Linear parameter varying identification of ankle joint intrinsic stiffness during imposed walking movements

Tehrani, Ehsan Sobhani; Jalaleddini, Kian; Kearney, Robert E.

doi:10.1109/embc.2013.6610652

Cited by 9 publications

(5 citation statements)

References 14 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Figure 10C demonstrates that the ankle static stiffness can take different values for the same ankle angle depending on the immediate history of the movement. This demonstrates a true TV behavior in the joint neuromuscular properties, and not just a static-nonlinear dependency on joint position, as has been previously assumed (Sobhani Tehrani et al, 2013 ; Jalaleddini et al, 2015 ).…”

Section: Discussionsupporting

confidence: 75%

“…These type of models cannot provide any information regarding the modulation of reflex mechanisms and likely overestimate the contribution of intrinsic mechanisms to the overall dynamic joint stiffness. We have introduced methods to estimate intrinsic and stretch reflex mechanisms using the parallel-cascade model structure during TV conditions; however, these methods require very large data sets for parameter estimation, which severely limits their application (Giesbrecht et al, 2006 ; Ludvig et al, 2011 ; Guarin and Kearney, 2012 , 2015b ); or make the strong assumption that there is a static-nonlinear relation between the parallel-cascade model parameters and joint position or torque (Sobhani Tehrani et al, 2013 ; Jalaleddini et al, 2015 ). Despite their limitations, these studies have shown that the interpolation of parameter values obtained from stationary experiments does not describe dynamic joint stiffness during TV conditions.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Estimation of Time-Varying, Intrinsic and Reflex Dynamic Joint Stiffness during Movement. Application to the Ankle Joint

Guarín

Kearney

2017

Front. Comput. Neurosci.

Self Cite

View full text Add to dashboard Cite

Dynamic joint stiffness determines the relation between joint position and torque, and plays a vital role in the control of posture and movement. Dynamic joint stiffness can be quantified during quasi-stationary conditions using disturbance experiments, where small position perturbations are applied to the joint and the torque response is recorded. Dynamic joint stiffness is composed of intrinsic and reflex mechanisms that act and change together, so that nonlinear, mathematical models and specialized system identification techniques are necessary to estimate their relative contributions to overall joint stiffness. Quasi-stationary experiments have demonstrated that dynamic joint stiffness is heavily modulated by joint position and voluntary torque. Consequently, during movement, when joint position and torque change rapidly, dynamic joint stiffness will be Time-Varying (TV). This paper introduces a new method to quantify the TV intrinsic and reflex components of dynamic joint stiffness during movement. The algorithm combines ensemble and deterministic approaches for estimation of TV systems; and uses a TV, parallel-cascade, nonlinear system identification technique to separate overall dynamic joint stiffness into intrinsic and reflex components from position and torque records. Simulation studies of a stiffness model, whose parameters varied with time as is expected during walking, demonstrated that the new algorithm accurately tracked the changes in dynamic joint stiffness using as little as 40 gait cycles. The method was also used to estimate the intrinsic and reflex dynamic ankle stiffness from an experiment with a healthy subject during which ankle movements were imposed while the subject maintained a constant muscle contraction. The method identified TV stiffness model parameters that predicted the measured torque very well, accounting for more than 95% of its variance. Moreover, both intrinsic and reflex dynamic stiffness were heavily modulated through the movement in a manner that could not be predicted from quasi-stationary experiments. The new method provides the tool needed to explore the role of dynamic stiffness in the control of movement.

show abstract

Section: Discussionsupporting

confidence: 75%

Section: Introductionmentioning

confidence: 99%

Estimation of Time-Varying, Intrinsic and Reflex Dynamic Joint Stiffness during Movement. Application to the Ankle Joint

Guarín

Kearney

2017

Front. Comput. Neurosci.

