Biology subjects

De Groote, F.

Publications and source records attributed to De Groote, F..

24 records · Page 2Linked to original sources

bioRxiv2020

Validation of a smartphone embedded inertial measurement unit for measuring postural stability in older adults

BackgroundIdentifying older adults with increased fall risk due to poor postural control on a large scale is only possible through omnipresent and low cost measuring devices such as the inertial measurement units (IMU) embedded in smartphones. However, the correlation between smartphone measures of postural stability and state-of-the-art force plate measures has never been assessed in a large sample allowing us to take into account age as a covariate. Research questionHow reliably can postural stability be measured with a smartphone embedded IMU in comparison to a force plate? MethodsWe assessed balance in 97 adults aged 50 to 90 years in four different conditions (eyes open, eyes closed, semi-tandem and dual-task) in the anterio-posterior and medio-lateral directions. We used six different parameters (root mean square and average absolute value of COP displacement, velocity and acceleration) for the force plate and two different parameters (root mean square and average absolute value of COM acceleration) for the smartphone. ResultsTest-retest reliability was smaller for the smartphone than for the force plate (intra class correlation) but both devices could equally well detect differences between conditions (similar Cohens d). Parameters from the smartphone and the force plate, with age regressed out, were moderately correlated (robust correlation coefficients of around 0.5). SignificanceThis study comprehensively documents test-retest reliability and effect sizes for stability measures obtained with a force plate and smartphone as well as correlations between force plate and smartphone measures based on a large sample of older adults. Our large sample size allowed us to reliably determine the strength of the correlations between force plate and smartphone measures. The most important practical implication of our results is that more repetitions or longer trials are required when using a smartphone instead of a force plate to assess balance. HighlightsO_LIWe compared balance measures simultaneously obtained from a phone and a force plate C_LIO_LIFor precision purposes, we included a large group of older participants (N=97). C_LIO_LIUsing age as covariate, we found a moderate correlation across the two devices. C_LIO_LIIntra-class correlation coefficients were smaller for the smartphone. C_LIO_LIBalance assessment with smartphones requires longer trials compared to force plates. C_LI

bioengineering↗

bioRxiv2020

Achilles tendon stiffness minimizes the energy cost in simulations of walking in older but not in young adults

Both Achilles tendon stiffness and walking patterns influence the energy cost of walking, but their relative contributions remain unclear. These independent contributions can only be investigated using simulations. We created models for 16 young (24{+/-}2 years) and 15 older (75{+/-}4 years) subjects, with individualized (using optimal parameter estimations) and generic triceps surae muscle-tendon parameters. We varied Achilles tendon stiffness and calculated the energy cost of walking. Both in young and older adults, Achilles tendon stiffness independently contributed to the energy cost of walking. However, overall, a 25% increase in Achilles tendon stiffness increased the triceps surae and whole-body energy cost of walking with approximately 7% and 1.5%, respectively. Therefore, the influence of Achilles tendon stiffness is rather limited. Walking patterns also independently contributed to the energy cost of walking because the plantarflexor (including, but not limited to the triceps surae) energy cost of walking was lower in older than in young adults. Hence, training interventions should probably rather target specific walking patterns than Achilles tendon stiffness to decrease the energy cost of walking. However, based on the results of previous experimental studies, we expected that the calculated hip extensor and whole-body energy cost of walking would be higher in older than in young adults. This was not confirmed in our results. Future research might therefore assess the contribution of the walking pattern to the energy cost of walking by individualizing maximal isometric muscle force and by using three-dimensional models of muscle contraction. Summary statementAchilles tendon stiffness and walking patterns independently contribute to the energy cost in simulations of walking in young and older adults. The influence of Achilles tendon stiffness is rather small.

physiology↗

bioRxiv2019

Habitual foot strike pattern does not affect simulated Triceps Surae muscle metabolic energy consumption during running

Foot strike pattern affects ankle joint work and Triceps Surae muscle-tendon dynamics during running. Whether these changes in muscle-tendon dynamics also affect Triceps Surae muscle energy consumption is still unknown. In addition, as the Triceps Surae muscle accounts for a substantial amount of the whole body metabolic energy consumption, changes in Triceps Surae energy consumption may affect whole body metabolic energy consumption. However, direct measurements of muscle metabolic energy consumption during dynamic movements is hard. Model-based approaches can be used to estimate individual muscle and whole body metabolic energy consumption based on Hill type muscle models. In this study, we use an integrated experimental and dynamic optimization approach to compute muscle states (muscle forces, lengths, velocities, excitations and activations) of 10 habitual mid-/forefoot striking and 9 habitual rearfoot striking runners while running at 10 and 14 km/h. The Achilles tendon stiffness of the musculoskeletal model was adapted to fit experimental ultrasound data of the Gastrocnemius medialis muscle during ground contact. Next, we calculated Triceps Surae muscle and whole body metabolic energy consumption using four different metabolic energy models provided in literature. Neither Triceps Surae metabolic energy consumption (p > 0.35), nor whole body metabolic energy consumption (p > 0.14) was different between foot strike patterns, regardless of the energy model used or running speed tested. Our results provide new evidence that mid-/forefoot and rearfoot strike pattern are metabolically equivalent.

