Jones, A. D.
Abstract:
Background: As variable-geared, elliptical Rotor Q-rings may improve pedal dynamics by reducing the effect of the "dead spot" in the pedaling action and altering the mechanical leverage, use of these chain rings is currently gaining popularity among competitive amateur and professional cyclists. There are, however, no randomized, controlled, published studies examining the physiological effect of using Rotor Q-rings vs. standard circular chain rings. In addition, no previous studies comparing circular and noncircular chain rings have included analysis of the markers of exercise induced muscle damage. Aim: This work was designed to compare physiological response to an incremental cycling protocol when using Rotor Q-rings (QR) with an eccentricity ratio of 1.10 and 74° default setting, to that obtained when normal, circular chain rings (NR) are used. Methods: Twelve trained amateur cyclists (age: 40.67 ± 7.53 years) performed two incremental tests to exhaustion on their own bicycles in a controlled laboratory environment. The subjects were randomized to QR and NR trials which took place seven days apart, within a cross-over design. The type of chain ring attached to the cycle (QR vs. NR) was blinded from the participant. After an eight-minute warm-up at 130 W, the power output was increased by 30 W on the minute. During each trial, heart rate, VE, V02 were measured continuously and RPE and blood lactate concentration were measured during the last 15 seconds of each workload. Ventilatory and blood lactate turn- points were determined from serial VE and blood lactate concentrations. Serum lactate dehydrogenase (LDH) concentration was measured before and immediately after each trial. A numerical pain rating scale was used to assess post exercise leg muscle and knee joint soreness 24hr post trial. Results: There was no statistically significant difference (p > 0.05) in mean peak power output (380 ± 29.0 W vs. 385 ± 31.8 W), mean power (194.9 ± 12.7 W vs. 197.2 ± 16.7 W), mean distance covered (9.02 ± 1.29 km vs. 8.89 ± 1.84 km) during the QR and NR trials, respectively. There were no statistically significant differences between trials in submaximal and maximal V02, VE or RPE, and ventilatory or lactate turnpoints (p > 0.05). Knee pain and leg muscle soreness as well as and increment in serum LDH levels did also not differ significantly following the two trials (p > 0.05). The difference in peak blood lactate concentrations (12.62 mmol. £"' ± 2.15 on QR vs. 13.84 mmol. £"' ± 1.68 on NR), however, reached borderline significance (p = 0.055). Conclusion: 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, during an incremental cycling test to exhaustion. While the borderline significance of the lower mean maximal blood lactate concentration following the Q-ring trial requires confirmation in a larger study, the possible roles of training, higher eccentricity ratios and different orientations of the crank to the chain ring in eliciting a physiological advantage, require further investigation.
