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A smooth action


Improve your pedalling style. The Munich engineer and biomechanics expert Wolfgang Petze calls just about everything into question, ever published about "smooth action". We explain his method and show how you can use to it improve your technique.


Pedal in a smooth circular style and make sure that all the forces on the cranks are used for efficient propulsion: That is how the well known smooth pedalling action might be summarised. At each turn of the cranks, continuously push, drag and pull - that is how correct pedalling has been taught to date... And it is wrong, says Wolfgang Petzke. His theory is that it isn't neccessary to concentrate on getting as much force as possible as smoothly as possible onto the pedals, but on improving the action of the legs biomechanically and energetically.

Petzke isn't just saying that, he has studied the sporting cyclist's leg and pedalling action like no-one else. The mechanical engineer was always fascinated right from his student days by this bio/technical problem. In the meantime he has developed a testing technique, with which he can tell not only total pedalling power but the magnitude and direction of the forces working on the pedal. He has also programmed software which simulates realistically the complex orchestration of muscles, joints and levers in a cyclist's leg. Both these techniques together have been given the name Caloped, which has for some years been used in the medical profession, to help patients in rehabilitation relearn muscle coordination and motion. Wolfgang Petzke also offers racing cyclists individual tests, to improve pedalling technique or to eradicate chronic afflictions caused by bad load distribution.

Aim: to have the muscles working together rather than against each other

The revolutionary approach in Caloped is that the force applied to the crank is no longer the main point; it isn't important, Petzke says, whether the forces are acting in the correct direction, whether the foot is pulling, dragging or pushing. Pretzke rather takes the leg (including hip and ankle joints) as a system and examines how movement and finally propulsive energy results from muscle tension. The trick in his programme is that by using the data from an exactly measured leg and the forces measured on his test pedal, he finds the working balance between each joint (hip, knee, ankle). The software shows this as power at hip, knee and foot. Now he can see if the muscles are working in harmony or antagonism - whether single muscle groups are helping propulsion or even opposing it. It is important to eliminate from the equation, the influence which the leg has, just through its mass and speed during the pedalling action. Other experts agree that this is an improvement over previous methods. Thomas Jaitner - junior professor in motion and training science at Kaiserslauten Technical University says, "The system works very well. The advantage lies in being able to study the reasons causing the motion."

The idea of uniform pedalling power is wrong

The ramifications are far-reaching for the circular action concept: the pressure (force) felt at the foot is no reliable indication that the leg musculature is working efficiently, because the mass of the leg is also exerting pressure at the foot. So there must be another way to define optimum pedalling technique. Petzke recommends, "Bring muscle tension and motion in harmony. Don't try deliberately to exert pressure in a particular direction at the pedals." The bio mechanic remembers the example of three riders from the German national team. They had trained, as advised by their trainer a dragging motion to the rear, just after reaching the horizontal crank position. "The muscle group at the rear of the thigh then worked in antagonism to the not quite completed stretching movement of the knee, which actually worsened the efficiency by several percent." Instead of that, says Petzke, you should keep the movement of the leg in your mind's eye and go actively with this motion. "Energy transfer to the pedal follows on automatically from this action."

The difference between the two motional patterns can be proven using his computer and test technique. An example: For a 200Watt average power per leg, using the Petzke method, the knee stretching muscles generate 300Watt maximum and the hip stretching muscles 250Watts. If you try to get the same average power by uniform circular pedalling, these same muscle groups have to generate a maximum of up to 350Watts. So if you concentrate of the leg movement instead of the force, you relieve the joints and also ride more efficiently.

If you find some orthopedic aspects in this article, you are correct. Petzke says, "Using Caloped I have been able to correct wrong load distribution in cyclists, who had had for instance knee pain due to wrong coordination, or power loss due to unnecessary muscle tension." One case is Stefan Famulla, a hobby racer from Dillingen. For over two years he had had knee pain while cycling. Doctors diagnosed cartilage damage but couldn't really help. Following analysis on the Caloped system, he altered his technique and says, "Ever since I can cycle without pain for the first time. I recommend anybody with knee pain to use this method." Adapting his style was not a problem for Famulla, but he had to remind himself for a season, not to fall back into the old way of pedalling. On the positive side he says, "I notice a definite performance increase too."

Go with your body's movement

How can you learn the motion Petzke recommends? The Caloped developer says, "Go with your body's motion - as a runner does. He is not worrying how much power he is transmitting to the ground. If muscle tension and joint movement are in harmony, no effort will be wasted." As an example of an athlete, who is orientated to motion, Petzke cites Lance Armstrong and gives a tip: "When you pedal, don't think of the power but follow up and augment the natural movement of your body. In this way you will naturally increase your speed of motion - in other words your pedalling frequency (cadence). The ability to alter cadence is very different from rider to rider, says Petzke, "I tested a professional, who could not change his cadence, no matter how he tried. Other riders find it easy to influence the power in the individual movements."

Unsmooth action

Diagram 1. The diagram shows a pedalling action in which the knee (red) is doing too little of the whole work (green) and is antagonising the action.

ideal smooth action

Diagram 2. This diagram shows a very good action. knee (red) and hip (blue) contribute a similar proportion of the whole work (green) . In the rearward part of the cycle, the power is lower but all in the direction of movement, in other words, used for propulsion.

Introduction to smooth pedalling action



ideal pedalling action at 90 degrees
Correct stretching of the leg:
Hip stretchers and knee stretching groups shorten quickly and generate energy. Automatically a force is applied to the pedal, transferring this energy 1:1. The crank leads the foot in a circular motion and supports the motion through radially oriented forces. These cause no energy loss (neutral supporting forces). Don't let the movement of the cranks to the rear cause you to apply a dragging force in this direction. before the knee is quite stretched in the 5 o'clock position. Pulling back with the "wrong" muscles behind the knee joint, which is still straightening and stretching causes an energy loss at first (in the leg) but does not result in an energy gain at the crank. The power works as shown by the green arrow and is equal to the energy transfer to the crank. Although of a higher value, energy cost for the muscles and joint loads are lower!

ideal action at 210 degrees
Correct lifting of the leg:
First the knee benders shorten (M-Biceps Femoris, short head) then the hip benders (Iliacus/Psoas). Both generate energy when shortening according their voluntary tension. When the motion of the thigh and lower leg is felt, the muscles are activated at the right time - or the right joint position. Once again (as always) there is an automatic application of power to the crank, which transfers this energy 1:1. Don't get distracted by the application of power. Instead feel the motion of your body. Then the muscle activation will occur with the correct timing! The notional direction of motion for activating the correct muscle groups is in the direction of the green arrow.

Summary The hitherto common view of the smooth pedalling action seems to have been superseeded. The way to a smoother more efficient pedalling action is not the force you feel at the pedals, but the muscle activity felt in the motion of the leg. More info on this subject (in German) at www.caloped.de.

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