How Does Ankle Mechanical Stiffness Change as a Function of Muscle Activation in Standing and During the Late Stance of Walking?

Joshi, Varun; Rouse, Elliott J.; Claflin, E. S.; Krishnan, Chandramouli

doi:10.1109/tbme.2021.3117516

Cited by 7 publications

(6 citation statements)

References 30 publications

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“…This reduced activation could help delay fatigue 53 . We also found that the activation level showed a reasonable correlation 45 , 64 with the metabolic cost. Further research is needed to optimize the exoskeleton parameters for personalized squat assistance using muscle activation as an objective function (as an alternative to metabolic cost).…”

Section: Discussionsupporting

confidence: 62%

“…The muscle activation level of the RF muscle was also reduced compared to the no-device condition. We also identified a moderately high and significant correlation 45 , 46 between metabolic cost and quadriceps muscle activation level.…”

Section: Discussionmentioning

confidence: 72%

“…We performed Pearson’s correlation analysis 45 , 64 , 82 between the metabolic cost and the activation level of muscle synergy and RF muscle. Before conducting the correlation analysis, we normalized the metabolic cost and the muscle activation-related data from 0 to 1.…”

Section: Methodsmentioning

confidence: 99%

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Muscle coordination and recruitment during squat assistance using a robotic ankle–foot exoskeleton

Jeong

Haghighat

Kantharaju

et al. 2023

Sci Rep

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Squatting is an intensive activity routinely performed in the workplace to lift and lower loads. The effort to perform a squat can decrease using an exoskeleton that considers individual worker’s differences and assists them with a customized solution, namely, personalized assistance. Designing such an exoskeleton could be improved by understanding how the user’s muscle activity changes when assistance is provided. This study investigated the change in the muscle recruitment and activation pattern when personalized assistance was provided. The personalized assistance was provided by an ankle–foot exoskeleton during squatting and we compared its effect with that of the no-device and unpowered exoskeleton conditions using previously collected data. We identified four main muscle recruitment strategies across ten participants. One of the strategies mainly used quadriceps muscles, and the activation level corresponding to the strategy was reduced under exoskeleton assistance compared to the no-device and unpowered conditions. These quadriceps dominant synergy and rectus femoris activations showed reasonable correlations (r = 0.65, 0.59) to the metabolic cost of squatting. These results indicate that the assistance helped reduce quadriceps activation, and thus, the metabolic cost of squatting. These outcomes suggest that the muscle recruitment and activation patterns could be used to design an exoskeleton and training methods.

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Section: Discussionsupporting

confidence: 62%

Section: Discussionmentioning

confidence: 72%

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Muscle coordination and recruitment during squat assistance using a robotic ankle–foot exoskeleton

Jeong

Haghighat

Kantharaju

et al. 2023

Sci Rep

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“…When we included Day3 validation data, the correlation values increased to 0.72 for 60-90s and 0.74 for 210-270s, a high positive correlation 42 . Our definition of reasonable correlation values is consistent with the definition from the research guide for medical research 42 and previous studies for physiological measurement correlation in which values of 0.59-0.64 were used for reasonable correlation 26 , 44 , 45 . For instance, changes in integrated EMG and muscle synergy activation were considered to have a high correlation to change in metabolic cost with a correlation coefficient value of 0.64 26 .…”

Section: Discussionsupporting

confidence: 56%

Foot contact forces can be used to personalize a wearable robot during human walking

Jacobson

Kantharaju

Jeong

et al. 2022

Sci Rep

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Individuals with below-knee amputation (BKA) experience increased physical effort when walking, and the use of a robotic ankle-foot prosthesis (AFP) can reduce such effort. The walking effort could be further reduced if the robot is personalized to the wearer using human-in-the-loop (HIL) optimization of wearable robot parameters. The conventional physiological measurement, however, requires a long estimation time, hampering real-time optimization due to the limited experimental time budget. This study hypothesized that a function of foot contact force, the symmetric foot force-time integral (FFTI), could be used as a cost function for HIL optimization to rapidly estimate the physical effort of walking. We found that the new cost function presents a reasonable correlation with measured metabolic cost. When we employed the new cost function in HIL ankle-foot prosthesis stiffness parameter optimization, 8 individuals with simulated amputation reduced their metabolic cost of walking, greater than 15% (p < 0.02), compared to the weight-based and control-off conditions. The symmetry cost using the FFTI percentage was lower for the optimal condition, compared to all other conditions (p < 0.05). This study suggests that foot force-time integral symmetry using foot pressure sensors can be used as a cost function when optimizing a wearable robot parameter.

