proper track, either from muscle imbalances or other factors such as tibial rotation, the cartilage is threatened.
One problem: it’s difficult to measure directly the friction under a living person’s kneecap. So Hull devised a machine that could rotate the tibia of a cadaver knee while simultaneously pulling on various muscles and tendons to simulate the pedal stroke.
Because he was using a cadaver knee, Hull could peel back the skin around the patella. He inserted friction-sensitive film between the backside of the patella and the femoral groove. The film then recorded where the pressure was greatest.
Hull showed a slide of the apparatus with a cadaver knee in place, going through the motions. From this experiment, he concluded that tibial rotation can indeed cause unwanted friction to the back of the patella.
Hull’s recommendation then is that pedals should not allow any float.
Hull also was interested in whether wedging or shimming the cleat might exacerbate kneecap problems. Wedges are popular among bike fitters to solve alignment problems. When looked at from the front, the rider’s kneecap should be directly above the foot and in line with the hip joint throughout the pedal stroke.
If the foot collapses inward due to a weak arch or other problems, it can be shored up with judicious use of wedges commercially available (such as the one pictured) placed between the cleat and shoe sole. In almost all cases, the thick side of the wedge goes under the inside of the shoe toward the crankarm, thus tilting the foot slightly to the outside in a position known as varus.
However, Hull’s cadaver knee did better when the thick side of the wedge was placed on the outside of the shoe, thus everting the knee toward a knock-knee position.
This conclusion drew audible gasps from the audience composed of many professional bike fitters. It runs counter to general practice and counter to the observations of top clinicians. It was a clear case of a carefully designed study that concluded exactly the opposite of what years of practical and clinical experience had discovered.
Does this mean that Hull’s study was flawed? Does it imply that we can’t trust science? Or does it mean that common sense and experience have once more been trumped by inventive research? After all, common sense has been a notable casualty of science for hundreds of years. Common sense tells us that the earth is flat, that it is stationary while the sun moves around it and that light can’t behave like both a particle and a wave at the same time. But science has shown these commonsense ideas to be faulty. If that’s the case here, we should all purchase pedals that don’t float and shim our cleats so we ride knock kneed.
It’s important to note that Hull is no scientific lightweight. His research has spanned more than 30 years and is highly regarded in both the scientific and cycling communities. He’s a longtime cyclist himself. So there’s nothing inherently wrong with his studies or their methodology. However, they point out the gap that sometimes exists between a tightly controlled study and the varying conditions we experience on the open road.
Why should we view Hull’s conclusions with care? Here are 4 caveats expressed about the study:
- A cadaver knee isn’t a living knee.
- A pedal stroke simulated by a machine isn’t the same as an actual pedal stroke.
- The impact of pressure under the kneecap is hard to measure. Arthroscopic examinations show us that some riders whose patellas are pitted and worn on the back side experience no pain. Others, with less visible damage, can’t ride at all. The absence or presence of pressure may not mean much.
- A small minority of riders do fine with no float and an everted foot. Maybe the cadaver was one of them. As Hull himself notes, the anatomy of different riders can vary significantly.
So what’s the bottom line? Take any study with caution. Hull’s findings may apply directly to you — but it’s more likely they don’t. Until a study’s conclusions have been replicated, preferably many times, be wary.
And if the study suggests you make changes in your riding style or position when you’re already injury-free, you’re better off ignoring the temptation. Stick with what works for you.