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Comment
. 2009 Aug 7;42(11):1783-5; author reply 1786-9.
doi: 10.1016/j.jbiomech.2009.03.054. Epub 2009 May 30.

Comment on "Contributions of the individual ankle plantar flexors to support, forward progression and swing initiation during walking" ((Neptune et al., 2001) and "Muscle mechanical work requirements during normal walking: the energetic cost of raising the body's center-of-mass is significant" (Neptune et al., 2004)

Arthur D Kuo, J Maxwell Donelan
Comment

Comment on "Contributions of the individual ankle plantar flexors to support, forward progression and swing initiation during walking" ((Neptune et al., 2001) and "Muscle mechanical work requirements during normal walking: the energetic cost of raising the body's center-of-mass is significant" (Neptune et al., 2004)

Arthur D Kuo et al. J Biomech. .
No abstract available

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Conflict of interest statement

Conflict of Interest Statement

The authors have no financial or personal relationships that could inappropriately influence this work.

Figures

Figure 1
Figure 1
Joint powers from Human and Model. (A) Joint powers for ankle, knee, and hip, from Human data2, plotted vs. time for one stride beginning with heel-strike. Regions 2 and 4 are indicated by shaded areas (R2 and R4). (B) Model joint powers3 (Neptune et al., 2004). Comparison between Human and Model joint powers yielded correlation coefficients r = 0.99 for ankle, r = 0.38 for knee, and r = 0.44 for hip. (C) Net work per stride by Region, comparing two Human data sets against Model’s joint work and net musculotendon (MT) work. Superscripts indicate the following references: 1Winter, 1991; 2Neptune et al., 2001; 3Neptune et al., 2004 (net musculotendon work).
Figure 2
Figure 2
Work performed on body center of mass (COM) by one leg. (A) COM work rate vs. time, comparing two Human data sets against Model. Superscripts indicate the following references: 3Neptune et al., 2004; 4Kuo et al., 2005. Regions 2 and 4 are shown as shaded areas. (B) Summed COM work for both regions, as well as the net musculotendon (MT) work of Model. Both Human data sets show greater work during Region 4 than Region 2. Model’s COM work and MT work do not agree with each other or with Human. (C) Magnitudes of positive and negative COM work per stride, integrated from COM work rate. Positive and negative work should be equal in magnitude for steady walking. Model performs more than twice as much negative work as positive work, indicating computational error.
Figure 3
Figure 3
Vertical ground reaction forces (GRFs), comparing Human and Model. (A) Forces plotted vs. time for Human (Neptune et al., 2004; solid line) and Model (dotted line), with Regions 2 and 4 indicated by shaded areas. Assuming symmetric gait, forces for both legs are shown (thicker lines) for the double support phase beginning at 50% of stride. (B) Average ground reaction forces for Regions 2 and 4 (indicated by horizontal lines in A), and for one full stride. Both Human and Model (3Neptune et al., 2004) produce lower forces during Region 2 than Region 4. Model produces much higher peak forces than Human during Region 4. Assuming symmetry, Model’s average force over a stride is about 10% greater than body weight.
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Comment on

References

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    1. Kuo AD. The six determinants of gait and the inverted pendulum analogy: A dynamic walking perspective. Human Movement Science. 2007;26:617–656. - PubMed
    1. Kuo AD, Donelan JM, Ruina A. Energetic consequences of walking like an inverted pendulum: step-to-step transitions. Exercise and Sport Sciences Reviews. 2005;33:88–97. - PubMed