Noncircular Chainrings Do Not Influence Physiological Responses During Submaximal Cycling

Area of Science:

• Sports Science
• Biomechanics
• Exercise Physiology

Background:

• Metabolic cost in submaximal cycling is primarily driven by pedal speed and power output.
• Noncircular chainrings can modify crank angular velocity, potentially affecting pedal speed.
• Altering pedal speed during high-power phases could theoretically reduce metabolic cost and improve efficiency.

Purpose of the Study:

• To isolate the effects of pedal speed and chainring shape on metabolic cost.
• To evaluate how chainring eccentricity influences joint kinematics and kinetics during cycling.
• To compare three chainring eccentricities (CON, LOW, HIGH) at various intensities and cadences.

Main Methods:

• Eight cyclists completed submaximal cycling tests at 30%, 60%, and 90% of their lactate threshold.
• Tests were conducted with standard (CON) and noncircular (LOW, HIGH) chainrings at 80 rpm.
• Additional tests used a CON chainring to match the pedal speeds of the noncircular conditions.
• Metabolic cost and gross efficiency were measured via indirect calorimetry.
• Joint-specific kinematics and kinetics were analyzed using pedal forces and motion capture.

Main Results:

• Chainring eccentricity and pedal speed did not significantly impact physiological or metabolic measures.
• The HIGH eccentricity condition reduced angular velocities in the knee and hip compared to the CON condition.
• Angular velocity during ankle plantar flexion was unaffected by chainring type.
• No significant differences in metabolic cost or gross efficiency were observed across conditions.

Conclusions:

• Noncircular chainrings alter joint angular kinematics but do not reduce metabolic cost or enhance gross efficiency in submaximal cycling.
• The studied noncircular chainrings do not offer performance benefits for trained cyclists.
• These chainrings neither improve nor compromise submaximal cycling performance.