Pedalling Technique and the Wattbike
by Henry Peacock
For most of us, the last time we were taught to ride a bike was in childhood, and once we were able to ride safely that was that. Elite cyclists and triathletes have a very different experience - they have a coach who not only assigns their training, but also coaches technique.
Coaches often talk about pedalling in circles and scraping mud off the soles of your shoes (to maintain momentum at the bottom of the pedal turn), but for the first time with the Wattbike, it is possible to show how force is delivered in the pedalling action, and improve technique where necessary.
The Wattbike has a unique force curve view on the monitor and software, which allows you to have a visual display of how you are applying force in the pedal turn. If the pedals were being turned by a motor - the optimal shape for the force curve would be a circle, with even distribution of force applied at all points in the pedal turn, but the human body is not designed like that.
As bipeds we are designed with large muscles at the front and back of our legs which allow, with the aid of gravity as we lean forward, walking and running. They are very powerful when straightening the leg (as in standing from a squat position, or pushing down on the pedal), but are less effective when drawing the pedal back at the bottom of the pedal turn. As a result trying to elicit the same force at the bottom of the pedal turn as during the down stroke would be an ineffective use of the body's natural strength.
We have extensive data from elite cyclists (road and track) and triathletes which confirms this, and from this data we have been able suggest an optimum shape for the force curve.
'Pedalling in circles' is a phrase often heard - quite obviously the pedals do turn in a circle but that's not the same as applying the force in a circle or using the correct leg muscles to produce both forward momentum and leg speed.
The Cycling Muscles
Cycling power is mainly delivered by the extension muscle group (quadriceps and gluteals). The quadriceps extend the knee and the gluteals extend the hip. The flexion muscle group (hamstrings, psoas and gastrocnemius/soleus) unload and recover the leg preparing the leg for the next leg extension.
There is minimal force contribution (force that propels a bike forward) on the upstroke or flexion phase of the cycling stroke. Any contributing force on the upstroke is countered by the positive force contribution of the downstroke power phase (extension) of the other leg. Improving the weaker upstroke beyond an optimum level may not be good use of available power.
The flexion muscle group is weaker than the extension group. Emphasizing the weaker muscle group by working on the upstroke will not necessarily lead to increased power for propelling a bike forward.
The application of the upstroke and therefore the use of the flexion muscle group needs to be sufficient to continue pedal momentum and reduce the effects of any 'dead spots' at the top and bottom of each leg action without compromising the delivery of force that propels the bike forward.
The Wattbike Force Curve - What does it show?
The Wattbike force curve creates a force profile for each and every pedal revolution. Not only can you see the force curve in real time but the Wattbike Expert software the data for every revolution can be stored for further analysis.
For the downstroke of each leg the Wattbike force curve tracks the angle of peak force, the percentage contribution (balance of each leg) and maps the force curve so that the overall 'shape' can be viewed visually (the back up sampling data is available in the software).
The force curve on a Wattbike shows the force profile of the left and right leg downstroke:
Three Phases of Development of Good Pedalling Technique
The Figure Of Eight
The figure of eight typifies a beginner, or even a more experienced cyclist who has never been coached. The rider loses pedal momentum on the transition from right-leg to left-leg (point 1) and left-leg to right-leg (point 2).This has the effect of accelerating the bike during the left and right leg down stroke, but allowing the bike to slow down again during the transition between legs.
This means that the rider must produce more power to achieve the same speed as a rider who pedals more effectively.
The Peanut typifies a good cyclist, or someone who naturally understands how to deliver force to the pedals to good effect - people who ride fixed crank bikes naturally have a better understanding of maintaining pedal momentum and often show the peanut shape.
This cyclist maintains some pedal momentum between leg drives. However, there is still a noticeable loss of momentum - especially since (in this case) at point 2 there is a larger dead spot than at point 1. Although better than the figure of eight, this rider is still wasting some of their power with ineffective transition between left and right legs.
This is the shape we have seen from elite cyclists and triathletes, no matter what their discipline, track, road, mountain, time-trial or triathlon. The shape demonstrates a strong down stroke with a good draw to maintain the pedal momentum throughout the transition between legs.
This cyclist has a large shape, which is consistent, balanced between each leg and maintaining good pedal momentum throughout.
What about the angle of peak force?
This depends on the cycling activity, the ability of the cyclist, using high/low resistance (high low gears), high/low cadence, whether in the saddle or out of the saddle and overall cycling position.
The angle of peak force can be anywhere within the 90Âº to 180Âº quadrant although when at optimum cadence and gearing the angle of peak force is in a very narrow range (the examples indicate which force curves we believe to have an overall effective shape, balance and angle of peak force).
In general, relative to the ability of the cyclist a high resistance will narrow the angle whilst low resistance will create a steeper angle. Cadence also moves the angle with high cadence again, in general making the angle steeper (gravity and pedal momentum).
What we have found to be consistent in top cyclists is the ability to maintain a 'sausage' force curve shape irrespective of the angle of peak force (and with good balance and equal angle of peak for in each leg).
Some examples to demonstrate the effects:
Top riders all tend to display the 'sausage' with good balance and an equal angle of peak force on each leg.
World class sprinter (high resistance/high cadence 1488 W 144 rpm)
Triathlete (medium resistance/medium cadence 265 W 95 rpm)
Tour rider (Low resistance/high cadence 460 W 135 rpm)
Tour rider - In the saddle/out of the saddle (high resistance/medium cadence 350 W 90 rpm)
Why is good pedalling technique important?
Our research indicates that cyclists/triathletes who have refined their pedalling technique report the ability to produce more power with the same physiological effort. Triathletes report a faster bike leg and as a consequence of more effective pedalling technique and physiological effort, a faster run leg.
What are the implications for training?
For the first time it is possible to see, in real time how effectively the cyclist is pedalling.
Using the Wattbike, cyclists can refine their pedalling technique to get the best result, tracking the force curve, cadence, power output, HR and a host of other cycling parameters (the Wattbike measures 39 different cycling parameters) all in real time with great accuracy (+/- 2% across its whole range).
Riding on the Wattbike you can quickly see how changing your cadence, gearing and body position effects your ability to deliver the correct force curve shape.
Producing the most effective force curve is dependent not only on pedalling technique, but also selecting the correct cadence and resistance level on the Wattbike or cadence and gearing on your bike. Using the Wattbike it is possible to test at different cadence and resistance levels to find out which combination delivers the optimum power and physiological response.
A harder gear (increased resistance on the Wattbike) beyond the capability of the rider will reduce the angle of peak force, but will also make it harder to maintain pedal momentum in the transfer between legs - meaning that it will be more difficult to maintain the correct shape, cadence level and physiological response.
Reducing the gearing (resistance on the Wattbike) will increase the angle of peak force, allow a higher cadence and can be used to improve the shape with low physiological effort. Using Wattbike Expert software it is also possible to monitor if the angle of peak force is the same on both legs and if not, the rider can use the live real time force curve to improve balance and equalize the angles.
Using the Wattbike, physiological and pedalling technique improvements can be monitored in real time and tracked over training cycles. This means that every session can be precisely tailored to the requirements of the individual, allowing huge performance gains to be made in a very short space of time.
To read more on the Wattbike visit the website at www.wattbike.com. There is an extensive Training Guide on the website www.wattbike.com/trainingguide which includes cycling tests and specimen Training Plans that can be followed by all cyclists/triathletes.
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