ABCs of bike fitting

Lifted off bikefitting.com

INTRODUCTION

In the last few years more and more attention in the cycling sport has been paid to coaching and supervision of the cyclist. So much progress has been made, particularly in the field of training and nutrition, that the physical performance has nearly reached its optimum.

In order to further improve the efficiency of the cycling movement, optimizing the position on the bicycle is an absolute prerequisite. The ultimate aim is to achieve a position of the cyclist on his bicycle which is as efficient and as aerodynamic as possible.

If efficiency were the only factor demanding attention, it would be fairly simple. During this last decade, the cycling sport has evolved from an endurance sport into a power-endurance sport. The influence of biomechanic and aerodynamic research is gaining importance. The goal is to find a cycling position in which power is maximally converted into motion.

Scientific and empirical research has shown that a correct position on the bicycle is determined by several factors.

The matrix that illustrates the correlation between these factors consists of the following elements: friction, efficiency, power maximization and comfort.

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In reality, however, the results of this research are not always used to its full extent. It is apparent that many cyclists, and not only the recreational cyclists, still adopt a very poor position on their bicycle. This clearly illustrates that the vanguard of the cycling sport has so far failed to appreciate the effect and use of biomechanic and aerodynamic research.

A proper sitting position on the bicycle has other advantages, also. Cyclists are regularly confronted with injuries, and cycling tourists face physical complaints in large numbers. These injuries and complaints are caused by deviations in position or by an incorrect position on the bicycle. Optimizing the sitting position on the bicycle prevents the occurrence of injuries

It is clear that the four factors mentioned above not only influence but also negatively affect each other. For example, the average cyclist experiences a deep aerodynamic position of the upper body as anything but comfortable

RESISTANCE

The resistance experienced by a cyclist consists of three components:

Frictional resistance.

This resistance occurs when layers of air pass each other at different speeds and thus influence each other. The air immediately surrounding the cyclist moves past the environmental air, which results in resistance

Shape resistance

This is the most important kind of resistance. The air in front of the cyclist is pressed together, but behind the cyclist the air is more or less sucked away. This leads to a difference of pressure in front of the cyclist and behind him, which in turn leads to an opposing force.

The extent of resistance is determined by the size of the frontal surface which is perpendicular to the direction of movement and the shape of the body, also referred to as streamline. This is the measurement that indicates to which extent the air is enabled to glide gradually past the cyclist and his bicycle.

Wind tunnel experiments have shown that the cyclist is responsible for 75% of the air resistance, and the bicycle for 25%. Some researchers assert that a streamlining of the bicycle is only meaningful at speeds of more than 56 km/hour.

It is obvious that a good aerodynamic position on the bicycle depends on many factors (such as speed) and can differ from individual to individual. Certainly for riding a time trial or the world hour record, an individual assessment of the position on the bicycle is of vital importance. As a rule, a horizontal position of the torso is the most advantageous position when it comes to matters of air resistance. This implies that the upper part of the hip and the acromion must be in a horizontal line. At a deviation of only 10 degrees upwards, the speed decreases with an average of appr. 1 km/hour, or 2.5% (Van Ingen Schenau 1985).

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From High-tech Cycling (1966). Although this diagram is in principle a correct reflection of the resistance, it seems that the power output is relatively high

EFFICIENCY

The formula makes it is clear that efficiency can be increased by increasing the physical effort and, at the same time, using the same amount of energy, or by using less energy during a given physical effort. The advantage of this formula is that it takes into account the minimum amount of energy required to move the legs (i.e., the energy required to cycle without any resistance). In this way, the efficiency of the muscles is accurately determined because the energy needed to keep the body in motion is deducted from the total use of energy. How is this formula applied? The use of energy can be measured in a laboratory through the intake of oxygen. The intake of one liter of oxygen (not air) equals the use of 5 kcal. In other words, a given person first starts to cycle without any resistance and afterwards with a certain resistance. In both cases, the intake of oxygen is measured, after which the results are put into the formula. Physical effort is expressed in Joule. In order to convert Joule to kcal, the figure expressed in Joules has to be divided by 4.19.

Another method to determine the efficiency is the cost function. This is a mathematical expression which provides a description of a certain physical effort by giving it a numerical value. Or to put it more simply, the cost function describes the relative efficiency of a movement with only one number. The determination of this cost function is based on the moments in the joints during the cycling movement. It is an established fact that these moments correlate directly with the tension in the muscles. Subsequently, the tension in the muscles is a criterion for the efficiency of a contraction. If the sum of the moments in the ankle, knee and hip is minimal, then the position in which this is the case is the most efficient one.

