by Gary D. Hughes, Ph. D.
Gary Hughes is a bicycle fit specialist and owner of Bodacious Bicycles in Easton, MD. He offers the three levels of bicycle fitting mentioned in this article, and he repairs, rehabilitates and builds frames and complete bikes. He is also a Terry bicycle dealer. Gary can be reached at email@example.com.
It happens about this time every year – the thoughts of bicycling enthusiasts everywhere turn to France. For every year the Tour de France captivates us as the world’s most elite riders demonstrate nearly incomprehensible feats of human endurance, suffering, performance and power as they circumnavigate France in their quest for the yellow jersey. As the Tour showcases the very best in human conditioning techniques and bicycling technologies it motivates us to improve our own cycling performance.
Form, Fit and Function
Because different forms of bicycles perform significantly better on different types of stages (i.e. mountainous, flat, or time trial), each rider needs to use a number of different bikes to remain competitive over the whole course of the Tour. Imagine if you could select from an assortment of different length legs before setting out on a hike. You could put on longer legs for those days on the flats and then shorter ones for the mountains. Your friends could never keep up with you! More importantly, you could essentially eliminate the risk of repetitive use injury by ensuring that the applied loads never overly stressed your joints, tendons, muscles and bones. Of course realizing all of these benefits supposes that the right length of legs was selected for that day’s terrain and that the legs were sized to fit you perfectly. Otherwise this bionic entity couldn’t function optimally. You would find yourself moving awkwardly (wasting energy and possibly falling) and risking the development of a repetitive use injury (by repeatedly exerting forces on your body that it was not designed to support). This same logic applies when you strap on a bicycle. For it to function properly, it needs to have the right form and fit.
Striking the right balance takes real science. Hence, Tour teams extensively use wind tunnel tests and computer modeling to optimize the performance of each individual bicycle-rider system. The ultimate goal is create a fit that allows the rider to deliver maximum power and control the bike while still being able to maintain a highly aerodynamic position for the duration of the stage.
As riding enthusiasts, we too face tradeoffs. This starts with selecting the form of bicycle that will function best for the type of riding we will be doing. And selecting the right form nearly always requires some level of compromise. It also requires careful introspection. Why do you want to ride? It could be for some combination of relaxation, socializing, transportation, competition, travel, physical fitness, general health, or other reasons. Will the terrain be predominantly mountainous, hilly, flat, or mixed? Is the surface going to be dirt trails, country roads, the beach, or city streets? Is your riding style performance, touring or recreational? Answering these questions honestly and correctly will go a long way in helping you determine whether a road, hybrid, mountain, time trial, cross, triathlon, city, touring, cruiser or some other type of bike is best for you.
For any bicycle-rider system to function optimally, the bicycle must properly fit the rider. And the more riding you’re going to do, the more critical it is that your bicycle fits you correctly. That’s because with a properly fitting bicycle, you can enjoy riding until the point of exhaustion. You will want to spend more time and miles on your bike, because you’ll be able to enjoy the whole ride. Conversely, if you were to ride a bicycle that doesn’t fit your properly you’d find yourself becoming quickly uncomfortable, soon in pain, and working harder than you need to get to where you want to go.
The key to enjoying a lifetime of bicycling is to ensure that a good fit exists between you and your bicycle.
Bicycle fitting is an inexact science. There is no set of formulas that can completely define the ideal size and contact interfaces for any given rider. Rather, it is largely an empirical process that works by progressively approaching a perfect fit. The objective is to get the fit close enough to perfection for the rider to be able to repeatedly enjoy her cycling experiences and to ensure that she is efficient and safe in doing so.
Three parts of the body contact the bicycle: hands, feet, and bottom. Bicycle fitting involves determining and setting the median positions of these contact points relative to one another in space so that the rider can perform optimally. In other words, this defines how far the handlebars are in front of the saddle as well as how far above or below they are. It also sets how far the pedals are from the saddle. More specifically, this position defines how far the saddle is above and behind the axis around which the pedals rotate (bottom bracket). Taken together, the positions of these three points provide necessary, but not sufficient, information for specifying the proper frame size.
Each of the three interfaces needs to be defined, but they cannot be defined independently of one another. For instance, how a cyclist will orient herself on a bicycle saddle depends, among a long list of other things, on how far she is leaning forward, and that depends on how far forward the different contact points for her hands are on the handlebars. This interdependence means that if you want to change the handlebars, you may find that you also need to change the saddle.
The first step in fitting a saddle requires selecting a suitable one. This selection process should start by narrowing the options under consideration to only those that will support the rider without putting undo pressure on sensitive or vulnerable parts of the anatomy while allowing the rider to pedal naturally and without chafing. Comfort can then be considered, but it should be assessed in the context of riding style. For example, cushy saddles might feel more comfortable than firm ones on short rides, but perceptibly less so on longer rides. Other factors to be considered include whether the saddle needs to be tilted and whether the seatpost supporting the saddle should be rigid or suspended.
