Tech Report, with Lennard Zinn: The science behind the sport – Part II

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By Lennard Zinn

Lastweek I reported on the first day of the CyclingScience Symposium and Expo at the Hotel Boulderado in Boulder, Colorado.

The conference featured a second day of lectures, followed by a third expo day at which purveyors of equipment and services for improving cycling performance offered their products for public view. Tied up by other commitments, I was unable to attend the expo, but I did find the second lecture day to be fascinating.

Computer-modeling your muscles
Dan Heil, Ph.D., FACSM, an associate professor of exercise physiology at Montana State University in Bozeman gave a very interesting talk about using computer modeling the determine optimal cycling position. Starting at the level of the sarcomere, building up to the myofibril to the muscle fiber and finally to a complete skeletal muscle, and looking at the force versus length curve for each of these sub-units, Heil explained how torque on a joint applied by a skeletal muscle could be predicted and modeled.

By understanding these relationships at their most rudimentary levels, he described how training at different joint angles (i.e., changing to a new position on the bike) could change the number of sarcomeres, which could change the muscle force vs. length curve and hence the muscle torque vs. joint angle, ultimately changing the ability to generate power.

Heil described a considerable volume of research focused on the subject of body position on the bike and efficiency. In his own work, for example, Heil studied the relationship between hip angle and oxygen uptake for a rider on a bike.

Heil created computer models of rider hip angle vs. seat-tube angle and how the optimal position in terms of seat angle, for instance, could be predicted from research into rider oxygen uptake at various hip angles. The model can further predict how much the rider’s wind drag varies with seat angle and combine the two to optimize the chosen saddle position.

The importance of fit
As I said last week, this was a collection of the superstars of cycling science, and one of the biggest of those is Andrew Pruitt, Ed.D., the founder and president of the Boulder Center for Sports Medicine. Working to compress years of data into the time allocated at a seminar, Pruitt went through the medical aspects of bicycle positioning. Specifically, he dealt with the myriad ways that cyclists can injure themselves with poor position or body mechanics and how such injuries can be subsequently treated.

“The two things that increased the medical aspects of bike fit more than anything else were clipless pedals and aero’ bars,” said Pruitt, because they both tended to lock the rider into a certain position, and, if not perfect, could cause injury through repetitive motion in that improper position.

“The black (fixed-position) Look cleat was great for business,” he added.

Pruitt also described how Greg LeMond’s publication of his ideas on rider positioning created significant back pain among many devotees, simply because the three-time Tour winner had a physique – with extremely long thighs and short lower legs – that allowed him to ride comfortably in positions that few others could.

“Greg wanted everybody to look like him, and that, too, was great for business,” quipped Pruitt.

Pruitt noted that many of the maxims of bike fit – for example, the old Knee Over Pedal Spindle (KOPS) system so popular with bike fitters – are oversimplifications that can lead to host of their own problems.

KOPS, noted Pruitt, assumes that the center of rotation of the knee is in a clear location.

“We (bike fitters) talk about the ‘center of rotation of the knee’ as though there is bolt going through the knee,” said Pruitt. “Nothing could be further from the truth. The end of the femur is elliptical, not round, and in fact the end of each condyle on the end of the femur has a different elliptical shape. We’re just guessing, guys!”

Pruitt described studies of overuse injuries of the knee with hundreds of cyclists and how those problems originally developed. He showed slides of corrections to cleat and saddle positions to treat these conditions, as well various methods of diagnosis and therapy, including steroid injection therapy and over-the-counter anti-inflammatory therapy. Pruitt even showed graphic photos of “percutaneous release” performed in an office. In other words, he showed how an oval chunk could be cut out of the ilio-tibial band to treat IT band pain syndrome.

Getting aero

While a lot of roadies might poo-poo triathletes’ strange forward position, Kautz clearly demonstrated how it had evolved as means of limiting stress on hamstrings. The position puts less stress on the hamstrings, but also has to accommodate a hip angle that’s still tight enough for the gluteus muscles to fire. A basketball player, for example, has to compress his hip angle in order to explode up from the ground when jumping to dunk the ball.