The formula mentioned above, however, does not take into consideration one important element which is inherent in sport, in general: the aspect of competition. This implies that the distances are covered at a relatively high speed or, alternatively, within a certain time frame. When we introduce the time element into the formula, we no longer speak of physical effort, but of power. The best cyclist will be the one who burns the most calories within a given time frame, thereby taking for granted that all cyclists expand the same amount of energy at a certain speed. In reality, this is not the case because not all cyclists adopt an equally efficient position on the bicycle. So there are a number of cyclists who use up more energy than others in order to arrive at a certain speed.

What are the factors on which efficiency depends when looking at it from a biomechanical perspective? Gonzales and Hull (1989) conducted a survey into this matter, and they came to the conclusion that there are five factors that determine the efficiency in cycling. In their research they also come to the conclusion that these factors are interrelated. A logical result of this conclusion is that these factors should be adjusted accordingly, in order to arrive at an optimal combination. Hence the use of the term multi-variable measuring method.

CADENCE

The pedaling frequency is the number of rotations of the pedal per minute. Research into the optimal pedaling frequency has been extensive. Already in 1929, Hartree and Hill indicated that there had to be an optimal pedaling frequency. When a cyclist pedals too slowly, energy is taken away from both power, as well as duration of contraction. On the other hand, if a cyclist pedals too quickly, energy is lost to overcoming internal resistance in the muscle. So there has to be an optimum; however, Hartree and Hill failed to indicate where this optimum was to be found.

In other surveys, the lowest level of oxygen intake was used as a criterion. Gregor (1986) presented an overview of these studies. In most instances, the result was somewhere between 33 and 80 rotations per minute (rpm); however, in reality, most cyclists invariably choose a frequency that lies between 90 and 110 rpm. At first it was believed that this difference could be explained by the effect of training, but this hypothesis lost ground as a result of tests conducted by Boning and associates (1986). He tested both trained as well as untrained test persons and came to the conclusion that, in spite of the greater effort that untrained test persons experienced when resistance increased, the optimal pedaling frequencies did not change.

A few years earlier, however, Hagberg (1981) made an interesting discovery. He noticed that, when deducting oxygen usage in cycling without resistance from the oxygen usage in cycling with resistance, the optimal pedaling frequency shifted towards 100 rpm.

Redfield and Hull (1986) had an explanation. They used the sum of the torques in ankle, knee and hip as a criterion (Cost function, see diagram). This was calculated in the function of the pedaling frequency, and it appeared that it was the lowest between 90 and 100 rpm. This corresponds quite well with the pedaling frequency of cyclists in everyday reality.

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In other research, Hull (1988) looked into pedaling frequency in more depth. He made use of a combination of joint torques and tension in the muscles in relation to the pedaling frequency. In this survey an optimum was also found at a frequency between 90 and 100 rpm. Apparently, the tension that arises in the leg muscles during cycling is the most decisive factor for the pedaling frequency. This shows that already in 1929 Hartree and Hill came very close to explaining why lower pedaling frequencies were far from ideal.

Cadence in real live:
The list, below, with all the postwar world hour records illustrates that for this specific aspect of the cycling sport a somewhat higher pedaling frequency is preferred; the average here is 103 rpm

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CRANK LENGTH

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The second variable is the crank length. This is the distance from the heart of the bottom bracket axle to the heart of the pedal axle. Contrary to the pedaling frequency, the crank length cannot be altered during the cycling process. It is of the utmost importance that the crank length is adjusted very precisely to the physical characteristics of the cyclist. In addition, a given crank length is only optimal for one specific pedaling frequency. In other words, it is of very little use to determine an optimal crank length if the pedaling frequency is not taken into consideration. Hull and Gonzales (1988) have been looking for an optimal combination between these two variables. In order to indicate that both the pedaling frequency and the crank length have an influence on the power exercised on the bottom bracket axle, they suggest the following formula:

P = Fn.Lc.ȏ
P: power exercised on the bottom bracket axle
Fn: effective component of the power exercised on the pedal
Lc : crank length
ȏ: angle velocity of the crank arm

When the pedaling frequency increases during a continuous and effective power exercised on the pedal and with a fixed crank length, the power exercised on the crank spindle will increase. The same thing happens when the pedaling frequency is kept constant but the effective power increases. On the basis of this comparison it can be concluded that the pedaling frequency should be as high as possible and the crank length as long as possible; however, as stated earlier, the pedaling frequency must stay within certain limits in order to reach its optimum. Because pedaling frequency and crank length are interrelated, the crank length must also stay within certain limits.