Handlebar selection presents a similar number of options. This too starts with selecting the right category of handlebar: mountain, road, aero, etc. Within each of these categories, there are options. For instance, with road bars there are different widths, reaches, and drops to consider. It is also important to consider where to position the brake levers and gear shifters. Then there are the pedals. Again, there are a lot of options to consider. Some options deserving of consideration include the length of the crank arms (this defines the diameter of the pedaling circle), how far the pedals are mounted from the center of the frame, the type of pedal, the amount of float, and where cleats are mounted on the rider’s shoes.
Finally, there is one other consideration that a bicycle fitting must address in setting up these contact interfaces: the symmetry of the rider. Is one arm significantly longer than the other? Is one leg longer than the other? Or does one or both of their feet exhibit some degree of forefoot varus? Or is there some other anomaly? If so, these conditions need to be accommodated.
Repetitive Use and Repetitive Use Injuries
Bicycling is an athletic activity in which you repeat the same biomechanical motion over and over again for the entire ride. How many times you repeat that motion depends on how far you ride, the terrain you are traveling over, and whether you tend to mash your pedals or spin them. Although both mashing and spinning expend the same amount of energy to maintain a given bicycling speed, they exert different loadings. Mashers pedal slower but push down on the pedals harder with each stroke; spinners pedal faster but push less hard on the pedals with each stroke.
To get an idea of the range of numbers involved, imagine two riders both riding Terry Isis Pros on this year’s Wild Goose Chase Metric Century and averaging 16 mph. Since the course was flat and ignoring the wind (which is of course like ignoring the proverbial 800-pound gorilla in the room), it might be reasonable to assume that both riders stayed in the one gear for the duration of the ride. Let’s say the masher stayed on her large chain ring (50 teeth) and a middle cassette cog (16 teeth). Her cadence would then have had to be just over 60 rpm for her to maintain 16 mph. By the time she finished, she would have applied over 14,700 pedal rotations. In contrast the spinner would have likely stayed on her small chain ring (34 teeth) and a middle cassette cog (17 teeth). With that gear selection, her cadence would have had to be just below 100 rpm and she would have needed over 23,000 pedal rotations to finish.
Both, either, or neither of these riders could develop a repetitive use injury. Imagine sanding a piece of wood. You can remove about the same amount of material with fewer strokes by applying slightly more pressure. That’s analogous to what happens when a load, however small, is repeatedly applied in other than the way your body is built to support it. Body parts rub against other body parts or the bike in ways that cause irritation. And continuing to repeat the offending motion will cause the irritation to progressively intensify as it continues to be re-aggravated before it can heal. Left untreated, this is likely to grow into a chronic or serious health problem.
Is there a lower limit to the onset of repetitive use injury? Probably, but it’s substantially below the numbers derived above in the Wild Goose Chase example. Consider that repetitive use injuries can occur from walking, and that the average person takes approximately 4,000 steps a day. The masher in the previous example would have surpassed that number of pedal strokes before reaching 11 miles. And once an irritation has formed, it takes but a few additional repetitions of the offending motion to re-aggravate it.
The best way to avoid repetitive use injuries and get the most pleasure and fun out of your time on the bike is to have a bike that fits you properly. And the best way to ensure the bike fits you properly is to visit a certified bike fitter, who can assess your needs and riding style and adjust your bike to meet your specific needs.
Adjusting the Bicycle to Fit You
In the foreword to Andy Pruitt’s Complete Medical Guide for Cyclists, Chris Carmichael describes how, as a young racer, he had found himself suffering from severe knee pain. As a result of this he visited Andy Pruitt, who diagnosed him as suffering from iliotibial (IT) band friction syndrome and prescribed a treatment that quickly stopped the pain. However, what impressed Chris Carmichael most was not that Dr. Pruitt alleviated the pain, but that he determined and corrected the source of Carmichael’s IT band affliction—his riding position. After Dr. Pruitt showed him how to modify his riding position, Carmichael never again suffered from IT band friction.
That is exactly the sort of experience I get to witness regularly in my work as a fitting specialist. Clients are typically experienced cyclists with thousands of miles logged. But either they can’t seem to get comfortable on their bicycle or they are beset with lingering injuries. Surprisingly, a quick fitting session often uncovers a serious problem with their current fit. Occasionally there are telltale hints, like a saddle angled up or down by 30 degrees, or handlebars wrapped in three-inch-diameter pipe insulation. Other times, it takes a bit more detective work. In either case, clients are typically amazed that by simply changing some of the components on their bicycle or inserting a spacer under one of their cleats, they are suddenly able to start riding pain free again.
Of course, sometimes the fit analysis leads to the conclusion that an altogether new bicycle is warranted. But even that is a relatively minor cost to pay for pleasurable, pain-free, efficient riding.
