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Tech Report - Challenging assumptions
By Lennard Zinn
VeloNews technical writer
Filed: January 29, 2008
The first day of the second annual Serotta Science of Cycling Symposium offered participants some welcome opportunities to take on a few sacred cows of the sport.
Among those taking jabs were gored by professors Maury Hull, Ph.D. of UC Davis and Jim Martin, Ph.D. of the University of Utah. The gored cows were partially resurrected by Andy Pruitt, Ed.D. of the Boulder Center for Sports Medicine, and Katrina Vogel, MS, DPT, a Seattle physical therapist, and perhaps by Jeff Broker, Ph.D. of the University of Colorado/Colorado Springs. Conrad Earnest, Ph.D., the director of the Exercise Testing Core at the Pennington Biomedical Research Center in Baton Rouge, Louisiana, gave a compelling synopsis of both the history of testing of Tour de France cyclists and the history of the Tour itself.
It was a high-powered panel in Boulder
Hull led off with a discussion of his Shimano-funded research into foot position pedaling mechanics. He studied twisting moments and bending moments about the knee during pedaling. Using sophisticated setups in the Biomechanical Engineering in Sports Laboratory and the Orthopedics Biomechanics Laboratory at UC Davis, Hull studied the effects of floating pedals and canting of the foot on the rotational and lateral moments of the knee and demonstrated that minimizing those moments is desirable for pedaling efficiency and for injury prevention.
Using the knee of a cadaver hooked up to tension devices to pull on muscles and tendons while the fixture applies internal rotational and varus (i.e., outward, or bowlegged) bending torques on the tibia, he measured pressure under the kneecap. He showed that together, internal rotational and varus bending torques on the tibia greatly increase the pressure under the kneecap and hence increase the likelihood of Patello Femoral Pain Syndrome, a common cycling knee injury.
He also measured cyclists pedaling on an ergometer with EMG electodes hooked up to show activity of the vastus medialis oblique (VMO), vastus lateralis (VL), and tensor fascialatis (TFL) muscles. These three muscles apply tension on the iliotibial band, inflammation of which is another common cycling knee injury.
The upshot of his research skewered two rather sacred beliefs of cycling fitters. One of his conclusions is that floating pedals do not reduce the rotational and lateral moments about the knee and are hence of no use in preventing knee injuries. The other conclusion is that 10 degrees of valgus canting (i.e., tipping the foot inward, or knock-kneed), reduced rotational and lateral moments about the knee and are therefore beneficial in preventing knee injuries.
Pruitt, director of the Boulder Center for Sports Medicine spoke from a clinical perspective about cycling knee injuries and what he has learned in a quarter of a century of treating them. Interestingly, his clinical findings were almost diametrically opposed to the lab conclusions of Hull.
Pruitt works as an exclusive design consultant to Specialized Bicycles on its Body Geometry products, and he notes that while the knee is the No.1 injury problem in cycling, cycling is the No.1 recommended therapy for knee injuries. To him, the knee is the victim, and the hip and ankle are the culprits.
He has found that floating pedals, both in rotational and translational freedom, have greatly reduced the incidence of ilio-tibial-band knee injuries, which became "epidemic" in the early 1980s with the introduction of clipless pedals without float. He showed gruesome photos of the surgery he helped pioneer at that time of cutting an oval hole in the IT band to reduce its tension and hence its irritation when rubbing along the side of the knee during pedaling.
Pruitt also reported a reduction in a variety of knee injuries as well as an increase in cycling efficiency by canting feet outward (varus canting); that's also the opposite of Hull's research findings. The Specialized Body Geometry shoes that are his brainchild have this feature built into the sole. They also have insoles with medial (i.e., longitudinal) arch support as well as metatarsal arch support. While he did not address the latter in his talk, he did discuss how the collapsing of the medial arch, while it serves a purpose in walking by storing energy to be given back when springing off of the foot, has no use in the cycling downstroke. "You don't want to store energy during the downstroke," he said, "you want to deliver it."
Martin skewered sacred cows about crank length, pedaling technique and rider positioning. We were forewarned, though, as he said at the outset that many of us would find his conclusions "irritating."
His studies of 16 bike racers of various heights doing maximal sprint power tests of under four seconds duration on cranks of 120, 145, 170, 195, and 220mm showed no statistical difference between crank lengths. Seat height to the pedal was maintained throughout, but fore-aft saddle position and handlebar height were not readjusted with crank length changes, despite variations with crank length of pedal-to-knee relationship and saddle-to-bar drop. This also led to Martin's assertion that he could see no point to positioning the knee over the pedal spindle.
Further Martin tests showed no statistical relationship between metabolic cost and either pedaling rate (RPM) or crank length, using nine trained cyclists riding 145, 170 and 195mm cranks who pedaled at 30-, 60-, and 90 percent of their lactate threshold at 40, 60, 80 and 100 RPM. On the contrary, power output and pedal speed (pedaling rate times crank length), accounted for over 98 percent of the variation in metabolic cost.