Because pedaling frequency and crank length are interrelated, the crank length must also stay within certain limits. Earlier research showed that the longer the crank, the lower the optimal pedaling frequency. On the basis of this fact, each individual cyclist can make a choice. But there is a third variable that must be taken into account, and those are the physical dimensions in general, and the length of the legs in particular. Hull and Gonzales (1988) came to the conclusion that the optimal pedaling frequency becomes lower and the optimal crank length gets longer when the length of the legs increases. This can be explained by pointing at some of the principles of the way the muscles work.

Why does somebody with longer legs need longer cranks?
Muscles have a certain optimal reach within which they can exercise the most power. This reach gets wider when muscles get longer. In order to use this optimal reach to its full capacity, the length of the cranks must get longer, so that the angles of the joints get larger and, as a result, the length of the muscles can vary over a larger distance. Hull and Gonzales (1988) found an ideal combination for a test person with a length of 1.77 meters: a pedaling frequency of 110 rpm and a crank length of 145 mm. This crank length deviates quite substantially from the standard crank length of 170 mm. When calculating the cost function for both crank lengths, a difference was noted of 2.4%. However, it should be noted that Hull and Gonzales derived their results from models rather than from experiments.

The diagram shown below presents a more pragmatic approach and gives an indication of how crank length relates to body length (Burke 1996).

If the crank length increases and the pedaling frequency remains the same, the muscles will contract over a longer distance as a consequence of a larger circular movement of the legs. However, this should take place within the same time span, which means that the contraction speed of the muscles will increase. At a higher contraction speed, the extent in which power can be exercised in the muscles will decrease (Hill, 1938).

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SEAT ANGLE

The seat angle is the decisive factor for the position of the saddle, the so-called saddle fore and aft placement..

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According to Gonzales and Hull this saddle set back position ranks third in importance when it comes to efficiency. Just as with the crank length, the seat angle is a factor that cannot be altered during the process of cycling. Because the seat angle directly influences the efficiency, it is of vital importance to determine the seat angle before purchasing the bicycle. The seat angle is the angle that is made by the seat tube and an imaginary horizontal line.

The most striking example of an adapted seat angle is probably the so-called American triathlon position. Here, the angle tends towards 90 degrees, whereas a standard frame angle measures 72 to 75 degrees. The triathletes claim that for them this position is more comfortable. They can ride their bicycles more efficiently, they can exercise more power, and the shift from cycling to running proceeds more naturally; however, solid evidence for these assertions has not yet been provided.

What is also striking is that cyclists assume different positions on their saddles when riding different tracks. When riding downhill, they tend to shift towards the back of the saddle, whereas during climbing they move somewhat forward on their saddle. This might lead to the conclusion that changing positions on the saddle has a mechanical or metabolical advantage.

How to determine the optimal seat angle? When the saddle is adjusted at the correct height and pedal and crank are positioned horizontally, the perpendicular line should go from the knee cap straight through the pedal axle. Research shows that there is increased stability of the saddle position when this perpendicular is appr. 2 cm behind the knee cap.

Determining the seat angle by only measuring the upper leg-length does not suffice. It should be noted that measuring of the seat angle should be conducted while the cyclist is positioned on the bicycle. The sitting position on the saddle is strictly individual, as it is influenced by the width of the pelvis and the shape of the saddle. The position on the saddle determines the position of the knee during the cycling movement; thus, the position on the saddle influences the seat angle.

The standard-seat angle-geometry, at which large frames are equipped with a shallow seat angle (72 degrees) and small frames are equipped with a shallow seat angle (75 degrees), presupposes that people with longer legs automatically have relatively longer upper legs than persons with shorter legs. The following diagrams illustrate that this presupposition is incorrect. Diagram 1 illustrates the relation between total leg length and upper leg length with students of the Technical University of Delft (Molenhoek, 1994). These statistics clearly show that there is no difference in the relation total leg length / upper leg length between people with longer legs and people with shorter legs.

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Diagram 2 shows the seat angle measuring results of 1028 persons according to the bikefitting.com measuring system. In this group there were 39 males with an inner leg length of less than 800 millimeters and 39 with an inner leg length exceeding 960 millimeters. Also included in this group were 4 females with an inner leg length of less than 700 millimeters and 6 with an inner leg length exceeding 860 millimeters. Generally speaking, this correlates with categories p5 and p95 of diagram 1.

