Interesting Article For Our Cycling Audience

April 23, 2014 Posted by Dr.Chang

Cycling OrthoicsWe thought you may be interested in the following article from Lower Extremity Review (http://lowerextremityreview.com/article/cyclists-and-foot-orthoses-a-unique-set-of-challenges). Dr. Stewart Chang fitted Blue Ridge Foot and Ankle Clinic employee and local mountain bike racer Mark Smith (BRC Racing/CRC p/b Reynolds GM/Subaru) for carbon shoe orthotics recently. “I love these inserts. They are light and very stiff, providing me with optimal performance,” says Mark.  Mark also suffers from metetarsalgia. Therefore, Dr. Chang added an accommodation to the bottom of the orthotics allowing relief to the affected area of Mark’s foot.  “Before Dr. Chang added this pad to the bottom of my inserts, my feet would go painfully numb a couple hours into my ride.” Glad we could help Mark. Read the this article and let us know if you have any questions.

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Cyclists and foot orthoses: A unique set of challenges

Finding the right orthotic design starts with the space limitations presented by cycling shoes, but the challenges for lower extremity practitioners don’t end there. Factors to consider when prescribing foot orthoses include biomechanics, skill level, cycling discipline, and bike technology.

                                                     By P.K. Daniel

The cycling population tends to present less frequently with foot issues compared with other athletes, and that’s a good thing. Because, while finding the right design and materials for any patient is a challenge for practitioners who fit foot orthoses, when that patient is a cyclist those challenges are magnified. Factoring into the equation is how well a device will fit in the cyclist’s shoes, which typically don’t leave much room to maneuver. Orthoses have to be fairly thin. Material selection and other design elements, however, depend on the diagnosis, the cycling discipline, and the practitioner.

Extremely rigid carbon or polypropylene footbeds may be appropriate for elite track cyclists but may be unsuitable for a recreational endurance cyclist. Some practitioners use ethylene vinyl acetate (EVA), a low-cost foam that provides comfort with maximum contact but minimum pressure.

“Carbon is stiff, very stiff, sometimes too stiff,” said Happy Freedman, assistant to the director in the Prosthetics and Orthotics Service at the Hospital for Special Surgery in New York City. “I prefer it for higher-end riders. I prefer it for track riders who are riding shorter distances where power transmission is key. The flip side is it can be more fatiguing on the foot. Subortholyn [a semirigid plastic] is a little more forgiving and tends to be easier to manipulate after the fact, as well as during. That makes it work for a cyclist.”

Freedman, who is also coach emeritus for the Columbia University cycling team, cited a 2003 Foot & Ankle International study that found cycling shoes made with carbon fiber produced peak plantar pressures 18% higher than those of plastic design (121 kPa vs 103 kPa, a statistically significant difference).1 But competitive or professional cyclists suffering from metatarsalgia or ischemia should be careful when using carbon fiber cycling shoes, Freedman warned, because an increase in peak plantar pressure may aggravate these foot conditions.

A more recent study conducted by German researchers, however, found that carbon fiber can serve as a suitable material. It concluded that plantar pressures do not increase due to the stiffness of the carbon, and that individual customization may have the potential to reduce peak pressure in certain foot areas.2

Beyond stiffness

4ortho-iStock19862898-lrBut stiffness isn’t the only variable that needs to be considered, said Géza Kogler, PhD, CO, who is the director of the Clinical Biomechanics Laboratory in the School of Applied Physiology at Georgia Institute of Technology in Atlanta.

“Making a global statement that the stiffness of a material, in this case for an orthosis, is going to illicit higher peak plantar pressures in the foot is really misleading,” said Kogler, who teaches lower limb orthotics in the Master of Science in Prosthetics and Orthotics program at Georgia Tech. “The stiffness is only one characteristic. The interface geometry of the orthosis, such as one designed to be a total contact system [eg, a custom-molded orthosis], is likely to have a greater influence on plantar pressure redistribution than the stiffness of the material.

“Though I am not aware of any specific studies that can confirm this speculation, clinicians are cognizant that even rigid materials with the proper interface geometry [surface shape] can effectively redistribute foot pressures,” Kogler said. “Further studies are needed to clarify what role materials and shape contribute to controlling skeletal movements of the foot.”

