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PHYSIO BIKE FIT SERIES (PART 3) CAN YOU RIDE FASTER WITH LESS EFFORT?

PHYSIO BIKE FIT SERIES (PART 3) CAN YOU RIDE FASTER WITH LESS EFFORT?

Often the forgotten aspect of cycling is an effective (mechanical) and efficient (physiological) pedalling technique. Optimising your pedalling is fundamental to going faster on the bike. First, get the ‘engine’ right and then you can fiddle with aerodynamics.

Pedalling technique is often a contentious issue with no definitive long-term study on athletes adapting to a particular pedalling style (Wainright, 2018). However, physics and biomechanics can guide an optimal technique that you should aim for.

Mechanical Effectiveness

The diagram (figure 1) shows us how forces on the pedal are converted into propulsion at the crank. Looking at the pure physics of a pedal cycle, it seems optimal to maximise tangential forces around the ‘clock face’ of the pedal cycle.

Figure 1. The small arrows show the tangential forces around the pedal cycle (Kento Yamashita et al, 2013).

 

 

 

 

 

 

 

 

This effectiveness or in other words, mechanical ideal, would suggest that a circling or pulling-up technique would be optimal for cycling (Korf et al, 2007). Consequently, the phrase ‘pedal in circles’ is often used in cycling. However, the human body’s physiology and the distribution of our muscles also have to be considered.

Physiological Efficiency

Efficiency not only looks at propulsion but also your body’s energy expenditure.  Pushing down is often a rider-preferred pedalling style and often has the lowest physiological cost, but also the lowest mechanical effectiveness (Korf et al, 2007). The opposite is true for ‘pulling’ up or ‘circling’. These types of pedalling use more energy, but are also more mechanically effective at producing propulsion as they utilise stored energy in the cycle. The increased energy expenditure likely stems from pulling up being against gravity, but also, the human body not being designed well to ‘pull up’. i.e., using your calves and hamstrings more to pull up is less efficient compared to using more of your larger glutes and quads to push down. This is why at times of increased power and/or increased fatigue, the cyclist’s glutes and quads (larger muscles of the bottom and thigh) work proportionally more.

To summarize: pushing down is the easiest but least effective. Circling is the hardest, but most effective.

Therefore, a balance needs to be found and trained.

The ideal balance

Elite cyclists are better able to align to the theoretical ideal, but not fully. On average they do tend to exhibit more of a pulling action in the 3rd and 4th quarters (figure 2) (Garcia Lopez et al 2016). Interestingly, they don’t have their muscles contracting the whole time. Rather, they have noticeable gaps in muscle activation. This means they use a pattern of activation and then rest with each cycle. On the other hand, novices and triathletes tend to have their muscles working the whole time (Chapman et al, 2008). Therefore, it would appear that the training of high-level cyclists enables them to use both strategies, push down powerfully, and pull back, but then also recover to enable another powerful push-down phase. This becomes more and more efficient over time and is quite different to pedalling a full circle.

Figure 2. The 4 quarters of the pedal cycle. Elite cyclist are better able to align their pedalling force with the mechanical ideal and therefore, exhibit a bit more of a pulling action in the 3rd and 4th quarters (Garcia Lopez et al, 2008, Image taken from Dr Bini lecture)

 

 

 

 

 

 

 

 

 

 

Practical Implications

Rather than pulling up or trying to pedal a perfect circle, the best balance would be to ‘pedal in semi-circles.’ That would be to pull back on the pedal from halfway through the down stroke, around the bottom and then, relax mildly over the top half, before re-applying power. Rather than actively pulling ‘up’, a useful cue is, “Scrape mud off the toe of your shoe”. This action of pulling backward creates a reaction force that ‘flicks’ the pedal over the top half of the stroke. It is important to relax mildly during this top half of the cycle, as this is the energy storing and relative recovery phase. During this time, the muscles ‘store energy’ in their elastic component, before being reapplied again on the down stroke (Blake 2012). What you end up with is two alternating semi-circles driving the bike forward. (Check out the video I did to explain)

 

 

 

 

 

Figure 3. In contrast to the first diagram (figure 1), this image aims to depict how an elite cyclist would pedal. The relative different arrow sizes, help to illustrate which parts of the pedalling cycle should be emphasised to move closer to an ideal balance between mechanical effectiveness and trained physiological efficiency.

 

 

 

 

 

 

 

 

 

 

 

Conclusion

Overall, just like a technique for swimming and running, pedalling technique can be trained and improved. This can lead to huge increases in performance. Barney Wainwright, a sports scientist who extensively researches this particular subject is always testing the mechanical efficiency of elite cyclists. He says, “They [elite cyclists] could have 20-40 watts more by changing their pedalling style and getting better mechanical efficiency.” While this anecdote strays a bit from the analytical focus of this article, it does help to highlight the importance of not neglecting how you pedal and emphasises that with practice it should be possible to ride faster with less effort!

Kieran Storch

Physiotherapist

 

Physio Kieran is also a professional triathlete, most recently winning Mooloolaba Tri this year. He is passionate about getting Bike Fits right for performance as well as injury prevention. To chat through your issues as well as specific goals, message him at [email protected] to discuss a plan that is right for you.

 

To book an appointment call us at 07 3847 8040

For more information check us out at blphysio.com.au

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