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Background: Freezing of gait (FoG) is an episodic failure of gait exposing people with Parkinson's disease (PD) to a high risk of falling. Despite growing evidence of the interconnection between impaired trunk control and FoG, a detailed description of spinal kinematics during walking is still lacking in this population., Research Question: Do spinal alterations impact gait performance in individuals with PD and FoG?, Methods: We analyzed kinematic data of 47 PD participants suffering (PD-FOG, N = 24) or not suffering from FoG (PD-NFOG, N = 23) and 15 healthy controls (HCO) during quiet standing and unperturbed walking. We estimated the main spinal variables (i.e., spinal length, lordosis and kyphosis angles, trunk inclination), the pelvis angles, and the shoulder-pelvis angles during gait and standing. We studied differences across conditions and groups and the relationships between postural and gait parameters using linear regression methods., Results: During standing and walking, both PD groups showed increased trunk inclination and decreased lordosis angle with respect to HCO, as well as a decreased range in variation of kyphosis angle, pelvic obliquity, and shoulder-pelvis angles. Only PD-FOG participants showed reduced range of lordosis angle and spinal length compared to HCO. PD-FOG individuals were also not able to straighten their spine during walking compared to standing. Stride length and velocity were decreased in both patient groups compared to HCO, while swing duration was reduced only in the PD-FOG group. In individuals with FoG, trunk inclination and lordosis angle showed moderate but significant positive correlations with all gait alterations., Significance: Spine alterations impacted gait performance in individuals with PD suffering from FoG. Excessive trunk inclination and poor mastering of the lordosis spinal region may create an unfavourable postural precondition for forward walking. Physical therapy should target combined spinal and stepping alterations in these individuals., Competing Interests: Declaration of Competing Interest None., (Copyright © 2023 The Authors. Published by Elsevier B.V. All rights reserved.)

Background: Power and work at the ankle joint during gait are usually computed considering the foot as a rigid body [1-6] (Ankle Joint method, AJ). The foot is instead a deformable structure and can absorb and produce work by pronation/supination, foot arch deformation and other intrinsic movements. A different approach, named "the Distal Shank method (DS)" [7-12] considers all these aspects without increasing the complexity of the protocol, and thus it seems promising for clinical applications [12]., Research Questions: a) To characterize the differences in power and work computed using the two mentioned methods for a relatively large number of subjects walking at different velocities, barefoot and with different shoes; b) To assess the practical feasibility of the DS method for clinical applications., Materials and Methods: Eighteen healthy subjects were evaluated while walking barefoot at slow, natural and fast velocity. Shod walking was analysed at natural velocity. Four subjects were also analysed while walking in high-heel shoes. The power at the ankle joint was computed with both the AJ and the DS methods. We then compared the obtained results., Results: The DS method showed a consistent negative peak of power absorption during the load acceptance phase, barely visible with the AJ method. The maximum power production calculated with the DS method was significantly lower. The work at the end of the stride cycle was lower with the DS method, and in most conditions even negative, thus indicating higher energy dissipation., Significance: We confirmed on a large cohort of healthy subjects and in different walking conditions that neglecting foot deformations during gait leads to underestimate power absorption and overestimate power production. The DS method does not require a complex gait analysis protocol, nor additional time for the analysis, and can provide information of clinical interest, related to foot mechanical alterations., (Copyright © 2019 Elsevier B.V. All rights reserved.)

The importance of peripheral visual information during stair climbing and how peripheral visual information is weighted as a function of step number during step climbing is unclear. Previous authors postulated that the knowledge of predictable characteristics of the steps may decrease reliance on foveal vision and transfer the online visual guidance of stair climbing to peripheral vision. Hence the aim of this study was to investigate if and how the occlusion of the lower peripheral visual field influenced stair climbing and if peripheral visual information was weighted differently between steps. Ten young adult male participants ascended a 5-step staircase under 2 visual conditions: full vision (FV) and lower visual occlusion (LO). Kinematic data (100Hz) were collected. The effect of Vision and Step condition on vertical forefoot clearance was examined with a Repeated Measures 2-way ANOVA. Tukey's HSD test was used for post-hoc comparisons. A significant interaction Vision x Step and main effect of Step were found (p<=0.04): vertical forefoot clearance was greater in LO compared to FV condition only on the 1st and the 2nd steps (p<0.013) and on the last step compared to the other steps (p<0.01). These findings suggest that online peripheral visual information is more relevant when negotiating the first two steps, rather than the end of a staircase and that the steps subsequent the first few ones may require different information likely based on proprioception or working memory of the step height., (Copyright © 2016 Elsevier B.V. All rights reserved.)

