The effects of load carriage on joint work at different running velocities

Liew, Bernard X. W.; Morris, Susan; Netto, Kevin

doi:10.1016/j.jbiomech.2016.08.012

Cited by 27 publications

(25 citation statements)

References 28 publications

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“…Starting from this initial form, we have used backward stepwise elimination to adapt the equation for each variability metric by removing terms that do not significantly contribute. Our statistical method (mixed-model ANOVA and elimination of terms that do not significantly contribute) is similar to methods used in [ 55 ]. Based on the mixed-model ANOVA, we generated contour plots showing each variability metric versus exoskeleton power and timing.…”

Section: Methodsmentioning

confidence: 99%

Altering gait variability with an ankle exoskeleton

et al. 2018

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Exoskeletons can influence human gait. A healthy gait is characterized by a certain amount of variability compared to a non-healthy gait that has more inherent variability; however which exoskeleton assistance parameters are necessary to avoid increasing gait variability or to potentially lower gait variability below that of unassisted walking are unknown. This study investigated the interaction effects of exoskeleton timing and power on gait variability. Ten healthy participants walked on a treadmill with bilateral ankle-foot exoskeletons under ten conditions with different timing (varied from 36% to 54% of the stride) and power (varied from 0.2 to 0.5 W∙kg-1) combinations. We used the largest Lyapunov exponent (LyE) and maximum Floquet multiplier (FM) to evaluate the stride-to-stride fluctuations of the kinematic time series. We found the lowest LyE at the ankle and a significant reduction versus powered-off with exoskeleton power (summed for both legs) of 0.45 W∙kg-1 and actuation timing at 48% of the stride cycle. At the knee, a significant positive effect of power and a negative interaction effect of power and timing were found for LyE. We found significant positive interaction effects of the square of timing and power for LyE at the knee and hip joints. In contrast, the FM at the ankle increased with increasing power and later timing. We found a significant negative effect of power and a positive interaction effect of power and timing for FM at the knee and no significant effects of any of the exoskeleton parameters for FM at the hip. The ability of the exoskeleton to reduce the LyE at the ankle joint offers new possibilities in terms of altering gait variability, which could have applications for using exoskeletons as rehabilitation devices. Further efforts could examine if it is possible to simultaneously reduce the LyE and FM at one or more lower limb joints.

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Section: Methodsmentioning

confidence: 99%

Altering gait variability with an ankle exoskeleton

et al. 2018

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“…Muscles producing force during shortening (i.e., concentric) generate positive work, while during lengthening contractions (i.e., eccentric) muscles do negative work (Donelan et al, 2002). Recent studies have reported total and joint-specific work and powers increase in response to increased carried load during walking (Grenier et al, 2012;Huang and Kuo, 2014;Wang et al, 2013, Panizzolo et al 2016) and running (Liew et al, 2016) tasks. In these studies, hip muscles perform positive work to stabilize the large moment of inertia of the combined upper body and equipment mass and swing the trailing leg (Winter and Eng, 1995).…”

Section: Introductionmentioning

confidence: 97%

Lower-limb joint work and power are modulated during load carriage based on load configuration and walking speed

Lenton

Doyle

Lloyd

et al. 2019

Journal of Biomechanics

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Soldiers regularly transport loads weighing >20 kg for slow speeds over long durations. These tasks elicit high energetic costs through increasing positive work generated by knee and ankle muscles, which may increase risk of muscular fatigue and decrease combat readiness. This study aimed to determine how modifying where load is borne changes lower-limb joint mechanical work production, and if load magnitude and/or walking speed also affect work production. Twenty Australian soldier participants donned a total of 12 body armor variations: six body armor systems (one standard-issue, two commercially available [cARM1-2], and three prototype [pARM1-3]) and two load magnitudes (15 and 30 kg). In each armor variation, participants completed treadmill walking at two speeds (1.51 and 1.83 m/s). Three-dimensional motion capture and force plate data were acquired and used to estimate joint angles and moments from inverse kinematics and dynamics, respectively. From these, hip, knee, and ankle joint work was computed and compared between armor types and walking speeds. Positive joint work over the stance phase significantly increased with walking speed and carried load, accompanied by 2.3-2.6% shifts in total positive work production from ankle to hip (p<0.05). Compared to using cARM1 with 15 kg of carried load, carrying 30 kg caused significantly greater hip contribution to total positive work, while knee and ankle work decreased. Substantial increases in hip joint contributions to total positive work with increases in walking speed and load magnitude highlight the importance of hip musculature to positive power generation in load carriage walking. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

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“…While these kinetic patterns are indicative of the increased reliance on knee joint to absorb and produce energy during stance 53 , similar adaptations to load are not noted at the hip. The addition of load results in a significant reduction in positive work and an increase of negative work at the hip, evidence of decreased power generation in preparation for propulsion, but increased reliance on the hip for energy absorption.…”

Section: Military Load Carriagementioning

confidence: 85%

Sex Differences in Lower Limb Biomechanics During a Single-Leg Cut with Body Borne Load

Fain¹

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The effects of load carriage on joint work at different running velocities

Cited by 27 publications

References 28 publications

Altering gait variability with an ankle exoskeleton

Altering gait variability with an ankle exoskeleton

Lower-limb joint work and power are modulated during load carriage based on load configuration and walking speed

Sex Differences in Lower Limb Biomechanics During a Single-Leg Cut with Body Borne Load

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