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Pedal Stroke Efficiency

The bicycle is an incredibly efficient machine, arguably the most efficient way for a person to move on land.  According to Bill Nye (The Science Guy) …

“There is no machine known that is more efficient than a human on a bicycle.  A bowl of oatmeal, 30 miles, you can’t come close to that.”

When it comes to biomechanical efficiency of pedaling, an elite cyclist has a peak gross efficiency around 25%, whereas a novice is around 20% (not a big difference), and most of that difference has to do with workload.  As watts go up, biomechanical efficiency goes up, so to achieve 25% efficiency requires an output of 300-400 watts.

There seems to be a misconception that there is some secret to pedaling efficiently on a bicycle.  High mechanical efficiency is an important trait of elite cyclists, but the reasons seem to lie more within the muscles than as a result of actual cycling mechanics.  The efficiency of elite cyclists is directly related to percentage of type I muscle fiber cross sectional area in the vastus lateralis (Faria, Parker & Faria, 2005).  Neuromuscular factors such as motor unit recruitment, synchronization, and rotation are thought to be important factors.  So the best way to improve efficiency on the bike may be to ride more frequently and improve neuromuscular adaptations and physiological adaptations at the muscular level gradually over time.

MCC Chart 1

Should you pull up on the pedals?

The short answer is no.  If you look at the force vector diagram, you see the largest vector around the 4 O’clock position and even during the upstroke there is a small downward force vector.  This again has more to do with how the human body is most efficient at producing force.  The gluteal muscles and the quadriceps muscles are very efficient at producing a downward force, but the upward force is most efficient if it is passive.  Instead of thinking about pulling upward on the pedals, thing of just unweighting most of your leg during the upstroke.  The only type of cyclist that needs to actively pull up on the pedals is a sprinter or track cyclist.  Also, pulling up on the pedals can cause problems like tight hip flexors, hamstring injury, and low back pain.

Middaugh Coaching Chart 2

Where should I apply force to the pedals?

Forward and down, but mostly down.  Instead of trying to rotate the cranks like a motor, try a stronger impulse during the downstroke so you have a higher spike in peak torque like the graph below.  If you aim for the most power at the 3 O’clock position, then the most power is actually delivered at the 4 O’clock position.  When distribution of power was observed through the phases of the pedal stroke, national level cyclists actually had a more unequal power distribution and less effective application of power during the downstroke compared to state level cyclists (Coyle et al., 1991).  The national level cyclists had a higher spike in power during the downstroke even at equal power levels, which is contrary to popular belief.  The National level cyclists had very little negative torque during the upstroke, which is an important for efficient cycling (they were unweighting the pedal but not pulling up).

MCC Chart 3

Are triathletes more like elite cyclists or more like novices?

When triathletes, cycling novices, and elite cyclists were compared for pedaling mechanics, triathletes were comparable to cycling novices in that there was more variation between individuals, more variation between pedal strokes, and more muscle co-contraction (Chapman, Vicenzio, Blanch, & Hodges, ).  That doesn’t actually mean all triathletes pedal like novice cyclist, but some clearly do.  Part of this may be due to an interference with the transfer of training with multi-discipline training, and part may have to do with cycling experience, cumulative and acute cycling training loads.

Take-Aways

For the past 15 years I have been teaching high performance indoor cycling classes on CompuTrainers and now the Wahoo KickRs.  Everyone has their own bike set up on the smart trainer, so most are comfortable with their bike fit, their shoes and pedals.  Occasionally I have forgotten my cycling shoes and had to do the workout with running shoes atop a road pedal.  Not fun, but it is amazing to me how little difference it makes in output.  Last week one of the cyclists forgot her shoes and wanted to bail on the class.  I said, no problem, let’s just put a flat pedal on your bike and you will be fine.  It was the hardest interval workout of the year, but guess what, she kept her threshold power at the same level and completed the workout without issue (other than a little frustration with me).  I’m not suggesting to switch to flat pedals because clearly a well built cycling shoe and pedal is more comfortable and better for applying power.

So stop being so obsessed with pedaling mechanics.  Ride your bike often, at a range of pedaling cadences, and try to ride year-round.  Focus more on building cycling fitness and endurance and less on skills and drills for pedaling mechanics.

 

References

Chapman, A., Vicenzio, B., Blanch, P., & Hodges, P. (2007).  Leg muscle recruitment during cycling is less developed in triathletes than cyclists despite matched cycling training loads, Exp Brain Res, 181(3), 503-518.

Coyle, E., Feltner, M., Kautz, S., Hamilton, M., Montain, S., Baylor, A., Abraham, L., & Petrek, G. (1991).  Physiological and biomechanical factors associated with elite endurance cycling performance.  Medicine and Science in Sports and Exercise, 23(1), 93-107.

Faria, E., Parker, D., & Faria, I. (2005).  The science of cycling:  Physiology and training—Part I.  Sports Medicine, 35(4), 285-312.

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