Former professional cyclist Greg Bourque is the director of Peak Performance, an athlete testing facility at San Diego Sports Medicine. Given the shoe volume issue, coupled with the possibility of an individual’s foot swelling a half shoe size during the course of a day, Bourque elects not to use custom-molded orthoses for cycling. He prefers off-the-shelf inserts.

“With cycling, when it’s hot out, your feet swell, so I don’t like to have anything perfectly molded,” Bourque said. “In the beginning of the ride, it might fit fantastic, but you pound away a hundred miles in the hot temperatures your feet kind of change a little bit. They won’t be as comfortable. I just like stock [orthoses].”

He likes devices that provide different arch heights, have varying widths, and have some degree of cushion.

“Soft materials are best since [cycling] is essentially a non-weight-bearing activity,” said Soris Tribino, BOC, co-owner of BT Orthotic Labs in Farmingdale, NY, who also collaborates with the Hospital for Special Surgery’s Foot and Ankle Department. “It’s important that the materials have some cushioning and give to combat the forefoot overloading that commonly causes problems.”

By comparison, Freedman is not a fan of cushioning in cycling orthoses.

“You do not need to be padded for most cycling activities,” Freedman said. “It’s weight that’s not serving any purpose, and the cushioning effect can actually throw off the device in terms of tracking of the knee.”

Posting

Orthotic modifications, like posting, can positively affect cycling mechanics. Posting becomes important for sharing the load and creating the required alignment, experts say. Adding wedges can help align the biomechanics of the leg to maximize power. Wedging shims are fitted under the forefoot outer sole of the cyclist’s shoes between the shoe and the attached cleat. They can also invert or evert the shoe with the addition of wedges under the cleat.

“If someone has an injury or tendinitis in one particular area, I can post the orthoses in the forefoot in a different way to load another region of the foot away from that area,” Kogler said. “A wedge is probably one of the more effective features that we can include in an orthosis to achieve that.”

Tribino also noted that the bike needs to be factored into the equation.

“Many bike shops will actually use [off-the-shelf simple forefoot and rearfoot] posting to accommodate ankle and foot malalignments,” Tribino said. “It’s important, therefore, to communicate with the bike shop or fitter when designing the orthoses to ensure all in-shoe posting and cleat accommodations are taken into account.”

“[Posting] can put your knee in perfect alignment,” Bourque said, “and it can prevent injury because, typically when you pedal, all the power goes through the arch of your foot. If there’s no support there, you’re causing a series of problems because it’s a high-repetition exercise. Small adjustments over time make big differences.”

4ortho-iStock10555066-lrBecause volume, shape, and construction are factors with cycling shoes, Freedman doesn’t typically add to the orthosis.

“I tend not to do a lot of external posting of devices,” he said. “I try to keep the material as thin as possible. … I tend to keep them as light as possible.”

Freedman said if a cyclist wears orthoses in his or her everyday life, then he may need them in cycling. “If you’re wearing them for neuroma, then no in a cycling shoe. But if you’re wearing them for a flat foot and you need an arch, then you would wear them while cycling, too,” he said. Freedman also noted that you’d want a different orthosis than what is worn in daily life. “Most [everyday] orthoses weigh a bit more than I’d want in a cycling shoe.”

Because of the volume limitations of cycling shoes, such as a narrow toe box, some won’t accommodate regular shoe orthoses. Besides just fitting into a cycling shoe, biomechanical considerations include the correct arch height, the weight of the device, its width, and other factors.

“Cycling gait is different to a running and walking gait and the shoes are completely different in shape and rigidity,” noted Paraic McGlynn, chief executive officer and chief technologist at Cyclologic, a comprehensive cycling analysis solutions company based in Scottsdale, AZ. “As such, it is far more effective to have a dedicated cycling orthosis … to ensure correct fit and function.”

Floating points

Attached to the bottom of a cycling shoe is a rigid cleat designed to clip into the clipless pedal. Pedal technology, such as clipless pedals, rotational freedom, or float (the degree of mobility the foot has when it’s clicked into place) affects orthosis prescriptions.

Some pedal systems allow the rider to adjust the degree of float, as well as the direction in which the float occurs. For example, one pedal system offered for road bikes has a 15° release angle. It also has a lateral float of 6°, which means the rider’s foot can move 3° mediolaterally to the left or right.