Benefits of Fitting for Recreational, Touring and Performance Cyclists
The ultimate goal of rectifying fit problems is to keep people from developing repetitive use injuries in the first place. And the real challenge here is getting recreational and touring cyclists to consider getting fitted before buying and extensively riding a bicycle. Imagine ordering clothes without knowing your size! Yes, you could hire a tailor to take in the pants or a cobbler to stretch the shoes, but wouldn’t it be a lot easier to buy the correct size to begin with? Unfortunately, recreational and touring cyclists often feel that they’re not into bicycling enough to justify getting fitted. Worse yet, they are more likely to attribute a repetitive use injury to their lack of training—and often try to grit their way through the pain, which can exacerbate the injury.
They couldn’t be more wrong! Although it’s counterintuitive, a poorly fitting bicycle will become uncomfortable and potentially injurious for a recreational rider in fewer miles of riding than it will for a touring rider; and touring riders will become uncomfortable sooner than a performance rider. That’s because a performance rider applies more energy to the pedals. This tends to lift more of the rider’s weight off of the saddle and handlebars as well as forces the rider to lean forward more in order to maintain a smoother pedaling motion. In contrast, a recreational cyclist tends to sit more upright and supports more of their weight with their hands and bottom. And it’s critical to ensure that this weight is supported comfortably, as well as that this position allows the rider to use their natural pedaling motion.
It is precisely because of this phenomenon that two riders with exactly the same physiques and conditioning can require their bicycles to be set up differently: one may enjoy performance cycling and the other recreational.
Types of Fitting
At Bodacious Bicycles we offer three levels of fitting. The first level involves taking a series of static measurements that will let you know if your current bicycle is approximately right for you. Alternatively, it could tell you whether a bicycle you are considering to purchase is likely to fit you. Basically, it gives you a good starting point. This may be all you need if you find riding your bicycle to be comfortable and responsive. If that is not the case, however, then a dynamic fit is in order.
A dynamic fitting involves taking another series of measurements, but this time while you are pedaling. Going through this additional level allows your flexibility, riding style, and any existing conditions to be assessed directly rather than inferred from an interview process. By the end of this process, enough information will be generated to let us confidently modify the setup of your current bicycle or specify the geometry and setup of a new one.
The final fitting level, performance fitting, is less about comfort and more about responsiveness and power. It focuses on how changes in your position and/or cadence affect your power output. In short, it provides a laboratory and the tools necessary to hone your performance.
A short description of each of these fitting levels follows.
The first level, static fitting, has two parts to it. The first part involves acquiring your skeletal measurements and ascertaining information about any pre-existing conditions and your riding style and expectations in addition to any issues, concerns, or complaints you may have about your current bicycle. This data is used to generate your developmental fit parameters and to recommend a particular bicycle geometry that will not only fit you well, but is also well suited for your riding style. The second part of the static fitting process involves measuring your bicycle and assessing its range of adjustability. A comparison of these two sets of data is then made to determine how well your bicycle fits you and how it might be adjusted to fit you better—or whether you should consider changing certain components, or even moving to a totally different bicycle. Every bicycling enthusiast should go through at least this “biomechanical” level of fitting to ensure her bicycle can deliver mile after mile of healthy and enjoyable riding.
The second level of fitting, dynamic fitting, builds upon and further refines the recommendations of the static evaluation. It also involves two parts. The first part has you riding your current bicycle on a stationary trainer. Measurements are taken to define the range of angular motion of your hips, knees and ankles. In addition, observations are made as to how you naturally posture your head and neck, arms, and lower and upper back, as well the degree to which you rock your hips while riding. The second part of this process gathers the same measurements and observations, only this time it’s on an infinitely adjustable bicycle simulator. The simulator is initially set to the fit recommended by the static assessment. These settings are then incrementally refined to dial in where you feel most comfortable. It also allows you to try different saddles, handlebars, and crank arm lengths. I always recommend this second level of fitting to anyone that is experiencing continuous and lasting discomfort when riding her current bicycle. It’s also best to get this level of fitting to try out new geometries before changing any components on your current bicycle or purchasing an altogether new bicycle — as might have been recommended by the static assessment. Dynamic fitting takes the guesswork out of your purchases, and by buying the right-size component the first time you almost always save money in the long run.
The final fitting level, performance fitting, is intended for people looking to improve upon their personal best performance — whether for a race, time-trial, club ride, century ride or just a loop around their neighborhood. Like the dynamic fit process, it involves riding both your current bicycle and the bicycle simulator; however, this time instantaneous and sustained power output are measured as a function of different riding positions and cadences. The performance fitting process starts on the simulator, where data can be gathered that will tell you how subtle seat and handlebar/aerobar adjustments affect your power output. The same thing can be done to evaluate the effect of different crank arm lengths and handlebar widths, drops, and reaches. It can also give insight into how you should position yourself for optimal power output in climbing, descending, and riding on level ground. Once this data is acquired it is then used to fine-tune your bicycle for a particular event. The performance fit process concludes with us monitoring your power output while riding your bicycle on a stationary trainer under simulated race/ride conditions. This allows us to precisely dial-in every adjustment on the actual bicycle you will be using for that particular event.