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Ankle-foot orthoses are commonly prescribed to address motor impairments in individuals with neurological disorders. Proper alignment of Ankle-foot orthoses, commonly assessed by the ground reaction force in relation to the knee joint center and the shank-to-vertical angle, is crucial for their effectiveness but is time-consuming. This study validates automated pose estimator DeepLabCut on measuring these metrics using 2D videos with force vector overlay in individuals with neurological disorders wearing ankle-foot orthoses. Thirty subjects with neurological disorders wearing ankle-foot orthoses participated. DeepLabCut's performance was compared to 3D gait analysis (Vicon). Subjects were randomly divided into three groups to train (20 subjects) and evaluate (10 subjects) DeepLabCut models. The number of subjects with untrackable points of interests in their videos was determined. The mean difference, root mean square error, intraclass correlation and repeatability coefficient between DeepLabCut and Vicon were computed for videos with trackable points of interest. Only two subjects for ground reaction force distance to the knee and four subjects for the shank-to-vertical angle had untrackable points of interest. Excellent agreement between DeepLabCut and Vicon was found for the ground reaction force distance to the knee (mean difference 0.1 mm, root mean square error 6.7 mm, intraclass correlation 0.99, repeatability coefficient 6.7 mm) and shank-to-vertical angle (mean difference 0.7°, root mean square error 1.8°, intraclass correlation 0.99, repeatability coefficient 1.6°). This study demonstrates that DeepLabCut can accurately and efficiently assess ankle-foot orthosis alignment parameters, paving the way for a simple and straightforward 2D video setup with a force-vector overlay for automated ankle-foot orthosis alignment. • First steps of automatic ankle-foot orthosis alignment were made. • Key metrics for alignment were assessed by pose estimator DeepLabCut. • Ground reaction force distance to the knee can be assessed within 1 cm accuracy. • Shank-to-vertical angle can be assessed within 2° accuracy. • Good generalizability was achieved by training the model on only 20 subjects. [ABSTRACT FROM AUTHOR]

The ability to walk safely after head and neck reconstruction with fibular free flaps in tumor surgery is a high priority for patients. In addition, surgeons and patients require objective knowledge of the functional donor-site morbidity. However, the effects of fibular free flap surgery on gait asymmetries have only been studied for step length and stance duration. This study analyses whether patients who have undergone fibular free flap reconstruction have enduring gait asymmetries compared to age-matched controls. Patients who underwent head and neck reconstruction with fibular free flaps between 2019 and 2023 were recruited, as well as age-matched controls. Participants walked on an instrumented treadmill at 3 km/h. The primary outcome measures were 22 gait asymmetry metrics. Secondary outcome measures were the associations of gait asymmetry with the length of the harvested fibula, and with the time after surgery. Nine out of 13 recruited patients completed the full assessment without holding on to the handrail on the treadmill. In addition, nine age-matched controls were enrolled. Twenty out of the 22 gait asymmetry parameters of patients were similar to healthy controls, while push-off peak force (p = 0.008) and medial impulse differed (p = 0.003). Gait asymmetry did not correlate with the length of the fibula harvested. Seven gait asymmetry parameters had a strong correlation with the time after surgery. On the long-term, fibular free flap reconstruction has only a limited effect on the asymmetry of force-related and temporal gait parameters while walking on a treadmill. • Fibular free flap harvest has very limited long-term effects on gait asymmetry. • Patients require time to improve their gait pattern after their surgery. • The size of the harvested fibula has no influence on gait asymmetry. [ABSTRACT FROM AUTHOR]

Background A slip occurs when the required friction (RCOF) to prevent slipping at the foot/floor interfaces exceeds the available friction. The RCOF is dependent upon the biomechanics features of individuals and their gait. On the other hand, the available friction depends on environmental features. Once individuals with crouch gait have their biomechanics of gait completely altered, how do they interact with a supporting surface? The aim was to quantify the RCOF in children with bilateral spastic cerebral palsy (BSCP) and crouch gait. Methods 11 children with crouch gait and 11 healthy age-matched children were instructed to walk barefoot at self-selected speed over a force platform. The RCOF curve was obtained as the ratio between the tangential forces (FT), and the vertical ground reaction force (FZ). Three points were extracted by the RCOF, FT and FZ curves at the loading response, midstance and push-off phases. Findings Children with BSCP presented higher values of RCOF in all support phase and lower gait velocity relative to the healthy controls. For BSCP group no correlation between FT and FZ were found, indicating that this group is not able to negotiate the forces during the support phase. Interpretation Children with BSCP and crouch gait are not able to negotiate the forces applied on the ground in support phase, so to avoid the fall, their strategy is to reduce the gait velocity. [ABSTRACT FROM AUTHOR]

