The modulation of forward propulsion, vertical support, and center of pressure by the plantarflexors during human walking

Francis, Carrie A.; Lenz, Amy L.; Lenhart, Rachel L.; Thelen, Darryl G.

doi:10.1016/j.gaitpost.2013.05.009

Cited by 78 publications

(83 citation statements)

References 20 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…During walking trials, stimulation was introduced to either the gastrocnemius or the soleus starting at 20% (referred to as mid-stance) or 30% (terminal stance) of the gait cycle (Perry, 1992). We note that we have previously shown these stimulation timings correspond well to the normal activation during walking (Francis et al, 2013). …”

Section: Methodssupporting

confidence: 78%

“…Prior computational modeling studies have raised the possibility of the gastrocnemius and soleus inducing differing effects on joint and whole body motion (Francis et al, 2013; Liu et al, 2008; Neptune et al, 2008; Neptune et al, 2004), but conclusions have differed. Pandy et al (2010) used induced acceleration analysis of a 3D gait model and found that the gastrocnemius and soleus induced disparate actions at the hip (gastrocnemius flexion, soleus extension), but the same action at the knee (extension) and ankle (plantarflexion).…”

Section: Discussionmentioning

confidence: 99%

“…Both translational and rotational dampers were used to emulate a fixed foot during foot flat (10-35% of gait cycle), allowing forward progression of center of pressure for early stimulation as observed experimentally by Francis et al (2013). A translational damper at the center of pressure was used to emulate a point constraint after heel off (>35% of gait cycle), which restricted progression of center of pressure (Francis et al 2013). Kinematic changes were assessed by comparing joint angle trajectories to those seen in the nominal simulation, as was done experimentally.…”

Section: Methodsmentioning

confidence: 99%

See 2 more Smart Citations

Empirical evaluation of gastrocnemius and soleus function during walking

Lenhart

Francis

Lenz

et al. 2014

Journal of Biomechanics

Self Cite

View full text Add to dashboard Cite

Distinguishing gastrocnemius and soleus muscle function is relevant for treating gait disorders in which abnormal plantarflexor activity may contribute to pathological movement patterns. Our objective was to use experimental and computational analysis to determine the influence of gastrocnemius and soleus activity on lower limb movement, and determine if anatomical variability of the gastrocnemius affected its function. Our hypothesis was that these muscles exhibit distinct functions, with the gastrocnemius inducing limb flexion and the soleus inducing limb extension. To test this hypothesis, the gastrocnemius or soleus of twenty healthy participants was electrically stimulated for brief periods (90 ms) during mid-or terminal stance of a random gait cycle. Muscle function was characterized by the induced change in sagittal pelvis, hip, knee, and ankle angles occurring during the 200 ms after stimulation onset. Results were corroborated with computational forward dynamic gait models, by perturbing gastrocnemius or soleus activity during similar portions of the gait cycle. Mid- and terminal stance gastrocnemius stimulation induced posterior pelvic tilt, hip flexion and knee flexion. Mid-stance gastrocnemius stimulation also induced ankle dorsiflexion. In contrast, mid-stance soleus stimulation induced anterior pelvic tilt, knee extension and plantarflexion, while late-stance soleus stimulation induced relatively little change in motion. Model predictions of induced hip, knee, and ankle motion were generally in the same direction as the experiments, though the gastrocnemius’ results were shown to be quite sensitive to its knee-to-ankle moment arm ratio.

show abstract

Section: Methodssupporting

confidence: 78%

Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

See 1 more Smart Citation

Empirical evaluation of gastrocnemius and soleus function during walking

Lenhart

Francis

Lenz

et al. 2014

Journal of Biomechanics

Self Cite

View full text Add to dashboard Cite

show abstract

“…There is considerable current interest in the decomposition of the GRF to investigate the function of different muscles [17,19,20] and the analysis of the IP model has been extended to evaluate the contribution of the hip actuator to the GRF. Figure 1a shows the free body diagram for the simple IP model.…”

Section: Introductionmentioning

confidence: 99%

The strengths and weaknesses of inverted pendulum models of human walking

2015

View full text Add to dashboard Cite

-An investigation into the kinematic and kinetic predictions of two "inverted pendulum" (IP) models of gait was undertaken. The first model consisted of a single leg, with anthropometrically correct mass and moment of inertia, and a point mass at the hip representing the rest of the body. A second model incorporating the physiological extension of a head-arms-trunk (HAT) segment, held upright by an actuated hip moment, was developed for comparison. Simulations were performed, using both models, and quantitatively compared with empirical gait data. There was little difference between the two models' predictions of kinematics and ground reaction force (GRF). The models agreed well with empirical data through mid-stance (20-40% of the gait cycle) suggesting that IP models adequately simulate this phase (mean error less than one standard deviation). IP models are not cyclic, however, and cannot adequately simulate double support and stepto-step transition. This is because the forces under both legs augment each other during double support to increase the vertical GRF. The incorporation of an actuated hip joint was the most novel change and added a new dimension to the classic IP model. The hip moment curve produced was similar to those measured during experimental walking trials. As a result, it was interpreted that the primary role of the hip musculature in stance is to keep the HAT upright. Careful consideration of the differences between the models throws light on what the different terms within the GRF equation truly represent.

show abstract

“…Whilst this is unlikely to affect the overall dynamics of the system (it is still a one DOF system) it will allow an investigation of the extent to which hip flexor and extensor activity measured using inverse dynamics during normal walking can be attributed to the requirements of an IP model. There is considerable current interest in the decomposition of the GRF to investigate the function of different muscles (Anderson & Pandy, 2003;Francis et al, 2013;Liu et al, 2006) and the analysis of the IP model has been extended to evaluate the contribution of the hip actuator to the GRF.…”

Section: Literaturementioning

confidence: 99%