Step frequency and lower extremity loading during running.

Area of Science:

• Biomechanics
• Sports Medicine
• Orthopedics

Background:

• Tibial stress fractures are common in runners.
• High impact forces and loading rates are associated with stress fractures.
• Current strategies to reduce injury risk often focus on training modifications.

Purpose of the Study:

• To determine if increasing step frequency at a constant running velocity reduces lower extremity loading.
• To identify the optimal step frequency for minimizing loading variables.
• To investigate the relationship between step frequency and variables linked to tibial stress fractures.

Main Methods:

• Ten male runners ran at a controlled velocity (2.5 m/s) on a force plate.
• Five step frequencies were tested: preferred, -15%, -30%, +15%, +30% of preferred.
• Vertical impact peak (VIP), vertical instantaneous loading rate (VILR), and vertical average loading rate (VALR) were measured from ground reaction forces.

Main Results:

• Significant differences in lower extremity loading variables were observed across the tested step frequencies.
• Quadratic regression identified minimum loading frequencies at 17.25% (VIP), 17.55% (VILR), and 18.07% (VIAR) above preferred step frequency.
• Increased step frequency demonstrably reduced loading variables.

Conclusions:

• Increasing step frequency above the preferred rate can decrease lower extremity loading during running.
• Adopting a higher step frequency may be a practical strategy to reduce the risk of tibial stress fractures.
• Further research could explore long-term effects and individual variations in response.