Relationship between duty factor and external forces in slow recreational runners

Area of Science:

• Biomechanics of running
• Sports science
• Injury prevention

Background:

• Recreational runners exhibit significant variations in running spatiotemporal characteristics.
• Understanding these variations, particularly in slow runners, is key to identifying injury risk factors.

Purpose of the Study:

• To quantify the variability in duty factor (DF) among slow recreational runners.
• To investigate the relationship between DF, stride frequency (SF), and external loading parameters.

Main Methods:

• Spatiotemporal data collected from 23 slow runners during a 5.2 km running event.
• Ground reaction forces (maximal vertical ground reaction force, peak braking force, vertical instantaneous loading rate) measured in 14 runners in a lab setting.
• Multiple linear regression analysis used to assess the impact of DF and SF on external forces.

Main Results:

• Duty factor (DF) varied widely (42.50%–56.49%) among slow recreational runners.
• DF was a significant predictor of maximal vertical ground reaction force (R²=0.755) and peak braking force (R²=0.430).
• Stride frequency (SF) showed a smaller, significant improvement for predicting peak braking force (R² change=0.191); neither DF nor SF predicted vertical instantaneous loading rate.

Conclusions:

• Recreational runners employing higher duty factors and slightly lower stride frequencies experience reduced external forces.
• These biomechanical insights can inform injury prevention strategies for recreational runners prone to overuse injuries.