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Yes / Background Disruptions to the progress of the centre-of-pressure trajectory beneath prosthetic feet have been reported previously. These disruptions reflect how body weight is transferred over the prosthetic limb and are governed by the compliance of the prosthetic foot device and its ability to simulate ankle function. This study investigated whether using an articulating hydraulic ankle attachment attenuates centre-of-pressure trajectory fluctuations under the prosthetic foot compared to a fixed attachment. Methods Twenty active unilateral trans-tibial amputees completed walking trials at their freely-selected, comfortable walking speed using both their habitual foot with either a rigid or elastic articulating attachment and a foot with a hydraulic ankle attachment. Centre-of-pressure displacement and velocity fluctuations beneath the prosthetic foot, prosthetic shank angular velocity during stance, and walking speed were compared between foot conditions. Findings Use of the hydraulic device eliminated or reduced the magnitude of posteriorly directed centre-of-pressure displacements, reduced centre-of-pressure velocity variability across single-support, increased mean forward angular velocity of the shank during early stance, and increased freely chosen comfortable walking speed (P ≤ 0.002). Interpretation The attenuation of centre-of-pressure trajectory fluctuations when using the hydraulic device indicated bodyweight was transferred onto the prosthetic limb in a smoother, less faltering manner which allowed the centre of mass to translate more quickly over the foot.

The diploma thesis "Vliv palce nohy na stabilitu stoje a chůze" is focused on the function of hallux at stance and through the gait cycle and particularly to halluxes influence on stability of the stated motor stereotypes. The theoretical part summarizes the knowledge gained through literature research on anatomy and kinesiology of hallux. It also contains analysis of gait cycle and muscle coordination through it with emphasis upon activity of foot and function of hallux muscles. The practical part attempts to objectivize changes in stability and changes of loading of foot with instrumental examination. Force plate Balance Master® and GaitPlatform FDM were used for the measurements. On the force plate the parametres of movement of the centre of mass (COM, COG) and maintenance of stability while standing were compared. GaitPlatform® was used for measurement of ground reaction forces while standing and walking. Powered by TCPDF (www.tcpdf.org)

Knee function after more than 20 years post injury is rarely described and none of the few follow-up studies have evaluated functional performance tasks. This thesis investigated self-reported knee function, physical activity level, physical capacity and movement pattern in the long-term perspective (on average 23 years) in persons who had suffered a unilateral ACL injury, treated either with physiotherapy in combination with surgery (ACLR, n=33) or physiotherapy alone (ACLPT, n=37) and compared to age-and-gender matched controls (n=33).  This thesis shows that regardless of treatment, there are significant negative long-term consequences on self-reported knee function and physical activity more than 20 years after injury. In comparison to the controls, the ACL-groups (ACLR and ACLPT) had lower knee function as measured by the Lysholm score and the Knee injury and Osteoarthritis Outcome Score (KOOS). The persons with an ACL injury also had a lower knee-specific physical activity level (Tegner activity scale), while no differences were seen in general physical activity level (International Physical Activity Questionnaire, IPAQ) compared to healthy controls. Regarding physical capacity, both ACL groups showed inferior jump capacity in the injured leg compared to the non-injured leg. However, compared to controls the ACL-injured had a relatively good jump performance. Knee extension peak torque, concentric and eccentric, was also lower for the injured leg compared to the non-injured leg for both ACLR and ACLPT. In addition, the ACLPT group showed reduced eccentric knee flexion torque of the injured leg. The non-injured leg, on the other hand, showed almost equal jump capacity and strength as controls. Balance in single-limb stance (30s) was inferior in persons who had an ACL injury. This was true for both the injured and non-injured leg and regardless of treatment. Movement pattern during the one-leg hop was analysed by a set of kinematic variables consisting of knee angles (flexion, abduction, rotation) and Centre of Mass (CoM) placement in relation to the knee and ankle joints. Both ACLR and ACLPT displayed movement pattern asymmetries between injured and non-injured legs. In comparison to controls, the ACLR group had a similar movement pattern with the exception of larger external knee rotation at Initial contact and less maximum internal rotation during the Landing. ACLPT showed several differences compared to controls both regarding knee angles and CoM placement. The ACL-injured persons with no-or-low knee osteoarthritis (OA) had better knee function as reflected by higher scores on Lysholm and KOOS subscale ‘symptom’ compared to those with moderate-to-high OA. The degree of OA had no influence on reported physical activity level, jump capacity, peak torque or the kinematic variables.  In conclusion, this thesis indicates that persons with a unilateral ACL injury, regardless of treatment, have some negative long-term consequences e.g. self-reported knee function, knee-specific activity level, strength and balance deficits, when compared to age-and-gender matched controls. The results, however, also indicate that the ACL-injured can manage reasonably well in some jumps and general activity level but have an inferior performance in more knee-demanding tasks. The ACLR group had similar movement pattern with the exception of knee rotation, indicating that a reconstruction may restore the knee biomechanics to some extent. The ACLPT group on the other hand, seem to use compensatory movement strategies showing several differences compared to controls.