Individuals with unilateral transfemoral amputation walk with increased levels of asymmetry, and this is associated with reduced gait efficiency, back pain and overuse of the intact limb. This study investigated the effect of walking with a unilateral absence of loading response knee flexion on the symmetry of anterior-posterior kinetics and centre of mass accelerations. A retrospective cohort study design was used, assessing three-dimensional gait data from individuals with unilateral transfemoral amputation (n = 56). The anterior-posterior gait variables analysed included; peak ground reaction forces, impulse, centre of mass acceleration, as well as rate of vertical ground reaction force increase in early stance. With respect to these variables, this study assessed the symmetry between intact and prosthetic limbs, compared intact limbs against a healthy unimpaired control group, and evaluated effect on symmetry of microprocessor controlled knee provision. Significant between-limb asymmetries were found between intact and prosthetic limbs across all variables (p < 0.0001). Intact limbs showed excessive loading when compared with control group limbs after speed normalisation across all variables (p < 0.0001). No improvement in kinetic symmetry following microprocessor controlled knee provision was found. The gait asymmetries for individuals with transfemoral amputation identified in this study suggest that more should be done by developers to address the resultant overloading of the intact limb, as this is thought to have negative long-term effects. The provision of microprocessor controlled knees did not appear to improve the asymmetries faced by individuals with transfemoral amputation, and clinicians should be aware of this when managing patient expectations. • The magnitude of kinetic asymmetries between limbs have been described. • Intact limb loading is excessive when compared with a healthy control group. • Microprocessor controlled knee provision does not improve the kinetic asymmetries. [ABSTRACT FROM AUTHOR]

Walking biomechanics are commonly affected after anterior cruciate ligament reconstruction and differ compared to uninjured controls. Manipulating task difficulty has been shown to affect the magnitude of walking impairments in those early after knee surgery but it is unclear if patients in later phases post-op are similarly affected by differing task demands. Here, we evaluated the effects of manipulating walking speed on between-limb differences in ground reaction force and knee biomechanics in those with and without anterior cruciate ligament reconstruction. We recruited 28 individuals with anterior cruciate ligament reconstruction and 20 uninjured control participants to undergo walking assessments at three speeds (self-selected, 120%, and 80% self-selected speed). Main outcomes included sagittal plane knee moments, angles, excursions, and ground reaction forces (vertical and anterior-posterior). We observed walking speed differentially impacted force and knee-outcomes in those with anterior cruciate ligament reconstruction. Between-limb differences increased at fast and decreased at slow speeds in those with anterior cruciate ligament reconstruction while uninjured participants maintained between-limb differences regardless of speed (partial η2 = 0.13–0.33, p < 0.05). Anterior cruciate ligament reconstruction patients underloaded the surgical limb relative to both the contralateral, and uninjured controls in GRFs and sagittal plane knee moments (partial η2 range = 0.13–0.25, p < 0.05). Overall, our findings highlight the persistence of walking impairments in those with anterior cruciate ligament reconstruction despite completing formal rehabilitation. Further research should consider determining if those displaying larger changes in gait asymmetries in response to fast walking also exhibit poorer strength and/or joint health outcomes. • Those with ACLR show larger ground reaction force and knee between-limb differences when walking fast. • Healthy individuals maintain gait symmetry regardless of walk speed. • After ACLR, testing a range of speeds may help detect poor walk patterns after ACLR. [ABSTRACT FROM AUTHOR]

