Noncircular Chainrings Do Not Influence Maximum Cycling Power

Noncircular chainrings could increase cycling power by prolonging the powerful leg extension/flexion phases, and curtailing the low-power transition phases. We compared maximal cycling power-pedaling rate relationships, and joint-specific kinematics and powers across 3 chainring eccentricities (CON = 1.0; LOW_ecc = 1.13; HIGH_ecc = 1.24). Part I: Thirteen cyclists performed maximal inertial-load cycling under 3 chainring conditions. Maximum cycling power and optimal pedaling rate were determined. Part II: Ten cyclists performed maximal isokinetic cycling (120 rpm) under the same 3 chainring conditions. Pedal and joint-specific powers were determined using pedal forces and limb kinematics. Neither maximal cycling power nor optimal pedaling rate differed across chainring conditions (all p > .05). Peak ankle angular velocity for HIGH_ecc was less than CON (p < .05), while knee and hip angular velocities were unaffected. Self-selected ankle joint-center trajectory was more eccentric than HIGH_ecc with an opposite orientation that increased velocity during extension/flexion and reduced velocity during transitions. Joint-specific powers did not differ across chainring conditions, with a small increase in power absorbed during ankle dorsiflexion with HIGH_ecc. Multiple degrees of freedom in the leg, crank, and pedal system allowed cyclists to manipulate ankle angular velocity to maintain their preferred knee and hip actions, suggesting maximizing extension/flexion and minimizing transition phases may be counterproductive for maximal power.