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Diagram 3 shows the standard seat angle for different frame sizes of four frame constructors who (still?) take the incorrect supposition as described above as their starting point.

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SADDLE HEIGHT

The saddle height is the distance from the upper part of the saddle to the heart of the pedal axle (see illustration size 1).

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The adjustment of the saddle serves to enable the muscles to work optimally in the longitudinal reach. As there is only one optimal longitudinal reach, there is only one optimal saddle height. Most of the methods used at present to determine the correct saddle height are far from optimal. We will briefly discuss a few of these measuring methods.

First there is the so-called heel-method. The heel of the shoe is placed on the pedal and the saddle is adjusted at such a height that the leg is stretched while the pelvis is still in horizontal position. So far no evidence, empirical nor scientific, has been found to justify this measuring method. More importantly, this method does not take into account the fact that the modern cycling or racing shoe has a heel jump. In reality this means that, as a rule, with this method the saddle is adjusted too low.

The second method was developed by Claude Genzling. During the Tour de France of 1978 he measured the body sizes of the cyclists and the respective adjustments of their bicycles. On the basis of these measurements Genzling arrived at the following conclusion: the saddle height ( the distance from the heart of the bottom bracket to the upper part of the saddle) = 0.885 x inner leg length. Two critical remarks, however, should be made about Genzling's conclusion. Nowadays the adjustment of the saddle height demands a different approach, given the fact that in the course of time the cycling sport has evolved from endurance sport to power endurance sport. Secondly, the Genzling formula takes a relative size (see saddle height illustration size 2) and an absolute size (crank length) as starting points. In this method, an incorrect crank length would lead to an incorrect saddle height because the saddle height is the distance from the saddle to the pedal axle (see definition above). In other words: this method is inconsistent.

A third method is more scientific and was developed by Nordeen-Snyder (1977). In determining the optimal saddle height, the use of oxygen was taken as a starting point. On the basis of experiments it was concluded that the ideal saddle height corresponded with 1.05 x trochanter height; however, this method does not mention if the thickness of the sole and the height of the pedals are taken into consideration. Depending on the pedal-shoe system that is used, notable differences in saddle height can occur ( illustration size 1). A practical disadvantage is that it is very difficult to determine the trochanter height. Other surveys based on the same method determined the saddle height at 1.09 of the inner leg length (Hamley & Thomas, 1967).

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Another method (Homes, Pruitt & Walen, 1994) starts from the angle of the knee. When the pedal is in its lowest possible position, the knee should be able to bend 25 to 30 degrees. This method is only applicable when a global indication of the saddle height suffices. Other surveys, however, make clear that an exact determination of the saddle height can have major consequences for energy expenditure.

Gonzales and Hull (1989) showed that an optimal adjustment of the bicycle depends on more than one variable, and that these variables are correlated and interrelated. They are in favor of a multi-variable measuring method because the single-focus approaches described above are too limited and do not lead to individual optimization. However, no general conclusions and recommendations can be made.

FOOT POSITION

The last variable, according to Gonzales and Hull (1989), is the longitudinal position of the foot. This position is mainly determined by the adjustment of the shoe cleats. For this variable there is one rule, which stipulates that the shoe cleat should be adjusted in the longitudinal direction of the foot in such a manner that the ball of the foot (the metatarsal head) is exactly above the middle of the pedal axle (Mandroukas, 1990). This adjustment of the foot stimulates the process of "ankling", which results in a regular cycling pace and an effective position of the pedal in relation to the position of the crank (Haushalter 1994).

When the ball of the foot is placed in front of the pedal axle, the effective leverage from the ankle to the pedal axle is reduced. This way it is easier to stabilize the foot on the pedal, and it leads to a decreased tension on the Achilles tendon and the calf muscles. Some triathletes and time trial cyclists choose this option because the increased stability of the foot enables them to shift into a higher gear. The possibility of achieving higher pedaling frequencies is limited by this adjustment and the ankle pattern is a lot less regular, especially in the upper and lower positions, because the possibility of deviation in the ankle joint is limited.

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When the ball of the foot is placed behind the pedal axle, the effective leverage is enhanced, making it more difficult to stabilize the foot on the pedal. The consequence of this position is that the Achilles tendon and the calf muscles are under increased strain in order to maintain sufficient rigidity of the foot. This method is sometimes adopted by track cyclists because it enables them to achieve a higher pedaling frequency.

