Noncircular Chainrings Do Not Influence Maximum Cycling Power – Leong, C. H., Elmer, S. J., & Martin, J. C. (2017).

Jed Williams Research Review

Previous research has been inconclusive into the benefits of noncircular chain rings with some showing benefits and some showing no change, possibly due to different conditions present when testing.

The researchers’ prediction was that noncircular chain rings would facilitate greater maximal force production and would alter optimal power pedalling rate. The logic behind the use of noncircular chain rings is that they can extend the leg extension phase while shortening the transition period between pedal strokes. Previous work using a modelling software has been carried to test the basis of the prediction.
During the experimentation, the participants were asked to complete a familiarisation process to learn unfamiliar cycling patterns presented by the noncircular chain rings. Participants were visually blinded to the conditions of test to remove ‘placebo’ effects, however some could sense differences in pedal stroke. The order of the trials was randomised and there was a 48-hour minimum period between visits to eliminate order bias. The participants only had 5 minutes of warm up time before commencing with the test. This is worth noting as it could skew later tests as participant may have further warmed up as the testing progressed.

The noncircular chain rings were positioned to maximise time spent in leg extension phase, this was found to be between 333°and 165° of the pedal stroke. This ensured the largest part of the chain ring was engaged at halfway through leg extension.

The study was split into to two parts to test both sides of the researchers’ prediction. The first study compared power pedalling relationships and joint specific kinematics and kinetics with different chain rings. The second study considered maximal force production under the different chain ring conditions.

Upon collecting the data, the researchers’ found that their prediction was not proved. There was no detectable change in power production or in the optimal power pedalling rate.

They found that noncircular chain rings did influence crank angular velocity throughout the pedal stroke. Any changes however are absorbed in ankling patterns as hip and knee velocity remains constant across all conditions.

Ankling patterns are exploited by the body to maintain constant velocity of knee and hip joint. The ankling patterns at play may mean that noncircular chainrings are counterproductive for maximal power production. This then poses the question would noncircular chainrings be better if they were positioned to enhance normal ankle velocities. While theoretically counterproductive it would be interesting to research the effects of the different positioning of the noncircular chain rings. What the researchers did find was that noncircular chain rings have no negative effects on maximal power production, so their use is not going to hamper riders who prefer them.

A limitation of this study is that cyclists were given little exposure to performing maximal cycling using noncircular chainrings. Further research into the effect of noncircular chain rings on riders who traditionally train with them could potentially yield different results.

This study only tested at maximal intensities, so it is worth noting that noncircular chain rings may have a different effect at submaximal intensities which would have to be further investigated.

Leong, C. H., Elmer, S. J., & Martin, J. C. (2017). Noncircular Chainrings Do Not Influence Maximum Cycling Power. Journal of Applied Biomechanics, 1-29.

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