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Related Experiment Videos

Groucho running.

T A McMahon, G Valiant, E C Frederick

    Journal of Applied Physiology (Bethesda, Md. : 1985)
    |June 1, 1987
    PubMed
    Summary
    This summary is machine-generated.

    Running with bent knees reduces body stiffness and shock transmission but increases oxygen consumption by 50%. A new parameter helps differentiate between hard and soft running styles.

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    Area of Science:

    • Biomechanics
    • Human Physiology
    • Sports Science

    Background:

    • Effective vertical stiffness is a key factor in running mechanics.
    • This stiffness naturally increases with running speed.
    • Altering knee flexion can modify running stiffness.

    Purpose of the Study:

    • To investigate the effects of altered knee flexion on running mechanics.
    • To quantify changes in vertical stiffness and shock transmission.
    • To introduce a parameter for classifying running modes.

    Main Methods:

    • Experiments conducted on treadmills and force platforms.
    • Subjects ran in normal and deep-flexed knee postures.
    • Measurement of oxygen consumption and analysis of mechanical shock transmission.

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    Main Results:

    • Running with bent knees significantly reduced effective vertical stiffness.
    • Diminished transmission of mechanical shock from foot to skull observed.
    • Increased oxygen consumption (up to 50%) was required for flexed running.
    • A dimensionless parameter (u omega 0/g) was introduced to define running modes.

    Conclusions:

    • Altering knee flexion is a viable method to reduce running stiffness and shock.
    • This modification comes at a significant metabolic cost (increased O2 consumption).
    • The new parameter (u omega 0/g) effectively distinguishes between hard and soft running styles.