The position of the foot (shoe) on the pedal not only has consequences for the possible occurrence of injuries, particularly of the knee, but it also affects the efficiency of the pedaling movement. adjusting shoe cleats, one often tries to realize the most natural position of the feet on the pedals; however, when doing so, one should bear in mind that cycling with feet in a fixed position is an imposed movement. This means that the circular movement of the pedals is imposed on the cyclist, and the cyclist has no choice but to adapt to the drive mechanism of the bicycle.

When shoe cleats are adjusted correctly, the knee remains in the axle that runs from the hip joint to the ball of the foot during the cycling process. Every deviation, both inward as well as outward, results in loss of effectiveness.

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POWER MAXIMIZATION

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The power that is exercised exactly under a 90 degrees angle on the crank is effective.

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The red line represents the effective pedal load during 1 rotation, starting at the top dead point.

The purpose of power maximization is to position a cyclist on his bicycle in such a manner that the percentage of effective power yielded by the cyclist is as large as possible. Only the power which is exercised vertically on the pedal arm (see figure 1) is effective. When the pedal is positioned at the lowest or upper 'dead' point, the effective power that results is practically negligible (figure 2). This means that especially when the crank is in the 90 degrees position (maximum leverage), the adjustment of the bicycle must be such that the power that is exercised, is exactly under a 90 degrees angle on the crank. This also means that the forward and backward adjustment of the saddle plays an important role. If the saddle is placed too much in a backward position, it will result in a pedal position that corresponds with position 2 of figure 1. If, on the contrary, the saddle is placed too much in a forward position, the pedal will correspond with position 3 of figure 1. The blue arrow represents the power that is exercised, green represents effective power, and red represents loss of power.

It goes without saying that the most efficient position and the position that leads to the most effective exercise of power does not necessarily have to coincide. Where exactly to find the optimum between the two is still a matter of research and debate. This optimum is likely to vary, depending on the cycling event and the type of cyclist. For cycling competitions lasting more than one day, the emphasis tends to be on an efficient position on the bicycle, whereas in time trials the aspect of power is given a higher priority. Cyclists with a relative "slow-twitch" physiology of the muscles will choose for power, while cyclists with a "fast-twitch" muscle physiology are more likely to opt for suppleness and flexibility

Yet, it is justified to draw some conclusions based on empirical evidence. Generally, it can be asserted that in case of an increase in saddle height, the extent to which power can be exercised will increase; however, this will lead to a loss of speed of the cycling movement (cadence) which, in turn, determines the level of efficiency of the cyclist. In other words, a high position of the saddle is only recommended in short-term efforts that require a lot of power such as off-road cycling, mountain biking and uphill time-trials. A high position of the saddle very often leads to use of heavier gears which, in the long run, could lead to complaints and injuries. The same can be said about crank length. Longer cranks lead to more power, but they decrease the number of pedal rotations per minute. For the moment the aspect of power maximization will remain a matter of trial and error, with biomechanical elements as well as elements of injury prevention and physical straining.

Research into power maximization in the cycling sport has led to the development of the ellipse-shaped chain-wheel. The purpose of this ellipse-shaped chain-wheel is to increase the angle speed of the crank when it is in the lowest or upper 'dead' point at a constant chain speed. The moments in the pedaling cycle that yield little effective power will thus be made shorter; however, research has never been able to prove the effectiveness of these chain-wheels and, as a consequence, they are no longer used in competitive cycling. It is assumed that the element of muscle coordination is decisive; trained cyclists only want to exercise a steady and regular pedaling movement.

In the last few years the cycling sport has evolved from an endurance sport to a power endurance sport. In the 1940s and 50s it was common to use gear ratios of 49 x 17. At present, gears of 53 x 11 or even larger are no longer exceptions. In order to use these gears over a longer period of time, it is essential that the power that is supplied is used as efficiently as possible.

COMFORT

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Comfort is the least investigated factor in the matrix. This parameter is predominantly based on rules of experience and is subject to years and years of trial and error. Even the most well-known manuals, such as Science of Cycling, present the reader with a number of general statements that provide little basis for a more systematic approach. In reality, the aspect of comfort is taken into consideration only when the adjustment of the bicycle leads to inconveniences or complaints.
We will discuss a number of aspects that deal with comfort, taking the parts of the body which actually make physical contact with the bicycle (i.e., saddle, handlebars, pedals) as our starting point. It should be noted that these three parts of the body are of crucial importance in the adjustment of the bicycle, rather than the size of the frame. Many cyclists and bicycle dealers are fixed on the size of the frame, and the size of the frame only. The frame geometry (which is more than just the size of the frame) is only important when adjusting the bicycle, in order to get the three contact parts of the body in the right interrelated proportion. This aspect is irrespective of the fact that the frame geometry can have consequences for the cycling properties of the bicycle.