physiology↗

bioRxiv2019

Ultrasound-based optimal parameter estimation improves assessment of calf muscle-tendon interaction during walking

We present and evaluate a new approach to estimate calf muscle-tendon parameters and calculate calf muscle-tendon function during walking. We used motion analysis, ultrasound, and EMG data of the calf muscles collected in six young and six older adults during treadmill walking as inputs to a new optimal estimation algorithm. We used estimated parameters or scaled generic parameters in an existing approach to calculate muscle fiber lengths and activations. We calculated the fit with experimental data in terms of root mean squared differences (RMSD) and coefficients of determination (R2). We also calculated the calf muscle metabolic energy cost. RMSD between measured and calculated fiber lengths and activations decreased and R2 increased when estimating parameters compared to using scaled generic parameters. Moreover, R2 between measured and calculated gastrocnemius medialis fiber length and soleus activations increased by 19 % and 70 %, and calf muscle metabolic energy decreased by 25% when using estimated parameters compared to using scaled generic parameters at speeds not used for estimation. This new approach estimates calf muscle-tendon parameters in good accordance with values reported in literature. The approach improves calculations of calf muscle-tendon interaction during walking and highlights the importance of individualizing calf muscle-tendon parameters.

bioengineering↗

bioRxiv2019

Physics-based predictive simulations to explore the differential effects of motor control and musculoskeletal deficits on gait dysfunction in cerebral palsy: a retrospective case study

Model-based simulations of walking have the theoretical potential to support clinical decision making by predicting the functional outcome of treatments in terms of walking performance. Yet before using such simulations in clinical practice, their ability to identify the main treatment targets in specific patients needs to be demonstrated. In this study, we generated predictive simulations of walking with a medical imaging based neuro-musculoskeletal model of a child with cerebral palsy presenting crouch gait. We explored the influence of altered muscle-tendon properties, reduced neuromuscular control complexity, and spasticity on gait function in terms of joint kinematics, kinetics, muscle activity, and metabolic cost of transport. We modeled altered muscle-tendon properties by personalizing Hill-type muscle-tendon parameters based on data collected during functional movements, simpler neuromuscular control by reducing the number of independent muscle synergies, and spasticity through delayed muscle activity feedback from muscle force and force rate. Our simulations revealed that, in the presence of aberrant musculoskeletal geometries, altered muscle-tendon properties rather than reduced neuromuscular control complexity and spasticity were the primary cause of the crouch gait pattern observed for this child, which is in agreement with the clinical examination. These results suggest that muscle-tendon properties should be the primary target of interventions aiming to restore a more upright gait pattern for this child. This suggestion is in line with the gait analysis following muscle-tendon property and bone deformity corrections. The ability of our simulations to distinguish the contribution of different impairments on walking performance opens the door for identifying targeted treatment strategies with the aim of designing optimized interventions for neuro-musculoskeletal disorders.

bioengineering↗

bioRxiv2019

Algorithmic differentiation improves the computational efficiency of OpenSim-based optimal control simulations of movement

Algorithmic differentiation (AD) is an alternative to finite differences (FD) for evaluating function derivatives. The primarily aim of this study was to demonstrate the computational benefits of using AD instead of FD in OpenSim-based optimal control simulations. The secondary aim was to evaluate computational choices including different AD tools, different linear solvers, and the use of first- or second-order derivatives. First, we enabled the use of AD in OpenSim through a custom source code transformation tool and through the operator overloading tool ADOL-C. Second, we developed an interface between OpenSim and CasADi to perform optimal control simulations. Third, we evaluated computational choices through simulations of perturbed balance, two-dimensional predictive simulations of walking, and three-dimensional tracking simulations of walking. We performed all simulations using direct collocation and implicit differential equations. Using AD through our custom tool was between 1.8 {+/-} 0.1 and 17.8 {+/-} 4.9 times faster than using FD, and between 3.6 {+/-} 0.3 and 12.3 {+/-} 1.3 times faster than using AD through ADOL-C. The linear solver efficiency was problem-dependent and no solver was consistently more efficient. Using second-order derivatives was more efficient for balance simulations but less efficient for walking simulations. The walking simulations were physiologically realistic. These results highlight how the use of AD drastically decreases computational time of optimal control simulations as compared to more common FD. Overall, combining AD with direct collocation and implicit differential equations decreases the computational burden of optimal control simulations, which will facilitate their use for biomechanical applications.

bioengineering↗