Efficiency of trained cyclists using circular and noncircular chainrings

The purpose of this study was to determine oxygen consumption (VO2), heart rate (HR) response, and rating of perceived exertion (RPE) of trained cyclists using noncircular and circular chainrings over a range of gears and pedal cadences. The subjects included 7 male cyclists (6 USCF licensed riders, 1 national qualifying triathlete). Each subject rode his own bicycle mounted on a wind-trainer at gears of 5.92 and 7.33 meters with noncircular and circular chainrings at pedal cadences of 50, 70, and 90 rpm. VO2, HR, RPE, and respiratory exchange ratio (RER) measurements were made during each of the 12 rides. Mean percent VO2max for each condition ranged from 28.7 +/- 2.1% with the 5.92 meter gear at 50 rpm to 83.4 +/- 4.3% using the 7.33 meter gear at 90 rpm. The results indicate no significant difference in any of the parameters measured between the two chainrings for any of the experimental conditions. The data indicate that the noncircular chainrings used in this study were not more efficient than the standard circular chainring for trained cyclists.