Self Cite

View full text Add to dashboard Cite

show abstract

“…Previous experimental studies have revealed that ankle joint stiffness, on average, decreases with plantarflexion until 27 • plantarflexion (Sobhani Tehrani et al, 2013;Jalaleddini et al, 2015). Thus, a reduction of muscle stiffness with muscle shortening during plantarflexion might explain our results (Davidson and Charles, 2016).…”

Section: Alternative Mechanismssupporting

confidence: 49%

Physiological tremor increases when skeletal muscle is shortened: implications for fusimotor control

Jalaleddini

Nagamori

Laine

et al. 2017

The Journal of Physiology

Self Cite

View full text Add to dashboard Cite

The involuntary force fluctuations associated with physiological (as distinct from pathological) tremor are an unavoidable component of human motor control. While the origins of physiological tremor are known to depend on muscle afferentation, it is possible that the mechanical properties of muscle-tendon systems also affect its generation, amplification and maintenance. In this paper, we investigated the dependence of physiological tremor on muscle length in healthy individuals. We measured physiological tremor during tonic, isometric plantarflexion torque at 30% of maximum at three ankle angles. The amplitude of physiological tremor increased as calf muscles shortened in contrast to the stretch reflex whose amplitude decreases as muscle shortens. We used a published closed-loop simulation model of afferented muscle to explore the mechanisms responsible for this behaviour. We demonstrate that changing muscle lengths does not suffice to explain our experimental findings. Rather, the model consistently required the modulation of γ-static fusimotor drive to produce increases in physiological tremor with muscle shortening - while successfully replicating the concomitant reduction in stretch reflex amplitude. This need to control γ-static fusimotor drive explicitly as a function of muscle length has important implications. First, it permits the amplitudes of physiological tremor and stretch reflex to be decoupled. Second, it postulates neuromechanical interactions that require length-dependent γ drive modulation to be independent from α drive to the parent muscle. Lastly, it suggests that physiological tremor can be used as a simple, non-invasive measure of the afferent mechanisms underlying healthy motor function, and their disruption in neurological conditions.

show abstract

“…The second and third-order power of joint angles (θ 2 ( t ), θ 3 ( t )) were also included in the model to account for nonlinear changes of joint biomechanics as a function of joint angle (Sobhani Tehrani et al, 2013). The main assumption of the model is that the neural component of the force is negligible, which is a fair assumption as the velocity of perturbation was low enough to avoid evoking reflex responses (Jalaleddini et al, 2016).…”

Section: Methodsmentioning

confidence: 99%

Forearm Flexor Muscles in Children with Cerebral Palsy Are Weak, Thin and Stiff

Walden

Jalaleddini

Evertsson

et al. 2017

Front. Comput. Neurosci.

Self Cite

View full text Add to dashboard Cite

Children with cerebral palsy (CP) often develop reduced passive range of motion with age. The determining factor underlying this process is believed to be progressive development of contracture in skeletal muscle that likely changes the biomechanics of the joints. Consequently, to identify the underlying mechanisms, we modeled the mechanical characteristics of the forearm flexors acting across the wrist joint. We investigated skeletal muscle strength (Grippit®) and passive stiffness and viscosity of the forearm flexors in 15 typically developing (TD) children (10 boys/5 girls, mean age 12 years, range 8–18 yrs) and nine children with CP Nine children (6 boys/3 girls, mean age 11 ± 3 years (yrs), range 7–15 yrs) using the NeuroFlexor® apparatus. The muscle stiffness we estimate and report is the instantaneous mechanical response of the tissue that is independent of reflex activity. Furthermore, we assessed cross-sectional area of the flexor carpi radialis (FCR) muscle using ultrasound. Age and body weight did not differ significantly between the two groups. Children with CP had a significantly weaker (−65%, p < 0.01) grip and had smaller cross-sectional area (−43%, p < 0.01) of the FCR muscle. Passive stiffness of the forearm muscles in children with CP was increased 2-fold (p < 0.05) whereas viscosity did not differ significantly between CP and TD children. FCR cross-sectional area correlated to age (R2 = 0.58, p < 0.01), body weight (R2 = 0.92, p < 0.0001) and grip strength (R2 = 0.82, p < 0.0001) in TD children but only to grip strength (R2 = 0.60, p < 0.05) in children with CP. We conclude that children with CP have weaker, thinner, and stiffer forearm flexors as compared to typically developing children.

show abstract

Linear parameter varying identification of ankle joint intrinsic stiffness during imposed walking movements

Cited by 9 publications

References 14 publications

Estimation of Time-Varying, Intrinsic and Reflex Dynamic Joint Stiffness during Movement. Application to the Ankle Joint

Estimation of Time-Varying, Intrinsic and Reflex Dynamic Joint Stiffness during Movement. Application to the Ankle Joint

Physiological tremor increases when skeletal muscle is shortened: implications for fusimotor control

Forearm Flexor Muscles in Children with Cerebral Palsy Are Weak, Thin and Stiff

Contact Info

Product

Resources

About