The Relationship between Pedal Force and Crank Angular Velocity in Sprint Cycling

Area of Science:

• Biomechanics
• Human Physiology
• Sports Science

Background:

• The force-velocity relationship describes how muscle force production is influenced by contraction speed.
• In cycling, pedal force and crank angular velocity typically show a linear relationship, deviating from the hyperbolic intrinsic muscle force-velocity curve.

Purpose of the Study:

• To investigate why the relationship between tangential pedal force and crank angular velocity in sprint cycling is linear, rather than hyperbolic.
• To elucidate the underlying mechanisms causing this deviation from intrinsic muscle force-velocity properties.

Main Methods:

• Simulated isokinetic sprint cycling using a forward dynamic model of the human musculoskeletal system.
• Lower extremity muscles were modeled, and stimulation was optimized to maximize average power output across a range of crank angular velocities (30–150 rpm).

Main Results:

• Peak tangential pedal force decreased more with increasing crank angular velocity than predicted by intrinsic muscle properties alone.
• This linearizing effect was attributed to active state dynamics, specifically the timing of muscle activation and deactivation.
• Optimizing power output requires muscles to transition from high to low active states, necessitating early deactivation initiation as velocity increases.

Conclusions:

• The observed linear relationship between pedal force and crank angular velocity in sprint cycling is influenced by both intrinsic muscle force-velocity characteristics and activation dynamics.
• Understanding these activation dynamics is crucial for accurately modeling and predicting sprint cycling performance.