| Summary: | The aim of this study was to evaluate the possible benefits of using a non-circular chain-wheel system Q-Ring (Q) versus a conventional one (NQ) on the performance in the Bicycle Moto Cross (BMX) sprint cycling discipline. Fourteen riders belonging to the Spanish National Team performed a sprint test (3.95 s of duration, randomized and counterbalanced), from the starting gate ramp in a BMX track. The T-Test contrast analysis for related samples showed no statistically significant differences for the variables Average Speed (Vmean) and Time in 31m (T31m) between Q and NQ, when considering the group as a whole. However, when the analysis considered two groups separately: Experts vs Novice, we found significant differences for Q vs NQ within the Experts (Vmean: 5.91±0.03 vs.5.81±0.05 m/s; T31m: 3.21±0.02 vs 3.23 ± 0.02 s; P <0.05); what meant an improvement up to 40 cm in the distance covered within this first 3.95 seconds. Hence, our results suggest that the non-circular chain-wheel system Q-Ring improves sprint performance in BMX, provided the riders have a conditional level enough to ensure the capacity to develop the pedaling properly, despite of the strength needed.
Key Words: Mechanical efficiency, non-circular, pedaling, performance, sprint, BMX
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