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1st Joint ESMAC-GCMAS Meeting - Análise de Marcha

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Results<br />

At all speeds, the net influence of stance-si<strong>de</strong> muscles was to slow forward progression during<br />

loading response and early single-limb support, and to propel the body forward during late<br />

single-limb support and preswing (Fig. 1). Braking<br />

and propulsion by stance-si<strong>de</strong> muscles increased<br />

with walking speed. Individual muscle<br />

contributions to progression reflected this trend<br />

(Fig. 2).<br />

Discussion<br />

We generated subject-specific, muscle-actuated,<br />

3D simulations of a child walking at three speeds.<br />

Increased walking speed arose from greater<br />

propulsion by hip flexors and ankle plantarflexors<br />

during late single-limb support and preswing. A<br />

Figure 1. Average fore-aft induced<br />

counterintuitive finding was that knee extensors generated<br />

accelerations from stance-si<strong>de</strong> muscles.<br />

larger braking effects at higher speeds. The braking<br />

effects of dorsiflexors at the slowest and fastest walking<br />

speed were similar, suggesting unusually high dorsiflexor forces during slow walking. This<br />

finding is consistent with a prolonged internal dorsiflexion moment computed from the<br />

subject’s experimental data during slow walking.<br />

These results suggest that therapies aimed at increasing hip flexor and plantarflexor strength<br />

may be beneficial for patients with limited walking speed, since these two muscle groups are<br />

primarily responsible for increasing gait speed.<br />

Figure 2. Major muscle contributors to braking<br />

and propulsion. Top panel: Vasti and<br />

dorsiflexors were the primary sources of braking<br />

during loading response. Second panel: Vasti,<br />

gastrocnemius, and soleus provi<strong>de</strong>d braking<br />

during early single-limb support, with some<br />

assistance from rectus femoris (not shown).<br />

Third panel: Gastrocnemius and iliopsoas<br />

propelled the body forward during late singlelimb<br />

support. Smaller contributions from gluteus<br />

minimus, medial hamstrings, peroneal muscles<br />

(not shown), soleus, and dorsiflexors also<br />

assisted in propulsion, but were inconsistent<br />

across walking speeds. Bottom panel:<br />

Gastrocnemius, soleus, and iliopsoas provi<strong>de</strong>d<br />

propulsion during preswing, with smaller<br />

contributions from medial hamstrings and<br />

peroneal muscles that were inconsistent across<br />

walking speeds.<br />

References<br />

[1] <strong>de</strong>n Otter, et al, (2004), Gait Posture, 19, 270-278<br />

[2] Neptune et al, (2004), Gait Posture, 19, 194-205<br />

[3] Liu et al, (in press), J Biomech<br />

[4] Thelen and An<strong>de</strong>rson, (2006), J Biomech, 39, 6, 1107-1115<br />

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