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“…Separate regression analyses were performed using the data from the reconstructed limb, nonreconstructed limb, symmetry values, and the change scores to comprehensively understand the contributions of knee flexion angle and vGRF to peak knee extension moment during gait. We adopted an inclusive statistical approach where both classical and Bayesian regression analyses were performed to measure statistical significance ( P value) and the Bayes factor (BF 10 ), respectively (20)(21)(22)(23)(24)(25). More details regarding the Bayesian analysis and how to interpret the results of this analysis are provided in the JASP manual (http://static.jasp-stats.org/Manuals/Bayesian_Guide_v0_12_2_ 1.pdf).…”

Section: Methodsmentioning

confidence: 99%

Mechanical Factors Contributing to Altered Knee Extension Moment during Gait after ACL Reconstruction: A Longitudinal Analysis

Krishnan

Johnson

Palmieri-Smith

2022

Medicine &Amp; Science in Sports &Amp; Exercise

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PurposeThis study aimed to comprehensively examine the extent to which knee flexion angle at initial contact, peak knee flexion angle, and vertical ground reaction force (vGRF) contribute to knee extension moments during gait in individuals with anterior cruciate ligament (ACL) reconstruction.MethodsOverground gait biomechanics were evaluated in 26 participants with ACL reconstruction at three time points (about 2, 4, and 6 months after the surgery). Knee flexion angle at initial contact, peak knee flexion angle, peak vGRF, and peak knee extension moment were calculated for each limb during the early stance phase of gait for all three time points. A change score from baseline (time point 2 − time point 1 and time point 3 − time point 1) along with limb symmetry values (ACL − non-ACL limb values) was also calculated for these variables. Multiple linear regressions utilizing classical and Bayesian interference methods were used to determine the contribution of knee flexion angle and vGRF to knee extension moment during gait.ResultsPeak knee flexion angle and peak vGRF positively contributed to knee extension moment during gait in both the reconstructed (R2 = 0.767, P < 0.001) and nonreconstructed limbs (R2 = 0.815, P < 0.001). Similar results were observed for the symmetry values (R2 = 0.673, P < 0.001) and change scores (R2 = 0.731–0.883; all P < 0.001), except that the changes in knee flexion angle at initial contact also contributed to the model using the change scores in the nonreconstructed limb (time point 2 − time point 1: R2 = 0.844, P < 0.001; time point 3 − time point 1: R2 = 0.883, P < 0.001). Bayesian regression evaluating the likelihood of these prediction models showed that there was decisive evidence favoring the alternative model over the null model (all Bayes factors >1000). Standardized β coefficients indicated that changes in knee flexion angle had a greater impact (>2×) on knee extension moments than vGRF at both time points in both limbs (βvGRF = 0.204–0.309; βkneeflexion = 0.703–0.831).ConclusionsThe findings indicate that both knee flexion angle and peak vGRF positively contribute to altered knee extension moments during gait, but the contribution of knee flexion angle is much greater than vGRF. Therefore, treatment strategies targeting these variables may improve knee loading after ACL reconstruction.

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How Does Ankle Mechanical Stiffness Change as a Function of Muscle Activation in Standing and During the Late Stance of Walking?

Cited by 7 publications

References 30 publications

Muscle coordination and recruitment during squat assistance using a robotic ankle–foot exoskeleton

Muscle coordination and recruitment during squat assistance using a robotic ankle–foot exoskeleton

Foot contact forces can be used to personalize a wearable robot during human walking

Mechanical Factors Contributing to Altered Knee Extension Moment during Gait after ACL Reconstruction: A Longitudinal Analysis

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