According to industry experts, the total float range is 0° to 37°, with 90% of pedal systems having 3° to 9° of float. The direction of rotation can be adjusted completely in some pedal systems and can be rotated to bias the location of float in other systems. If a cleat were hypothetically “centered” on a shoe, it would have 50% of its total float in each direction.

Float is good for the typical cyclist because it essentially “allows” for poor cleat placement, said Daniel Swatton, product manager at Delcam, a Birmingham, UK-based supplier of advanced CAD-CAM solutions for the manufacturing industry, including orthotic solutions. He’s also an avid cyclist who wears orthoses.

“It’s becoming common in amateur cyclists looking to unlock extra power, as well as address pain issues,” said Swatton, who estimated that 90% of riders use pedals with float. “Float was created because in many cases it was better than simply locking the foot into place and allowing for no movement at the foot. Many riders were experiencing knee pain with fixed cleats, some due to biomechanical issues but mostly due to poor cleat placement and alignment.”

Too much float, however, can be problematic.

“The amount of float is very important and a good bike fitter will give you the right amount of float under each foot and minimize the risk for excessive float,” Swatton said.

In some cases excessive float can lead to knee pain, as the knee compensates for the instability at the foot. Excessive float can also negatively affect cycling performance.

“If the foot is not stable in the shoe, it moves in the shoe,” Freedman said. “If it’s moving in the shoe—and not necessarily in a controlled way—then the cleat is not floating on the pedal. An orthosis stabilizes the foot, keeps the arch from collapsing, and helps with better transmission of energy to the pedals with less stress on the joint.

“An unstable foot on a floating pedal is very inefficient,” he continued. “You don’t get good power transmission. You don’t get good release from the pedals because the foot is moving. So, if you have a flat foot that’s collapsing, the foot is moving in the shoe and not allowing the pedal to do what it’s designed to do.”

Tribino said the orthoses she recommends for cyclists may differ a great deal based on these variables.

“Again, it’s important to augment the orthoses for the individual patient’s symptoms, alignment, and biking equipment,” she said.

In general, more knee movement during cycling means more need for rotational freedom at the foot.

“If the orthosis corrects some of the knee movement, then it is common for less rotational freedom to be required,” McGlynn said. “Pedal axle length may also need to be modified to accommodate the appropriate stance width of the individual or to create space to accommodate extremes in internal and external foot rotation. The pedal and shoe challenges can be most effectively addressed in conjunction with a suitably qualified and experienced bike fitter.”

Not all bikes are alike

Tribino doesn’t subscribe to the notion that specific types of cycling (such as mountain biking, road biking, track cycling, or triathlon biking) affect foot orthosis prescription.

“The prescription is actually remarkably similar between these styles of biking,” she said. “While the activities differ, the motion does not, so the orthoses are more based on the specific patient.”

Other practitioners say they apply different prescriptions based on the different disciplines. Even the skill level of the rider—recreational versus competitive—can play a role.

McGlynn noted that each type of cycling has different power, shoe, and pedal dynamics, and, while the activity is broadly similar across all elements, there are also differences.

“For example, the contact point on a mountain bike pedal is tiny in comparison to the area on most road bike pedals,” he said. “If a client has acute metatarsalgia or a significant forefoot varus, their shoe-pedal combination may be more difficult to accommodate. These interdiscipline differences can change the materials used.”

Kogler noted one of the major differences with mountain biking is that, when ascending a mountain, the cyclist is out of the saddle and thus bearing more weight on the foot. This could lead to more injuries than would be the case for cyclists who spend most of their time seated.

Freedman also identified the differences he is confronted with.

“If I’m dealing with a track rider who’s very competitive, I will go with a carbon device for the length of the foot to get maximum power transmission, but their distances are much shorter than road riders,” Freedman said. “If I’m dealing with somebody who’s going to do stage racing and events upwards of one hundred-plus miles multiple days of the week, I want a device that is more forgiving and less fatiguing. If I have somebody doing cyclocross or mountain biking I may, depending on their needs, do a hybridized cross between a run and a cycling orthotic.”

Freedman also said he may add extra padding in the heel for shock absorption in certain cycling disciplines, such as cyclocross or mountain biking, in which the rider may get off the bike to run with it or to climb.

