Effects of a non circular chainring on muscular, mechanical and physiological parameters during cycle ergometer tests

This study analysed muscular, mechanical and physiological parameters using a circular chainring (CC) and a non circular Osymetric chainring (OC). OC was characterized by the use of a lower radius during top and bottom dead center and a higher radius during downstroke and upstroke phases. Twelve triathletes performed (i) an 8 min submaximal test and (ii) two 8 s maximal sprint tests. Gross efficiency was calculated during the submaximal test. Instantaneous external force and pedalling rate were recorded and the instantaneous net crank torque was calculated during both tests. Lower limb muscles coordination pattern (timing and magnitude) were also recorded. During the submaximal test, the only significant differences were the lower net crank torque of OC vs. CC at 0 degrees and 180 degrees and the higher net crank torque of OC vs. CC at 900 (P < 0.05). Concerning the sprint test, the only significant difference was the higher burst duration of the biceps femoris muscle with OC (P < 0.05). Present results indicate that OC facilitated mechanically the foot path at 0 degrees and 180 degrees. Nevertheless, this mechanical effect did not seem to be sufficient to improve performance since the muscles coordination pattern was not modified.