Background: Subconcussion, a mild traumatic brain injury, is best defined and identified by a lack of observable symptoms after axonal injury from minor head impacts. Subconcussive impacts are believed to accumulate with increased exposure over time, and are likely prodromal in the manifestation of a full-blown concussion. As evidenced by changes to changes in cerebral neurochemistry and structure, it is apparent that although individuals who have accumulated subconcussion may present as asymptomatic for motor and/or cognitive impairment using current clinical assessment tools, there is indication of long-term neurological damage which is presently going unrecognized. Objective: For the reasons stated above, a more sensitive and objective assessment tool is required to assess and recognize prodromal concussion manifestation in at risk populations with the intention of preventing further chronic sequelae. Design: Multiple baseline, time-series with repeated measures. Methods: Balance and bilateral reflex variability was assessed at pre-season and at post-season. Results: The current study identified significant changes to static balance postures (taken from the Balance Error Scoring System) through an objective postural assessment of centre of pressure (COP) and Area of Ellipse (AoE) calculations using a low-cost balance board and basic software interface after a season of accumulated subconcussion in female varsity rugby athletes. Specifically, double stance on the floor worsened by 31% in COPAP (p=.025) and by 26% in COPT (p=.038) and tandem stance on an unstable foam surface worsened by 180% in COPML (p=.014), 175% in COPAP (p=.025) and 141% in COPT (p=.005) between pre-and post-season. Our results indicate that these outcome measures are sensitive and can discriminate underlying balance deficits associated with accumulated subconcussive impacts. An objective measurement of spinal cord excitability through bilateral fluctuations of the Hoffman (H-) reflex in the tibial nerve found significantly elevated pre-season Cross Covariance (CCV) values which were 3x higher than those of a neurologically intact control population, suggesting prior neurological damage in study participants. Conclusion: The current study provides a platform for future research investigating bilateral fluctuation in spinal cord excitability after accumulated subconcussion and confirms balance decrements related to subconcussion can be identified through sensitive and specific measurement tools. / Graduate

Title: Use of Imoove to influence golf players' postural stability Objectives: The aim of this study was to compare the influence of the training on the Imoove platform on the static and the dynamic postural stability in golf players. Methods: Twelve probands, golf players, participated in this study. They were divided into the experimental and into the control group. The experimental group underwent a 4-week training in a total amount of 8 exercise units. The intervention proceeded 2 times a week and lasted 30 minutes. The control group proceeded no intervetion. The measurement of the postural stability on the stabilografic platform Footscan and the mechanic platform Imoove was done at the beginning and at the end of the experiment. The results were compared in both groups. Results: The positive influence of the training on Imoove on the dynamic postural stability was confirmed in the golf players. Statistcally significant improvement of the dynamic postural stability was observed at the end of the experiment in the experimental group. There was also observed statistcally significant improvement of the dynamic postural stability in the test with hidden feedback in comparison with the control group. Values of the static postural stability in experimental group significantly worsened at the end of...

