Efficiency and pedalling technique: pulling or pushing?
Like in all endurance sports, efficiency is key during cycling competitions. The theory is simple: the less energy you use during the major part of the race, the more energy you will have available during the last sprint or climb. Or you are just able to go further and longer at the same intensity during your training rides.
Efficiency is defined as the ratio between the work that is performed to the energy that is expended. In other words: when your efficiency is 100%, all the energy you spend will be used to produce (external) work. This of course isn’t realistic. For example, a lot of energy will dissipate as heat. Therefore, efficiency won’t be even close to 100%, or 50% whatsoever.
Pedalling technique and efficiency
Instead, efficiency will be near 20%! Nevertheless, small or marginal gains might be the difference between coming in first or second. Since gains in efficiency may potentially be very beneficial for performance, people are looking for ways to improve it. One of the things that might affect this cycling efficiency, is the pedalling technique.
In this case, pedalling technique is related to the way that forces are produced and transferred to the pedals. Often an even distribution of torque throughout the crank cycle is said to be an efficient technique according to coaches. Ideally, the most effective force or torque application will cost the least energy. But is that really the case? How do mechanical effectiveness and metabolic effectiveness (efficiency) interact in different pedalling techniques? Thomas Korff and his research group tried to answer this question.
First, we need to define some of the concepts:
- Energy expenditure is (in this case) calculated using oxygen consumption of and carbon dioxide production by the body. These values are measured using breath-by-breath gas analysis.
- Efficiency, or Gross Efficiency, was calculated by dividing power output by the energy expenditure.
- Effective Force is the force exerted on the pedals that’s in the same direction of the movement.
- Resultant Force, the total force that is exerted on the pedals. These may for example also include shear forces between the pedal and foot and therefore won’t be the same as the effective force.
- Index of Force Effectiveness is the ratio between the Effective Force and the Resultant Force. In other words: this is the percentage of the total force that’s in the same direction as the movement. The higher the percentage, the higher your mechanical effectiveness, since you will “waste” less of your force production.
- Evenness of the torque distribution was calculated as the mean torque of a crank cycle, by the maximum torque. The higher this percentage, the higher the evenness of torque production during the crank cycle.
To be able to demonstrate the differences between pedalling techniques, cyclists were asked to adopt different pedalling techniques at a non-fatiguing intensity:
- Preferred technique
- Circling technique; focus on the transition through top dead centre and bottom dead centre
- Pulling technique; focus on an active pull during the upstroke of the crank cycle
- Pushing technique; focus on an active push during the downstroke of the crank cycle
Evenness of torque distribution
The evenness of the torque distribution was highest when adopting the pulling pedalling technique, and lowest when adopting the pushing pedalling technique. This makes sense, since actively pulling produces torque during the upstroke, which decreases the difference between torque production during the up- and downstroke. In the other pedalling techniques, a considerable amount of negative work was produced during the upstroke of the crank cycle. And as the word already suggests, negative work isn’t desirable.
So, adopting a pulling pedalling technique results in a more evenly torque distribution. But what is the effect of the pedalling technique on the force effectiveness? The results of the study show us that the force effectiveness was greater in the pulling technique compared to the other techniques. This means that a greater amount of the exerted force on the pedals was in the right direction in the pulling technique. This also makes sense, since you will exert (extra) force upwards during the upstroke, compared to the other pedalling techniques!
It seems that the pulling technique scores best in the tests so far. You’ll direct your force better and you’ll distribute your torque production more evenly across the pedal stroke. The latter is sometimes referred to as an efficient pedalling technique. However, in contrast to that believe, the results of the current study show a deterioration of the gross efficiency when adopting a pulling pedalling technique!
The gross efficiency in the other techniques was quite similar but were all significantly better than that in the pulling technique. Because the gross efficiency doesn’t seem to differ very much between the other pedalling techniques (pushing, preferred and circling), it may be speculated that pedalling technique is not that important in steady-state cycling performance. Except when adopting a pulling technique…
Does this mean that pulling is bad all the time? No, of course not! This study was performed during steady-state cycling. This means that during your local group ride or main parts of a race, you’ll probably want to avoid pulling the pedals too much. However, during an attack or an all-out sprint, this may not be the case! Also, gross efficiency may be improved with ‘learning’. The new ‘technique’ may be less efficient at first, but you might learn to become more efficient by training pedalling technique. Perhaps even when adopting a pulling pedalling technique!
Mechanically speaking, the pulling technique is most effective, but metabolically less efficient. This may suggest that the leg extensor muscles used during the downstroke of the crank cycle are metabolically more efficient than the leg flexor muscles that are used during the upstroke.
Encouraging riders to evenly distribute torque during the crank cycle may therefore be counterproductive, since you encourage them to pull more actively. This seems to decrease the efficiency of the movement. In addition, gross efficiency didn’t differ much between the other three (push, pull and preferred) conditions.
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