• Corpus ID: 30130665

Why do appropriate non-circular chainrings yield more crank power compared to conventional circular systems during isokinetic pedaling ?

@inproceedings{Malfait2017WhyDA,
  title={Why do appropriate non-circular chainrings yield more crank power compared to conventional circular systems during isokinetic pedaling ?},
  author={L. Malfait},
  year={2017}
}
Several studies have been published on the use of eccentric and non-circular chainrings. The findings of these studies have, however, not been consistent. Despite the lack of consistent positive results in terms of physiological responses, a consensus appears to prevail that the improved mechanical effectiveness of the oval chainring may lead to performance enhancement (e.g. increased crank power output) compared to the conventional circular chainwheel. Some authors assume non-circular… 
Effects of a Non-Circular Chainring on Sprint Performance During a Cycle Ergometer Test.
TLDR
The Osymetric non-circular chainring significantly maximized crank power by 4.3% during sprint cycling, in comparison with a circular chainring, mainly explained by a significantly higher instantaneous external force that occurs during the downstroke.
Non-circular chainring improves aerobic cycling performance in non-cyclists
TLDR
Results showed a higher maximal aerobic power attained with the non-circular chainring, obtained only for non-cyclists, which allowed highlighting the link between cycling equipment modifying the pedalling motion and physiological responses.

References

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TLDR
The chainring shape that maximized average crank power balanced these competing demands by providing enough eccentricity to increase the external work generated by muscles during the power phase while minimizing negative work during the subsequent recovery phase.
Physiological response to incremental stationary cycling using conventional, circular and variable-geared, elliptical Q-chain rings.
TLDR
Despite the popularity of non-circular chain rings and the apparent mechanical advantage derived from their use, the findings of this study were unable to provide support for significant physiological advantages when using Rotor Q-rings with an eccentricity ratio of 1.10 and 74° default setting.
Effect of chain wheel shape on crank torque, freely chosen pedal rate, and physiological responses during submaximal cycling.
TLDR
A musculoskeletal simulation model supported the idea that a contributing factor to the observed difference in blood lactate concentration may be slightly reduced muscle activity around the phase where peak crank torque occurs during cycling with the Biopace chain wheel.
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TLDR
The gross efficiency of cycling was not improved by any of the noncircular chainrings, and for cycling events where efficiency is a determinant of performance, the non Circular chainring do not offer any advantage over round chainrings.
Effects of a non circular chainring on muscular, mechanical and physiological parameters during cycle ergometer tests
TLDR
Present results indicate that OC facilitated mechanically the foot path at 0° and 1800 Nevertheless, this mechanical effect did nOI seem to be sufficient to improve performance since the muscles coordination pattern was not modified.
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TLDR
It is concluded that the eccentric chainring significantly improved the cycling performance during an all-out 1-km test and further testing with indoor cycling specialists performing on a velodrome would be helpful to define the maximal possibilities of such a chainring.
The use of an eccentric chainring during an outdoor 1 km all-out cycling test.
TLDR
It is suggested that the subjects who had greater lower limb muscle volume and greater calf muscle volume, seem to have had a significant advantage in performing with the eccentric chainring, and the maximal possibilities of this chainring should be defined.
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TLDR
During nonisokinetic sprint cycling, the decrease in power output when pedaling rates increased beyond PRopt may be partly explained by suboptimal muscle coordination.
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TLDR
Comparison of the physiological response in this study did not translate into an advantage of the Harmonic over circular chainring during submaximal and maximal pedaling in trained cyclists.
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TLDR
It is suggested that power liberated in the joints should be judged as the source of power in the power equation and should be defined as external power in this and other human movement.
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