Parkinson's disease (PD) is a neurological condition that can lead to changes to gait and postural stability of people with this condition. Tai Chi (TC) has been recommended for the management of PD by improving muscle strength, balance, and coordination. However, biomechanics research in TC for PD is lacking. This thesis investigated the effects of a biomechanical-based TC intervention program for people in the early-stage of PD by realizing three specific research objectives: 1) to develop a biomechanical-based TC intervention program for PD; 2) to examine the effects of a 12-week TC intervention on gait and postural stability in people with PD, by pre-test and post-test biomechanical analysis of obstacle crossing; 3) to explore the neuromuscular effects of TC intervention on gait and postural stability by analyzing the electromyography (EMG) activity of the lower limb muscles during obstacle crossing. Seven typical TC movements were selected, including Starting Form, Hero Touch Sky, Push Hand Back, Brush Knee and Twist Step, Repulse Monkey, Wave-hand in Cloud, and Lateral Forward Step to develop the TC intervention program. The joint angles, joint moment, and EMG signals of lower limbs muscles were analyzed during performance of the selected TC movements by an experienced TC master aged 38 years. Results showed that the selected TC movements are characterized by multidirectional movements, greater joint movement angles of the lower limb, and more active muscle activity than walking. The TC intervention program was formed based on the biomechanics analysis of the seven TC movements. The program consisted of 5-10 min warm up, 40 minutes of core activities, and 5 min cool down. To examine the effects of a biomechanical-based TC intervention program on gait and postural stability and to explore the neuromuscular effects of TC intervention on the lower limb muscles in people with PD, fifteen individuals in the early stage of PD (n = 15, Hoehn and Yahr stages 1 to 2; age 72.0 ± 6.9) participated in a 12-week online TC intervention, and 15 age- and sex-matched healthy participants (n = 15) served as control. The 3D motion data of the lower limb and EMG signals from the rectus femoris, adductor longus, tibialis anterior, semitendinosus, gluteus medius, tensor fasciae latae, and medial and lateral gastrocnemius muscles were collected during obstacle crossing from both groups using Vicon motion analysis system before intervention in both groups and after TC intervention in the TC group. Obstacle crossing was used to challenge the participants' gait and postural stability. Gait was assessed by measuring the temporospatial parameters such as crossing stride length, crossing step length, and crossing speed. Postural stability was assessed by measuring toe and clearance distance, pre- and post-horizontal distance, displacement and velocity of center of mass (COM), and COM-center of pressure (COP) separation. To examine the neuromuscular activity of the lower limbs following TC training, the ratio of the peak EMG, the integrated EMG (iEMG), and the ratio of the peak EMG and iEMG antagonistic pairs of the leading and trailing limb were examined during obstacle crossing and walking. In addition, the timed up-and-go test (TUG) and single-leg stance with eyes open and closed were tested. VICON Nexus, custom MATLAB scripts, and SPSS software (version 20) were used to analyze the data. Analysis of the PD participants' obstacle crossing performance revealed that they had significantly slower gait speed, smaller hip flexion angles, and larger knee adduction angles of the trailing limb, significantly larger mediolateral (ML) COM displacement and COM-COP separation distance, and significantly higher peak EMG ratios of the adductor longus, gluteus medius, and tensor fasciae latae (p < 0.05) than the healthy participants. Following the 12-week TC intervention, the PD participants had significantly increased crossing stride length, significantly decreased ML COM-COP separation (p < 0.05) and significantly increased AP COM displacement (p < 0.05), and increased EMG activity of the tibialis anterior in the leading and trailing limbs during obstacle crossing, whereas the activity of the gluteus medius and adductor longus in the leading limb decreased (p < 0.05). Moreover, the significant differences in the EMG of the gluteus medius and tensor fasciae latae muscles between PD and healthy participants found in pre-test were no longer present. After the TC intervention, the PD participants significantly improved their performance on the TUG test (p = 0.002). Therefore, people with early-stage PD presented changed gait and postural stability as well as changed neuromuscular activity of the lower limb. The 12-week online biomechanical-based TC intervention improved their gait and postural stability, particularly dynamic postural stability as measured by the COM-COP separation in people with early-stage PD. Compared to walking, performing the TC movements involved larger changes in the lower limb angles, range of motion, and higher muscle activity, particularly in the hip abductors and adductors. These characteristics of the TC movements could provide training to strengthen the muscles and improve the range of motion of the lower limbs. The gait and postural stability improvements following TC intervention are consistent with the neuromuscular activity changes in gluteus medius, tensor fasciae latae, and adductor longus muscles, indicating the mechanisms of TC training. The 12-week online biomechanical-based TC intervention program helped to decrease the ML COM-COP separation distance and could be used for the management of PD in the early stages of this condition.

