Hitting a support surface at unexpected height during walking induces loading transients

Linden, M.H. van der; Hendricks, Henk T.; Bloem, Bastiaan R.; Duysens, Jacques

doi:10.1016/j.gaitpost.2008.08.017

Cited by 16 publications

(9 citation statements)

References 27 publications

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“…losses inherent to impacts, increased muscle recruitment) and an increased risk (shock transmission). Such an increased impact peak has also been observed in walkers hitting a support surface at an unexpected height (van der Linden et al, 2009). The impact phase during walking is sometimes characterized by an early 'transient' loading peak.…”

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confidence: 71%

“…The impact phase during walking is sometimes characterized by an early 'transient' loading peak. This transient peak occurred more frequently when subjects were unaware of the level of the support surface and was related to shock absorption at foot contact and to a mismatch between the produced and, according to the authors, required muscle force at the moment of impact (van der Linden et al, 2009). Furthermore, we observed 33% decreased leg stiffness and 6% decreased angle of attack at CL (compared with VL).…”

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confidence: 95%

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Leg adjustments during running across visible and camouflaged incidental changes in ground level

Müller

Ernst

Blickhan

2012

Journal of Experimental Biology

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SUMMARYDuring running in a natural environment, humans must routinely negotiate varied and unpredictable changes in ground level. To prevent a fall, changes in ground level, especially those that are invisible, require a quick response of the movement system within a short time. For 11 subjects we investigated two consecutive contacts during running across visible (drop of 0, 5 and 10cm) and camouflaged (drop of 0 and 10cm) changes in ground level. For both situations, we found significant variances in their leg parameters and ground reaction forces (GRFs) during the perturbed second contact but also one step ahead, in the unperturbed first contact. At visible first contact, humans linearly adapt their GRF to lower and smooth their centre of mass. During the camouflaged situation, the GRF also decreased, but it seems that the runners anticipate a drop of approximately 5-10cm. The GRF increased with drop height during the visible perturbed second contact. At the camouflaged second contact, GRFs differed noticeably from the observed reaction when crossing a similar visible drop, whereas the contact time decreased and the initial impact peak increased. This increased impact can be interpreted as a purely mechanical contribution to cope with the event. Furthermore, we observed an increased angle of attack and leg length with drop height for both situations. This is in accordance with results observed in birds running over a track with an unexpected drop, and suggests that adaptations in swing leg retraction form part of the strategy for running across uneven ground.

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confidence: 71%

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confidence: 95%

Leg adjustments during running across visible and camouflaged incidental changes in ground level

Müller

Ernst

Blickhan

2012

Journal of Experimental Biology

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“…The human gait data involves impact forces at the leg touch-down, which introduces an additional behaviour in the GRF pattern [30,35,36]. In order to see the influence of the impact on VP, we are presenting our recorded data in two ways.…”

Section: Experimental Methodsmentioning

confidence: 99%

Postural stability in human running with step-down perturbations: an experimental and numerical study

et al. 2020

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Postural stability is one of the most crucial elements in bipedal locomotion. Bipeds are dynamically unstable and need to maintain their trunk upright against the rotations induced by the ground reaction forces (GRFs), especially when running. Gait studies report that the GRF vectors focus around a virtual point above the centre of mass (VP A ), while the trunk moves forward in pitch axis during the stance phase of human running. However, a recent simulation study suggests that a virtual point below the centre of mass (VP B ) might be present in human running, because a VP A yields backward trunk rotation during the stance phase. In this work, we perform a gait analysis to investigate the existence and location of the VP in human running at 5 m s −1 , and support our findings numerically using the spring-loaded inverted pendulum model with a trunk. We extend our analysis to include perturbations in terrain height (visible and camouflaged), and investigate the response of the VP mechanism to step-down perturbations both experimentally and numerically. Our experimental results show that the human running gait displays a VP B of ≈−30 cm and a forward trunk motion during the stance phase. The camouflaged step-down perturbations affect the location of the VP B . Our simulation results suggest that the VP B is able to encounter the step-down perturbations and bring the system back to its initial equilibrium state.

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“…For walking on uneven ground, when human walkers encounter a drop, they modulate their GRF kinetics proportional with the drop height not only in the perturbation step, but also in the approach step to the perturbation ( Müller, et al, 2014 ). However, the quality and quantity of the kinetic and kinematic adaptations or reactions to external perturbations are context-specific ( Müller, et al, 2014 ; van der Linden, et al 2009 , 2007 ). While these studies have analysed human walking with various trunk configurations or adaptive and reactive kinetic mechanisms in pre-perturbation and perturbation contacts and made comparisons with avian locomotor behaviour, to our knowledge, kinetic and kinematic adaptations when stepping down (perturbation) and in pre- and post-perturbation steps with different bent postures have not been investigated yet.…”

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confidence: 99%

Effects of altered sagittal trunk orientation on kinetic pattern in able-bodied walking on uneven ground

Aminiaghdam

Rode

2017

Biology Open

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Studies of disturbed human locomotion often focus on the dynamics of the gait when either posture, movement or surface is perturbed. Yet, the interaction effects of variation of trunk posture and ground level on kinetic behaviour of able-bodied gait have not been explored. For 12 participants we investigated the kinetic behaviour, as well as velocity and contact time, across four steps including an unperturbed step on level ground, pre-perturbation, perturbation (10-cm drop) and post-perturbation steps while walking with normal speed with four postures: regular erect, with 30°, 50° and maximal sagittal trunk flexion (70°). Two-way repeated measures ANOVAs detected significant interactions of posture×step for the second peak of the vertical ground reaction force (GRF), propulsive impulse, contact time and velocity. An increased trunk flexion was associated with a systematic decrease of the second GRF peak during all steps and with a decreased contact time and an increased velocity across steps, except for the perturbation step. Pre-adaptations were more pronounced in the approach step to the drop in regular erect gait. With increased trunk flexion, walking on uneven ground exhibited reduced changes in GRF kinetic parameters relative to upright walking. It seems that in trunk-flexed gaits the trunk is used in a compensatory way during the step-down to accommodate changes in ground level by adjusting its angle leading to lower variations in centre of mass height. Exploitation of this mechanism resembles the ability of small birds in adjusting their zig-zag-like configured legs to cope with changes in ground level.

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Hitting a support surface at unexpected height during walking induces loading transients

Cited by 16 publications

References 27 publications

Leg adjustments during running across visible and camouflaged incidental changes in ground level

Leg adjustments during running across visible and camouflaged incidental changes in ground level

Postural stability in human running with step-down perturbations: an experimental and numerical study

Effects of altered sagittal trunk orientation on kinetic pattern in able-bodied walking on uneven ground

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