Duty factor and foot-strike pattern do not represent similar running pattern at the individual level

Area of Science:

• Biomechanics
• Sports Science
• Running Dynamics

Background:

• Runners are classified by duty factor (DF) and foot-strike pattern (FSP).
• DF is considered a more global measure than FSP, which is determined by foot-strike angle (FSA).
• The relationship between DF and FSP classification has not been previously studied.

Purpose of the Study:

• To investigate the relationship between foot-strike pattern (FSP) and duty factor (DF) in runners.
• To determine if runners classified by FSP align with those classified by DF.
• To assess the utility of DF versus FSP/FSA for evaluating global running patterns.

Main Methods:

• One hundred runners were analyzed while running at 9, 11, and 13 km/h.
• Force data (1000 Hz) and whole-body kinematics (200 Hz) were collected using an instrumented treadmill and optoelectronic system.
• Runners were classified based on their foot-strike angle (FSA) and duty factor (DF).

Main Results:

• Weak correlations were found between foot-strike angle (FSA) and duty factor (DF).
• The sensitivity between foot-strike pattern (FSP) and DF groups was 50%, indicating limited agreement.
• Only half of the runners were consistently classified into corresponding FSP and DF groups.

Conclusions:

• Foot-strike pattern (FSP/FSA) and duty factor (DF) provide distinct information about running patterns at the individual level.
• Duty factor (DF) is a more suitable metric than FSP/FSA for assessing the overall running pattern of an individual runner.
• DF offers a more global perspective on running mechanics compared to the localized information from FSP/FSA.