The Claim

Higher body mass increases the optimal ankle-foot orthosis (AFO) stiffness required to reduce energy cost during walking in individuals with bilateral plantarflexor weakness, with a 30% increase in body mass raising optimal stiffness from 3.7 to 4.3 Nm/degree, though this effect is diminished when walking speed is held constant.

Source: The interaction between muscle pathophysiology, body mass, walking speed and ankle foot orthosis stiffness on walking energy cost: a predictive simulation study

What the research says

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Quantitative
1 study reviewed
In plain English

In people with weakened calf muscles, heavier individuals require stiffer ankle-foot orthoses to walk more efficiently, and a 30% increase in body mass raises the optimal stiffness from 3.7 to 4.3 Nm/degree; however, this increase in stiffness becomes less important if walking speed is kept the same.

See the scientific wording

Higher body mass increases optimal AFO stiffness for energy cost reduction in individuals with bilateral plantarflexor weakness, with a 30% increase in body mass raising optimal stiffness from 3.7 to 4.3 Nm/degree, though this effect is diminished when walking speed is fixed.

Why this might work

When a person weighs more, their feet push harder against the ground while walking, which makes the ankle bend too far backward. A stiffer brace is needed to push the ankle forward just enough to keep the knee straight and avoid extra effort from the hips. Without enough stiffness, the ankle collapses and the body uses more energy to keep walking.

Verified mechanismbased on 1 study

What the research says

1 study

  1. Study: The interaction between muscle pathophysiology, body mass, walking speed and ankle foot orthosis stiffness on walking energy cost: a predictive simulation study

    Heavier people with weak calf muscles need stiffer ankle braces to walk without getting tired, but if everyone walks at the same speed, the difference in brace stiffness needed between heavy and light people becomes smaller. This study used computer models to show that’s true.

Score breakdown, mechanism chain, raw evidence, ideal studies needed & 1 supporting studies

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