The saddle.

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A saddle should fit comfortably. Having said that, this is the most difficult aspect when trying to adjust the bicycle. On the one hand, the width and shape of the saddle depend on the distance between the seat-bones and the shape of the pelvis. The larger the distance between the seat-bones and the rounder the pelvis, the wider the saddle should be. On the other hand, the width of the saddle also depends on the position of the upper body on the bicycle. When sitting on the bicycle with a very curved spine, a narrow racing saddle is more comfortable and more functional ( grating of the inner legs). When sitting upright, a wider saddle is generally more comfortable (Van Hulten, 1999). As far as is known, no practical measuring method has been developed yet which takes into account both width and shape of the saddle, as well as the position of the upper body on the bicycle. The only possible advice that we can give here is to find out through trial and error. At this point, we should make a few remarks about saddle tilt, i.e., whether the saddle should be placed in a horizontal position or not. In principle the saddle should be placed horizontally. In case of a "positive saddle tilt" (i.e., saddle pointing upwards), the cyclist runs the risk of numbing certain parts of his body. As a consequence, the cyclist will be inclined to tilt his pelvis backwards which results in more pressure on the lower back. If the saddle is pointed downwards ("negative saddle tilt"), the cyclist will tend to slide forward. This is very uncomfortable not only because the narrower front part of the saddle gives too little support, but also because the arms, wrists and hands are subjected to too much pressure as a result of the cyclist trying to maintain a normal position on the saddle. The height of the saddle plays an important role in experiencing the bicycle as comfortable. If the saddle is placed too high, the cyclist runs the risk of overstretching his muscles; if the saddle is placed too low, however, the pressure on his quadriceps might become disproportionately high. Also see the chapter on efficiency: height of the saddle.

The handlebars

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Research has been conducted into the relationship between the adjustment of the handlebars and a comfortable position on the bicycle (Bremmer 1994). The most important conclusion of this survey is that the distance between saddle and handlebars is very much a matter of personal preference. The disadvantage of this kind of practical research is that the element of habituation can have a substantial effect on the measuring results. The experience of bikefitting.com is that a cyclist does not experience an adjustment of distance and difference in height between saddle and handlebars as comfortable when the advice on this matter deviates from what the cyclist is used to. Our experience, however, also shows that eventually the majority of cyclists believes the new adjustment to be an improvement. The handlebar-width should correspond with the width of the shoulders. Handlebars that are too wide automatically increase the frontal surface area of the cyclist and lead to loss of aerodynamic advantage. An additional drawback is that the cyclist will also show a sagging between the shoulder blades. In the long run, this will lead to complaints of the neck and shoulders. Contrary to common belief, handlebars that are too narrow will not result in loss of oxygen intake; however, narrow handlebars often lead to more nervous steering than wide handlebars and, hence, to loss of comfort. The steering angle should be adjusted in such a manner that the lower arm and hand are positioned in one line, as much as possible. It is clear that a correct aerodynamic position and a comfortable position of the torso do not always go hand in hand. Depending on the discipline the cyclist is engaged in and the speed he develops, he will decide on his position accordingly.

The pedals.

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Together with the cycling shoes the pedals form a unity through which the cyclist transfers movement to the bicycle. For matters of comfort it is important that shoes and pedals offer sufficient stability, enabling the movement of the knee to remain in line-of-force with the hip and foot. Contrary to popular belief, the cyclist has to adjust himself to the movement imposed on him by the bicycle. This implies that the link shoe-pedal (shoe cleats) is subordinated to this imposed movement. The position of the shoe cleat ensures that the foot is positioned straight on the pedal, so as to give stability to the knee joint. This explains why the link shoe-pedal should be stable in itself. The pedal should also be sufficiently wide because the entire front part of the foot must be supported. In order to cut back on weight and to decrease air resistance, pedals are often made as small as possible. So small, in fact, that stability depends entirely on the rigidity of the shoe and shoe sole, and on the link with the pedal. In reality this stability leaves a lot to be desired. With respect to the adjustment of the shoe cleat and complaints as a result of instability of the front part of the foot, we refer you to the Shoe Cleat Adjuster and the FAQ.