“It all depends on the needs and the skill level of the cyclist,” he said.

Bourque also cited the power transmission factor in track cycling, and noted that stiffer materials often facilitate greater power transfer for pedaling.

“Track is interesting because it’s all about power,” he said. “Everything is beefier in track. Track cyclists like to have things more solid. For track cycling you don’t want to lose any of your power going into the pedal from, say, squishing from a regular orthotic. If you could do a custom shoe that is basically molded to your foot, that would be ideal.”

Swatton noted that, since road riding requires the cyclist to be in the same position for many hours, the need for excellent biomechanics is acute.

“But with mountain biking, you are often in and out of the saddle [ie, in multiple positions], so orthotics have not been so widely needed or adopted,” he said.

How often cyclists need to replace their orthoses depends on a number of factors, including skill level, type and density of orthotic material, wear and tear, and changes in the foot structure. Freedman said it’s typically between 18 months and four years. Bourque recommends replacing orthoses every season for the everyday cyclists—and pro cyclists, whom he said average 20,000 miles or more a year, might change them more often.

“Many top-level athletes, including world-class performers, prefer lower density materials and are happy to replace footbeds yearly,” McGlynn said. “If this is the case, a duplication strategy should be well defined, as high-volume cyclists will detect the tiniest differences in orthosis construction.”

McGlynn also said that athletes who use higher density materials may need less frequent replacements but may require replacement of top covers or modifications made as shoes, equipment, or needs change.

“This depends on the mileage and style of biking,” Tribino said. “Typically, the higher the mileage, the more often the orthoses need to be replaced.”

Clinical indications

Experts say cyclists use orthoses for a multitude of reasons, including repetitive overloading, which can cause metatarsalgia, pain, and inflammation in the ball of the foot. Or they may be experiencing residual knee pain, chronic iliotibial (IT) band pain, patellar tendinitis, Achilles tendinitis, or hip or lower back discomfort because of their foot mechanics.

“The most common indication is metatarsalgia, from overloading the forefoot,” Tribino said. “The forefoot is particularly overloaded when bikers are in the standing position. Other common indications include planovalgus and cavovarus feet.”

Bourque also identified a high arch as a common indication for orthoses.

“When an [unsupported high] arch is pressed down—which you will do thirty-two thousand times over a hundred-mile ride—your arch flattens, your tibia rotates internally, and that’s going to lengthen your IT band. If you do that enough times, you’re going to develop IT band syndrome,” he said. “You’re going to have tracking issues. You’re just not going to be putting the power into the pedals that you want to. Your pistons aren’t going to be perfectly aligned. You really need to have your Achilles tendon in nice alignment and those pistons going straight up and down. They can’t be on an angle.”

An orthotic intervention can offset these issues. However, Kogler said wearing foot orthoses in everyday life doesn’t necessarily translate into needing them for cycling.

“It really depends on what the patient is wearing the foot orthoses for,” he said. “The reasons an individual may be wearing [them] for overground walking [are] totally not affecting things when you’re cycling. It’s very specific to the presentation of the symptoms. The load bearing in cycling is far less than in walking, for example. The major part of your load is in the saddle on the cycle, and therefore you’re not loading the foot to the same degree.”

The bottom line is that cycling foot issues are unique to this sport, and subsequently, so are the solutions.

“When you’re cycling, only the forefoot is being borne on the pedal for load transmission, and the hindfoot isn’t, which restricts load sharing to only the forefoot since loading of the hindfoot is relatively minimal,” Kogler said. “So the conventional techniques that work for standing, walking, and running are not applicable to cycling, creating a unique challenge for orthotists.”

P.K. Daniel is a freelance writer and editor based in San Diego, CA.

REFERENCES

1. Jarboe NE, Quesada PM. The effects of cycling shoe stiffness on forefoot pressure. Foot Ankle Int 2003;24(10):784-788.

2. Baur H, Hoffmann J, Reichmuth A, et al. Influence of carbon fiber foot orthoses on plantar pressure distribution in cycling. Sportverletz Sportschaden 2012;26(1):12-17.

3. http://lowerextremityreview.com/article/cyclists-and-foot-orthoses-a-unique-set-of-challenges

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