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Journal of Experimental Biology partnership with Dryad

Slipping, sliding and stability: locomotor strategies for overcoming low-friction surfaces
Andrew J. Clark, Timothy E. Higham

SUMMARY

Legged terrestrial animals must avoid falling while negotiating unexpected perturbations inherent to their structurally complex environments. Among humans, fatal and nonfatal injuries frequently result from slip-induced falls precipitated by sudden unexpected encounters with low-friction surfaces. Although studies using walking human models have identified some causes of falls and mechanisms underlying slip prevention, it is unclear whether these apply to various locomotor speeds and other species. We used high-speed video and inverse dynamics to investigate the locomotor biomechanics of helmeted guinea fowl traversing slippery surfaces at variable running speeds (1.3–3.6 m s–1). Falls were circumvented when limb contact angles exceeded 70 deg, though lower angles were tolerated at faster running speeds (>3.0 m s–1). These prerequisites permitted a forward shift of the body's center of mass over the limb's base of support, which kept slip distances below 10 cm (the threshold distance for falls) and maximized the vertical ground reaction forces, thus facilitating limb retraction and the conclusion of the stance phase. These postural control strategies for slip avoidance parallel those in humans, demonstrating the applicability of these strategies across locomotor gaits and the potential for guinea fowl as an insightful model for invasive approaches to understanding limb neuromuscular control on slippery surfaces.

FOOTNOTES

  • LIST OF ABBREVIATIONS

    BOS
    base of support
    BW
    body weight
    COM
    center of mass
    COP
    center of pressure
    GRF
    ground reaction force
    PBF
    peak braking force
    PCA
    principal components analysis
    PMF
    peak medial force
    PP
    polypropylene
    PPF
    peak propulsive force
    PVF
    peak vertical force
    R
    out-moment arm
    SP
    sandpaper
    TMP
    tarsometatarsophalangeal joint
    WBC
    wing–body connection
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