In another test, Martin had 10 racers perform a 30-second maximal sprint on 120mm and 220mm cranks at 135RPM for the 120mm and 109RPM for the 220mm. he found that, while the rate of fatigue was less for longer cranks, the fatigue per revolution was identical. This led him to suggest that track sprinters, rather than spinning at high RPM, should select the gear at or just below the one at which they produce maximum power output. The higher gear, as fatigue per revolution would be constant, would get the rider to the finish sooner, as fatigue would take more time to set in.
Finally, Martin's studies of pedaling technique indicated that regional cyclists had "better" pedaling mechanics than elite cyclists. It indicated that elite riders pull up less on the pedals on the backstroke and push down harder on the downstroke.
By studying 13 trained cyclists and 35 fit athletes who did not own bicycles, he also showed that non-cyclists, who started out lower on the first day, produced higher power outputs by the 4th day than trained cyclists. They also hit their maximum power at a higher RPM than the cyclists. The total time to learn to produce more power by the non-cyclists was three days and a total of 36 seconds of hard pedaling! This seemed to dispel the ideas that cycling adaptation takes time, that pedaling technique refined over time is important, particularly to learn to pedal efficiently at high RPM, and that avoiding "working against yourself" on the backstroke (revealed in graphs showing a net negative torque past bottom dead center) is useful.
Martin says that you are then left with two things to go faster. Hard training and good nutrition, hydration and recovery are the keys to maximizing the power you can produce. And reducing aero drag and reducing braking are some ways you can minimize the power you must produce. That's it. Simple.
Earnest, in his "105 Years of Cycling, Science and Legend - Lessons from the Tour de France" talk, gave audiences glimpses into the history of sports science as well as into the history of the Tour itself. He related study after study over a century from which we have gleaned much of what we know about cycling and training for it. He drew gasps, for instance, with his photos of a cyclist riding with the first "portable" heart rate monitor. The thing was strapped to his back, weighed 75 pounds, and was the size of a large backpack!
The Pennington Biomedical Research Center focuses on studying diabetes and other overweight-related diseases and syndromes. Noting that, "there is no nice thing about cycling in Baton Rouge," after originally starting his sentence with, the "nice thing about cycling in Baton Rouge," Earnest pointed out that there is only one safe road to ride on, and it is flat. This has led to a proliferation of cyclists who focus on time trialing. He also pointed out that Louisiana consistently comes in second to only Mississippi for having the most obese population in the USA. These two characteristic populations has made it an ideal place to stuffy obesity vs. time trial performance. The resulting study showed that, in a flat time trial, taking 3kg of mass off of the body results in almost twice as much time reduction as removing 3kg from the bike. As the Tour's pivotal stages are generally either time trials or mountain stages, this is an important finding.
And looking at mountain stages, another interesting study was the climb of René Pottier in 1905 up the Grand Ballon d'Alsace. On a single-speed fixed-gear bike, he was the first to reach the top of a mountain in the Tour by not only being the only one to make it up without dismounting, but also by pedaling up it at an astounding 20kph. Earnest's research shows that ride to be an amazing accomplishment even by today's standards, despite the fact that he punctured on the way down, thus losing the stage, and that he withdrew the following day due to tendonitis. Pottier apparently put out an average of 370-390 watts up that entire climb. No wonder he came back to dominate the next year's Tour, winning five stages. Sadly, he committed suicide in 1907, hanging himself from a bikehook.
Other studies focused on the Banesto team in the Vuelta and the Tour, thanks to Earnest's close collaboration with the lead researcher in those studies. One interesting one showed that, over the three weeks of the Tour or the Vuelta, a rider's maximum achievable heart rate drops. Another showed that a wide range of cadences can work for a rider. It demonstrated no difference between 80 and 100RPM in oxygen uptake at a certain power output and a small dropoff at 60RPM, but that adaptation takes time is required for maximum efficiency, and could probably erase this difference as well. A nutrition study indicated that performance is improved by taking in fructose and other high-molecular-weight sugars, rather than simple (low-molecular-weight) sugars.
Vogel, like Pruitt, discussed the value to the majority of cyclists of varus foot canting on the pedals and pointed out a number of clinical cases. She discussed the rarity of valgus canting as an indicated therapy and the possible, albeit dangerous due to likelihood of low-back injury, of "spring loading" the tendons and ligaments of the hip through valgus canting. She noted the theoretical opportunity to slingshot energy from the one side of the hip to the other this way.
Broker spoke at the same time about cycling biomechanics, and as pedaling mechanics was the focus of much of his work while working for the U.S. Olympic Committee, it would have been interesting to see how it squared with Martin's surprising revelations. But alas, I could only be in one place at a time.
The symposium continues tomorrow and Wednesday. Tomorrow I will also meet with Active-Spoke, a company whose product is a little weight with a spring attached to it. The weight goes on a spoke and moves more rotating mass out to the edge of the wheel when it is spinning fast. When the wheel is spinning slowly, the springs bring the weights back to the center of the hub.