The mechanical effect of hamstrings and quadriceps contractions on hip and knee joint motion was investigated using a dynamic model of the musculoskeletal system. The model consisted of 13 anatomically linked segments. The geometry of bones, joints, and muscle attachments was derived from magnetic resonance imaging of a healthy adult. The knee joint was represented by a crossing bars linkage to simulate cruciate ligament function, and muscles were represented by spring actuators. The effects of hamstring and quadriceps contractions, in various combinations, were tested on different configurations of hip and knee joint position in the absence of gravity. In the standing posture, with the foot free to move and the pelvis fixed in space, the effect of semimembranosus (SM) contraction was hip and knee flexion. If the foot was fixed to the ground, SM contraction produced hip extension and knee flexion. The addition of quadriceps contraction reduced or abolished the knee flexion and enhanced hip extension. In all other simulations, SM alone produced knee flexion and hip extension and the combination of SM with vastus (VA) and rectus femoris (RF) contractions resulted in knee extension and enhanced hip extension. Our findings suggest that co-contraction of quadriceps and hamstrings may be a strategy to increase the hip extension function of the hamstrings., (Copyright 2009 Elsevier B.V. All rights reserved.)

Data collection and reduction procedures, coherently structured in protocols, are necessary in gait analysis to make kinematic and kinetic measurements clinically comprehensible. The current protocols differ considerably for the marker-set and for the biomechanical model implemented. Nevertheless, conventional gait variables are compared without full awareness of these differences. A comparison was made of five worldwide representative protocols by analysing kinematics and kinetics of the trunk, pelvis and lower limbs exactly over the same gait cycles. A single comprehensive arrangement of markers was defined by merging the corresponding five marker-sets. This resulted in 60 markers to be positioned either on the skin or on wands, and in 16 anatomical landmark calibrations to be performed with an instrumented pointer. Two healthy subjects and one patient who had a special two degrees of freedom knee prosthesis implanted were analysed. Data from up-right posture and at least three gait repetitions were collected. Five corresponding experts participated in the data collection and analysed independently the data according to their own procedures. All five protocols showed good intra-protocol repeatability. Joint flexion/extension showed good correlations and a small bias among protocols. Out-of-sagittal plane rotations revealed worse correlations, and in particular knee abduction/adduction had opposite trends. Joint moments compared well, despite the very different methods implemented. The abduction/adduction at the prosthetic knee, which was fully restrained, revealed an erroneous rotation as large as 30 degrees in one protocol. Higher correlations were observed between the protocols with similar biomechanical models, whereas little influence seems to be ascribed to the marker-set.

Modelling the effect of soleus and gastrocnemius contractions against the floor resistance in a forward dynamics simulation revealed that hip flexion, internal rotation and adduction together with external pelvic rotation could be attributed to a direct, but distant effect of triceps surae contraction. Knee flexion smoothed out the effect. To validate this clinically relevant biomechanical observation, ankle plantar flexion was correlated with hip and pelvic rotation retrospectively in children with spastic cerebral palsy. In 49 children with spastic hemiplegia, plantar flexion showed a significant correlation with increased pelvic retraction and hip internal rotation. In contrast, in 47 children with spastic diplegia no significant effect of the triceps surae on hip and pelvis kinematics was found. Bilateral hip and knee flexion in diplegia appeared to prevent the proximal effect of the triceps surae seen in the hemiplegics. In diplegia triceps surae overactivity did not appear to be a significant cause of internal rotation gait.

