title: Foot speed, foot-strike and footwear: linking gait mechanics and running ground reaction forces.
abstract: Running performance, energy requirements and musculoskeletal stresses are directly related to the action-reaction forces between the limb and the ground. For human runners, the force-time patterns from individual footfalls can vary considerably across speed, foot-strike and footwear conditions. Here, we used four human footfalls with distinctly different vertical force-time waveform patterns to evaluate whether a basic mechanical model might explain all of them. Our model partitions the body's total mass (1.0 Mb) into two invariant mass fractions (lower limb=0.08, remaining body mass=0.92) and allows the instantaneous collisional velocities of the former to vary. The best fits achieved (R(2) range=0.95-0.98, mean=0.97 ± 0.01) indicate that the model is capable of accounting for nearly all of the variability observed in the four waveform types tested: barefoot jog, rear-foot strike run, fore-foot strike run and fore-foot strike sprint. We conclude that different running ground reaction force-time patterns may have the same mechanical basis.
authors.affiliation: Southern Methodist University, Locomotor Performance Laboratory, 5538 Dyer Street, Department of Applied Physiology and Wellness, Dallas, TX 75206, USA.
authors.forename: Kenneth P
authors.initials: KP
authors.lastname: Clark
authors.affiliation: Southern Methodist University, Locomotor Performance Laboratory, 5538 Dyer Street, Department of Applied Physiology and Wellness, Dallas, TX 75206, USA.
authors.forename: Laurence J
authors.initials: LJ
authors.lastname: Ryan
authors.affiliation: Southern Methodist University, Locomotor Performance Laboratory, 5538 Dyer Street, Department of Applied Physiology and Wellness, Dallas, TX 75206, USA pweyand@smu.edu.
authors.forename: Peter G
authors.initials: PG
authors.lastname: Weyand
mesh_terms: D001696:Biomechanical Phenomena; D005528:Foot / Q000502:physiology*; D005684:Gait; D006801:Humans; D035002:Lower Extremity / Q000502:physiology; D008962:Models, Theoretical; D012420:Running; D012775:Shoes
keywords: Barefoot running; Biomechanics; Force-motion; Running performance