Mechanical modifications to increased step frequency while running freely outside

Area of Science:

• Biomechanics
• Running Science
• Sports Medicine

Background:

• Laboratory studies show increased step frequency alters running mechanics, potentially reducing injury risk.
• These changes include decreased ground impacts and altered stiffness.
• This study investigates if these effects translate to free-running environments.

Purpose of the Study:

• To determine if runners exhibit similar mechanical changes when increasing step frequency in a natural, uncontrolled environment compared to laboratory settings.
• To assess the impact of increased step frequency on running mechanics outside controlled conditions.

Main Methods:

• Twenty runners (10 male, 10 female) participated, with 8 completing the protocol.
• Runners wore a motion tracking system (RunScribe®) to record step length, impact forces, and stiffness.
• Participants ran on flat and incline surfaces at preferred speeds, then at a +5% increased step frequency guided by a metronome.

Main Results:

• On flat surfaces, increased step frequency led to decreased contact time (-11.5%), increased speed (+13.8%), impact (+9.8%), and vertical stiffness (+13.6%).
• On incline surfaces, increased step frequency resulted in decreased contact time (-7.7%) and increased vertical stiffness (+14.6%).
• Notably, ground impact did not decrease on either surface with increased step frequency.

Conclusions:

• In a free-running environment, increasing step frequency leads to increased step length.
• This adaptation does not result in reduced ground impact, contrasting with findings from controlled laboratory studies.
• Running specialists' advice to increase step frequency for injury prevention may need re-evaluation in natural settings.