The paper overviews the modes of vibration of the principal component parts of a brake and their contribution to system instability during noise generation. It is shown that both in-plane and out-of-plane vibration is present and that both can be related to the vibration of the pad. It is further shown that the pad and its region often provide a solution or 'fix' towards noise prevention and it is this area that forms the focus of this investigation. The collective evidence, proposals and associated theory are applied to real brake case studies when it is demonstrated that disc/pad interface 'spragging' may be the source of brake noise. Measurements of the position of the dynamic centre of pressure (CoP) support the theoretical predictions that a leading CoP induces brake noise. Design proposals are suggested that may be applied early in the design phase as a means to reduce the propensity of a brake to generate noise.

No / Unilateral lower-limb amputees lead with their intact limb when stepping up and with their prosthesis when stepping down; the gait initiation process for the different stepping directions has not previously been investigated. Ten unilateral amputees (5 transfemoral and 5 transtibial) and 8 able-bodied controls performed single steps up and single steps down to a new level (73 and 219 mm). Duration, a-p and m-l centre of mass and centre of pressure peak displacements and centre of mass peak velocity of the anticipatory postural adjustment and step execution phase were evaluated for each stepping direction by analysing data collected using a Vicon 3D motion analysis system. There were significant differences (in the phase duration, peak a-p and m-l centre of pressure displacement and peak a-p and m-l centre of mass velocity at heel-off and at foot-contact) between both amputee sub-groups and controls (P<0.05), but not between amputee sub-groups. These group differences were mainly a result of amputees adopting a different gait initiation strategy for each stepping direction. Findings indicate the gait initiation process utilised by lower-limb amputees was dependent on the direction of stepping and more particularly by which limb the amputee led with; this suggests that the balance and postural control of gait initiation is not governed by a fixed motor program, and thus that becoming an amputee will require time and training to develop alternative neuromuscular control and coordination strategies. These findings should be considered when developing training/rehabilitation programs.

Optimal interaction between vision and other somatosensory systems guaranties the control of human body segment stability and change in position. The lack of visual information causes changes in equilibrium, regulation of body segment position and in response to surrounding stimuli. The objective of the study: to carry out the research on the influence of the degree of visual impairment on equilibrium and simple and psychomotor reactions, and to establish the possible manifestation of compensatory reactions of vestibular and proprioception sensory systems when vision disorders are being faced. To investigate the influence of the degree of visual impairment on equilibrium and simple and psychomotor reactions, the sighted subjects, legally blind and totally blind subjects voluntarily participated in the study. A static posturography (or stabilography) method has been used for the equilibrium testing. A force plate and computerized equipment for analysis of the signals was applied for posturography. Centre of pressure coordinates have been started to be registered since the moment when the subject in bare feet stands on the force plate in the position required. Posturogram registration in every position of standing lasted 60 s. To investigate a simple reaction, we have employed an electromyoreflexometer, which consists of the equipment emitting light or sound signals, a response device and a unit for the data registration. The testing has been conducted during two parts when a... [to full text]