No abstract

Spatiotemporalgait analysis can provide quantitative information to assess treatment outcomes in stroke survivors. Therefore, clinicians need a portable, easy-to-use and low-cost tool, which accurately and reliably measures spatiotemporal gait parameters. This study examined the concurrent validity and reproducibility of the Gait Up© gait analysis package for spatiotemporal gait analysis in subacute stroke survivors. Twenty-five subacute stroke survivors participated in 2 walking tests. Spatiotemporal gait parameters were synchronously measured by 2 foot-worn inertial sensors (Physilog®) and three-dimensional motion capturing (Vicon). Intraclass correlation coefficients, standard errors of measurement, smallest detectable changes, limits of agreement and Bland-Altman plots were calculated for the paretic and nonparetic side. After removing a consistent outlier (i.e. data of the paretic side of subject 36 who dragged his foot), agreement between both devices was good to excellent for paretic and nonparetic gait cycle time, cadence, stride length, stride velocity and double support; and moderate for paretic and non-paretic stance and swing. Bland-Altman plots supported these findings. Testretest reliability was good to excellent for most parameters, except paretic stance and swing. In conclusion, the Gait Up© gait analysis package is a valid and reliable tool to measure paretic and nonparetic gait cycle time, cadence, stride length and stride velocity in subacute patients with stroke, who don't exhibit severe dragging of the paretic foot. However, the algorithm should be improved for the analysis of paretic stance and swing phase.

Muscle weakness is a common clinical symptom in children with spastic cerebral palsy (SCP). It is caused by impaired neural ability and altered intrinsic capacity of the muscles. To define the contribution of decreased muscle size to muscle weakness, two cohorts were recruited in this cross-sectional investigation: 53 children with SCP [median age, 8.2 (IQR, 4.1) years, 19/34 uni/bilateral] and 31 children with a typical development (TD) [median age, 9.7 (IQR, 2.9) years]. Muscle volume (MV) and muscle belly length for m. rectus femoris, semitendinosus, gastrocnemius medialis, and tibialis anterior were defined from three-dimensional freehand ultrasound acquisitions. A fixed dynamometer was used to assess maximal voluntary isometric contractions for knee extension, knee flexion, plantar flexion, and dorsiflexion from which maximal joint torque (MJT) was calculated. Selective motor control (SMC) was assessed on a 5-point scale for the children with SCP. First, the anthropometrics, strength, and muscle size parameters were compared between the cohorts. Significant differences for all muscle size and strength parameters were found (p ≤ 0.003), except for joint torque per MV for the plantar flexors. Secondly, the associations of anthropometrics, muscle size, gross motor function classification system (GMFCS) level, and SMC with MJT were investigated using univariate and stepwise multiple linear regressions. The associations of MJT with growth-related parameters like age, weight, and height appeared strongest in the TD cohort, whereas for the SCP cohort, these associations were accompanied by associations with SMC and GMFCS. The stepwise regression models resulted in ranges of explained variance in MJT from 29.3 to 66.3% in the TD cohort and from 16.8 to 60.1% in the SCP cohort. Finally, the MJT deficit observed in the SCP cohort was further investigated using the TD regression equations to estimate norm MJT based on height and potential MJT based on MV. From the total MJT deficit, 22.6–57.3% could be explained by deficits in MV. This investigation confirmed the disproportional decrease in muscle size and muscle strength around the knee and ankle joint in children with SCP, but also highlighted the large variability in the contribution of muscle size to muscle weakness.

A shared design goal for most robotic lower limb exoskeletons is to reduce the metabolic cost of locomotion for the user. Despite this, only a limited amount of devices was able to actually reduce user metabolic consumption. Preservation of the natural motion kinematics was defined as an important requirement for a device to be metabolically beneficial. This requires the inclusion of all human degrees of freedom (DOF) in a design, as well as perfect alignment of the rotation axes. As perfect alignment is impossible, compensation for misalignment effects should be provided. A misalignment compensation mechanism for a 3-DOF system is presented in this paper. It is validated by the implementation in a bilateral hip exoskeleton, resulting in a compact and lightweight device that can be donned fast and autonomously, with a minimum of required adaptations. Extensive testing of the prototype has shown that hip range of motion of the user is maintained while wearing the device and this for all three hip DOFs. This allowed the users to maintain their natural motion patterns when they are walking with the novel hip exoskeleton.