Enhancing cycling performance using an eccentric chainring

Purpose and Methods: This study was designed to compare the physiological r esponses and performance of well trained cyclists riding with two different chainring designs, round or eccentric, during a brief and intense cycling exercise: an "all-out" 1-km laboratory test. The eccentrically designed cha inring was made of two crank arms sliding into each other, with the inside arm fixed on the center of the arm of a circular chainring and the outside arm sliding along the inside and revolving around an elliptical cam. This d esign increases crank arm length at the downstroke and decreases it during the upstroke, thus increasing and decreasing the torque. In terms of the ch ainring's revolution, the crank rum length at 0 degrees and 180 degrees is similar to the arm length of circular chainrings (175 mm). However, during the downstroke (0-180 degrees), it increases to its maximum length of 200 m m at 90 degrees and then returns to its original length of 175 mm at 180 de grees. During the upstroke, it decreases to a minimum length of 150 mm at 2 70 degrees and then increases to 175 mm at 360 degrees. Eleven cyclists per formed an all-out 1-km laboratory test using each chainring. The study was conducted over two consecutive weeks with the order of chainring use random ized. During all trials, ventilatory data were collected every minute using an automated breath-by-breath system. Heart rate was measured using a tele metry system. Results: None of the cardiorespiratory variables showed signi ficant differences between chainring trials. Performance, however, was sign ificantly improved using the eccentric design (64.25 +/- 1.05 vs 69.08 +/- 1.38 s, P < 0.004, with the eccentric and the round design, respectively). Conclusion: We concluded that the eccentric chainring significantly improve d the cycling performance during an all-out 1-km test Further testing with indoor cycling specialists performing on a velodrome would be helpful to de fine the maximal possibilities of such a chainring.