Lower Limb Stiffness During a Loaded Walk and Run Over Different Surfaces

Area of Science:

• Biomechanics
• Human Movement Science
• Sports Medicine

Background:

• Understanding the impact of external loads and surface properties on human locomotion is crucial for injury prevention.
• Previous research has explored factors affecting ground reaction forces and lower limb stiffness, but comprehensive analysis across sexes, gaits, loads, and surfaces is limited.

Purpose of the Study:

• To quantify the effects of body-borne load and surface type on vertical ground reaction forces (vGRFs) and lower limb stiffness during walking and running.
• To compare biomechanical responses between males and females under various locomotion conditions.

Main Methods:

• Nine males and nine females performed walking (1.3 m/s) and running (4.5 m/s) trials.
• Trials were conducted with and without a 15 kg body-borne load on both firm and soft foam surfaces.
• Vertical ground reaction forces (vGRFs) and lower limb joint stiffness were measured and analyzed using linear mixed models.

Main Results:

• Loaded walking and running significantly increased vGRFs and lower limb stiffness (P < .016 and P < .033, respectively).
• The foam surface increased peak vGRF and knee stiffness during both gaits, and leg/ankle stiffness during running (P < .025).
• Males exhibited greater peak vGRF and hip/ankle stiffness during walking, and greater knee stiffness on foam during running compared to females.

Conclusions:

• Loaded walking and running, along with locomotion on compliant foam surfaces, may increase the risk of lower limb injuries due to elevated vGRFs and stiffness.
• Sex-specific differences in biomechanical responses suggest varying injury susceptibility, with males potentially at higher risk on foam surfaces.