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My question is regarding the friction use trace (ratio between forward and downward forces) for normal stepping. I have noticed in two studies investigating slip-and-falls (Perkins and Wilson, 1983 & Strandberg 1983) that for subjects taking a normal step, the following occurs: first, heel-strike presents the expected generation of a force in a forward direction and then toe-off generates a backward force. However in the friction use traces of the papers I mentioned above, I see a quick, sharp peak in the backward direction during heel-strike. The force rapidly changes direction and goes forward again. Is this a consistent feature of friction use traces for normal walking?
Can anyone explain what causes this peak? An advisor and I discussed it, and we thought it might be attributable to one of three things: a subject who digs his heels backward at heel strike, a backward force generated by hip extension as the body's center of mass is transferred over the leading foot, or perhaps artifact. Any information would be much appreciated.
Rachel Beyer
Can anyone explain what causes this peak? An advisor and I discussed it, and we thought it might be attributable to one of three things: a subject who digs his heels backward at heel strike, a backward force generated by hip extension as the body's center of mass is transferred over the leading foot, or perhaps artifact. Any information would be much appreciated.
Rachel Beyer