We used kinematic, kinetic and EMG analysis to compare the spontaneous heel-contact gait patterns of 13 children classified as habitual toe walkers (HTWs) and age-matched controls. In the HTWs, the incidence of spontaneous heel-contact strides during a single recording session ranged from 15% to 92%, with no correlation with age, passive ankle joint excursion, walking speed and trial order. Hallmarks of the heel-contact strides were premature heel-rise, reversal of the second rocker, relative shortening of the loading response and anticipation and enhancement of the electromyographic (EMG) activity normally observed in the triceps surae (TS) during the first half of the stance phase. This variant of the locomotor program is different from the walking patterns observed in normally developing toddlers and children with cerebral palsy (CP). It does not necessarily reflect a functional adaptation to changes in the rheological properties of the muscle-tendon complex.

Spatial and temporal parameters of gait have clinical relevance in the assessment of motor pathologies, particularly in orthopaedics. A new gait analysis system is proposed which consists of (a) an ambulatory device (Physilog) including a set of miniature gyroscopes and a portable datalogger, and (b) an algorithm for gait analysis. The aim of this study was the validation of this system, for accuracy and clinical applicability. Eleven patients with coxarthrosis, eight patients with total hip arthroplasty and nine control subjects were studied using this portable system and also a reference motion analyzer and force plate. The small differences in the stance period (19 +/- ms), stride length and velocity (0.4 +/- 9.6 cm and 2.5 +/- 8.3 cm/s, respectively), as well as thigh and shank rotations (2.4 +/- 4.3 degrees and 0.3 +/- 3.3 degrees, respectively), confirmed good agreement of the proposed system with the reference system. In addition, nearly the same accuracy was obtained for all three groups. Gait analysis based on Physilog was also in agreement with their Harris Hip Scores (HHS): the subjects with lower scores had a greater limp, a slower walking speed and a shorter stride. This ambulatory gait analysis system provides an easy, reproducible and objective method of quantifying changes in gait after joint replacement surgery for coxarthrosis., (Copyright 2003 Elsevier B.V.)

The aim of this study was to investigate the biomechanics and motor co-ordination in humans during stair climbing at different inclinations. Ten normal subjects ascended and descended a five-step staircase at three different inclinations (24 degrees, 30 degrees, 42 degrees ). Three steps were instrumented with force sensors and provided 6 dof ground reactions. Kinematics was analysed by a camera-based optoelectronic system. An inverse dynamics approach was applied to compute joint moments and powers. The different kinematic and kinetic patterns of stair ascent and descent were analysed and compared to level walking patterns. Temporal gait cycle parameters and ground reactions were not significantly affected by staircase inclination. Joint angles and moments showed a relatively low but significant dependency on the inclination. A large influence was observed in joint powers. This can be related to the varying amount of potential energy that has to be produced (during ascent) or absorbed (during descent) by the muscles. The kinematics and kinetics of staircase walking differ considerably from level walking. Interestingly, no definite signs could be found indicating that there is an adaptation or shift in the motor patterns when moving from level to stair walking. This can be clearly seen in the foot placement: compared to level walking, the forefoot strikes the ground first--independent from climbing direction and inclination. This and further findings suggest that there is a certain inclination angle or angular range where subjects do switch between a level walking and a stair walking gait pattern.

Estimation of joint centres is required in gait analysis for kinematic and kinetic elaboration. In general, the method is based on regression equations and palpation of bone prominences. A kinematic approach can also be used at the hip joint but appears to be more demanding for the patients. The method presented here combines different independent approaches and is aimed at reducing the estimation errors caused by from skin motion artefacts and statistical variance of anthropometric data. It is based on minimising an optimisation function in which data from gait kinematics, anthropometric measurements and statistically derived morphological parameters are properly weighted. The procedure is suitable for clinical applications where the range of motion might be reduced and the patients can not perform complicated exercises. Validation has been made on ten normal subjects and ten patients with spina bifida. The results show that the reproducibility of the estimation and the congruency with the external measurements is improved with respect to both the morphologically based approach and the kinematic method. Copyright 1998 Elsevier Science B.V.