Kautz, however, showed that rather than continually moving a triathlete up and forward to remove stress from tight hamstrings, the rider could be better off – and faster – by simply lowering the saddle. If the hamstrings are tight and the seat is high, the athlete may tilt the pelvis back to reduce the pull on the hamstrings. That in turn collapses the diaphragm and robs perfectly good breathing area, puts strain on the lower back and prevents the quads from getting up over the pedal and pushing harder. Lowering the saddle so that the knee bend at bottom dead center is 30-35 degrees rather than 25-30 degrees could reduce the pull on the hamstrings enough that none of that rotation occurs.

Kautz also suggested that a triathlete competing in an Ironman-distance event, he or she should consider using the aero bars to support the skeletal structure, rather than forcing the rider into a TT-like position in which the bars are often used to generate power by pulling hard on the bars. Most people simply cannot pull hard like that for 112 miles.

Kautz was adamant that all triathletes should have both a road bike and a triathlon bike. That road bike, said Kautz, is better for recovery rides, group rides and for climbing. But perhaps more importantly, road riding develops core strength, while riding in a triathlon position does not. Furthermore, a road bike is a far more effective means of improving fundamental skills like working through a group, descending and riding with no hands while changing layers or eating.

That very private numbness
The talk that really quieted the room down, however, was from Steven Schrader of the National Institute of Occupational Safety and Health (NIOSH) who talked about his studies of bicycle police and sexual health. NIOSH studies cycling because a union representing a bicycle police unit requested that the agency investigate health concerns, specifically erectile dysfunction.

First of all, it should be noted that bicycle police aren’t always in top condition and ride differently from most competitive cyclists. They carry up to 50 pounds of gear on their bodies and, therefore, on their crotches. Furthermore most bicycle cops spend around six hours a day in the saddle, often leaning with one foot on the ground, conversing with others. And much of the pedaling they do is low power, so the body is lifted off of the saddle less.

But competitive cyclists are not immune, insisted Schrader. He pointed to a quote from Lance Armstrong in a past issue of Outside magazine in which the seven-time Tour winner said, “It’s natural for your hands, feet, and crotch to fall asleep (while riding).”

“A body part going numb is not good – I don’t care if it’s your finger or your penis,” Schrader declared. “When your arm goes to sleep, your body doesn’t just say, ‘that’s just the way it is.’ No! It shakes it out and tries to get circulation and feeling back right away.”

Without going into the gory details, Schrader and his team did lots of studies with cyclists, including with different types of saddles and with studies of erectile frequency and duration while sleeping.

“Half of your penis inside your body. It’s a waste, but it’s there,” he pointed out, triggering a round of laughter in the audience, “and you’re sitting on it when you ride a bicycle.”

Schrader also studied female bicycle police and found issues with sexual health there, too. Schrader came away much enamored with “no-nose” saddles than with saddles with cutouts in them, which he said still could put pressure on important nerves and blood vessels. Clearly, this area needs more study, since most cyclists don’t necessarily suffer symptoms.

What a piece of work is man…
Richard Neptune, from the department of mechanical engineering at the University of Texas at Austin talked about musculoskeletal modeling of humans to give insight into bicycle setup and muscle function.

Neptune’s work involves building remarkable computer models of riders’ legs, showing bones and muscles as they move. They light up in different areas during activity to show when each muscle is firing and when it’s resting. While helpful in refining position, the technique can also instruct a rider on how to maximize pedaling efficiency, as it shows how one might generate power, while maximizing the number of muscles at rest. In one interesting study, Neptune discovered how very adaptable human beings are to changes in work load and conditions. While testing heart rate and blood pressure at an extremely high sampling rate, Neptune found that riders were able to quickly – and quite efficiently – change from round to oval chainrings.

“The muscle coordination adaptation happens almost instantaneously – in a few pedal strokes,” he says. “It feels different for longer, but that has to do with neuromuscular sensors.”

Early data – at the 10- or 15-second mark – showed a loss of efficiency with non-round chainrings. However, within a minute, there was no measurable difference in the power generated by the rider or in the level of effort put into the work.

All told, it was a remarkable conference and I look forward to seeing the quality of research presented at next year’s event.

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