The effect of the rotor crank system on time-trial cycling performance

The Rotor (ROT) is a cycle crank configuration that allows the pedals to move independently in an attempt to eliminate the “dead spots”, where torque output is minimal. Delta efficiency has been found to be significantly improved during an incremental test when using ROT in a group of untrained cyclists (Santalla et al., 2002: Medicine and Science in Sports and Exercise, 34, 1854-1858). However, no study has investigated whether ROT affects cycling performance directly. Therefore, the purpose of this study was to investigate the effect of ROT on time-trial cycling performance.

Following institutional ethics approval, 12 competitive male cyclists (Age mean 34.6, s = 7.1 years, Mass mean 75.9, s = 7.8 kg, max mean 4.5, s = 0.3 L•min-1, Wmax mean 363, s = 37.7 W) provided written informed consent to participate. All subjects completed two 40.23-km time-trials on a Kingcycle ergometer in each of two conditions, i) using conventional bicycle cranks (CON) and ii) using the Rotor system (ROT). Cyclists trained for 6-weeks prior to the experimental trials as either habitual ROT users or habitual CON users. Power output, speed, heart rate, , RER and gross efficiency were measured for the duration of each time-trial.

A two-way repeated measures ANOVA (pedalling system used during the test [CON, ROT] x habitual pedalling system [CON, ROT]) was performed to determine if there was a significant condition effect on the following variables: power output, speed, heart rate, , RER and gross efficiency. Statistical significance was set at P < 0.05 for all tests. Power output was not different between conditions (CON mean 255, s = 44 W vs. ROT mean 253, s = 40 W; P > 0.05). Indeed, no effect due to the pedalling system used during tests was found for any of the measured variables (P > 0.05). Furthermore, there was no interaction effect between the two factors for any of the measured variables (P > 0.05). However, there were marked differences between conditions for some individuals. For example, power output was ~11% higher during the CON trial vs. the ROT trial for one subject but ~12% lower in another.

These results suggest that the Rotor crank system does not impact on time-trial cycling performance. However, marked differences were observed between CON and ROT in some individuals, suggesting that ROT may be beneficial in some instances.