A Multiple Degree of Freedom Lower Extremity Isometric Device to Simultaneously Quantify Hip, Knee, and Ankle Torques

Abstract

Characterization of the joint torque coupling strategies used in the lower extremity to generate maximal and submaximal levels of torque at either the hip, knee or ankle is lacking. Currently, there are no available isometric devices that quantify all concurrent joint torques in the hip, knee and ankle of a single leg during maximum voluntary torque generation. Thus, joint-torque coupling strategies in the hip, knee and concurrent torques at ankle and/or coupling patterns at the hip and knee driven by the ankle have yet to be quantified. This manuscript describes the design, implementation and validation of a multiple degree of freedom, lower extremity isometric device (the MultiLEIT) that accurately quantifies simultaneous torques at the hip, knee and ankle. The system was mechanically validated and then implemented with two healthy control individuals and two post-stroke individuals to test usability and patient acceptance. Data indicated different joint torque coupling strategies used by both healthy individuals. In contrast, data showed the same torque coupling patterns in both post-stroke individuals, comparable to those described in the clinic. Successful implementation of the MultiLEIT can contribute to the understanding of the underlying mechanisms responsible for abnormal movement patterns and aid in the design of therapeutic interventions.

Neural Constraints Affect the Ability to Generate Hip Abduction Torques When Combined With Hip Extension or Ankle Plantarflexion in Chronic Hemiparetic Stroke

“…Participants were fitted into the MultiLEIT [Figure 1 ; see ( 27 )]. Joint angles for the tested leg were set to 20° hip and knee flexion, 0° ankle flexion and 10° hip abduction.…”

“…Force and torque data were smoothed using a 250 ms moving average window. Joint torques were calculated using Jacobian transformation matrices applied to the smoothed force and torque data measured by the MultiLEIT ( 27 ). The hip abduction torque achieved at each level was defined as the maximum torque value obtained while the hip flexion/extension or the ankle plantarflexion was within 10% of the target submaximal torque.…”

“…Similarly, in the lower extremity, previous studies have shown that independent joint control might be affected when generating maximal and submaximal voluntary torques in either hip extension or ankle plantarflexion ( 25 ). Generation of maximal ankle plantarflexion and maximal hip extension in individuals post-stroke leads to coupled extension/adduction torques across the hip, knee and ankle joints ( 25 – 27 ). These results are in agreement with what is referred clinically as the extensor synergy: coupling of hip extension and hip adduction with knee extension and ankle plantarflexion ( 28 , 29 ).…”

Design and Voluntary Motion Intention Estimation of a Novel Wearable Full-Body Flexible Exoskeleton Robot

“…The lower limb of human is generally believed to have seven degrees of freedom [20]: hip adduction, abduction, external …”

A Method to Quantify Multi-Degree-of-Freedom Lower Limb Isometric Joint Torques in Children with Hemiplegia

“…The use of multi-DOF measurement tools does offer a better approach. This paper will focus on the use of a multijoint lower extremity isometric torque (MultiLEIT) device [9] to quantify weakness and abnormal joint torque coupling patterns at the hip in children with hemiplegia. Indeed, prior studies have used this device to quantify extensor coupling patterns in the paretic lower limb of adults following hemiparetic stroke [4]- [5].…”