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.
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.
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.
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