Background Biomechanical deviations long (approx. 5 years) after anterior cruciate ligament reconstruction have not been quantified in males, despite their distinct risk profile as compared to females. These deviations can indicate altered joint loading during chronic, repetitive motions. Methods Cross-sectional study, comparing kinematic and kinetic variables between 15 male anterior cruciate ligament reconstructed patients and 15 healthy controls. During walking and running gait, measurements were taken of impact dynamics, knee and hip sagittal plane angles and moments, and knee varus angles and adduction moments. Findings Comparing affected limbs to control limbs, significantly lower maximum ( P = 0.001) and initial ( P = 0.003) loading rates were found during running, but not in walking. Hip angles were lower for affected limbs of patients compared to the control group ( P = 0.039) in walking, but not during running. Between-limb comparisons showed important differences in symmetry of the affected patients. Maximum force during running was higher in the unaffected limb ( P = 0.015), which was linked with a higher loading rate ( P = 0.008). Knee flexion angle was reduced by 2° on average for the affected limb during running ( P = 0.010), and both walking and running knee and hip moments showed differences. Knee varus angle showed a 1° difference during walking ( P < 0.001), but not during running. Knee adduction moment was significantly lower (more valgus) during both walking and running. Interpretation Male anterior cruciate ligament reconstructed patients demonstrate persistent, clinically important gait asymmetries and differences from healthy controls long after surgery in kinematics, kinetics, and impact biomechanics. [ABSTRACT FROM AUTHOR]

Background Prosthetic stiffness likely affects the walking biomechanics of toddlers and children with leg amputations, but the actual stiffness values for prostheses are not reported by manufacturers or in standardized testing procedures. Aim We measured axial (k A ) and torsional (k T ) stiffness from four brands of pediatric prosthetic feet (Trulife, Kingsley Mfg. Co., TRS Incorporated, and College Park Industries) over a range of foot sizes. Methods We applied forces and torques onto prostheses with a materials testing machine that replicated those exhibited in vivo by using the kinetics measured from four non-amputee toddlers (2–3 years) during walking. Findings Across brands, k A averaged 35.2 kN/m during heel loading, was more stiff during midfoot loading (121.8 kN/m, P < 0.001) and less stiff during forefoot loading (11.8 kN/m, P = 0.013). k A was similar across brands with no statistically significant effect of prosthetic foot size, with the exception of the TRS feet. Plantarflexion torsional stiffness (k T1 ), was not statistically different across brands. For every 1 cm increase in foot size, k T1 increased 0.16 kN·m/rad ( P < 0.001). College Park prostheses had 4.54 kN·m/rad lower dorsiflexion torsional stiffness (k T2 ) ( P < 0.001) compared to other brands. For every 1 cm increase in foot size, the k T2 applied on the foot increased 0.63 kN·m/rad. Interpretation The axial and torsional stiffness testing methods are reproducible and should be adopted by prosthetic foot manufacturers. Axial and torsional stiffness values of commercially available prosthetic feet should be publically reported to health practitioners to ensure evidence-based decisions and meet the specific needs of each patient with a leg amputation. [ABSTRACT FROM AUTHOR]

Background Individuals post hip fracture decrease force on the involved limb during sit to stand tasks, creating an asymmetry in vertical ground reaction force. Joint specific differences that underlie asymmetry of the vertical ground reaction force are unknown. The purpose of this study was to compare differences in vertical ground reaction force variables and joint kinetics at the hip and knee in participants post-hip fracture, who were recently discharged from homecare physical therapy to controls. Methods Forty-four community-dwelling older adults, 29 who had a hip fracture and 15 elderly control participant’s completed the sit to stand task on an instrumented chair with 3 force plates. T -tests were used to compare clinical tests (Berg Balance Scale, activity balance confidence and gait speed, isokinetic knee strength) and vertical ground reaction force variables. Two-way analyses of variance compared vertical ground reaction force variables and kinetics at the hip and knee between hip fracture and elderly control groups. Pearson correlation coefficients were used to determine correlations between clinical and vertical ground reaction force variables. Findings Vertical ground reaction force variables were significantly lower on the involved side for the hip fracture group compared to the uninvolved side and controls. Lower involved side hip and knee moments and power contributed to lower involved side vertical ground reaction force. Vertical ground reaction force variables and strength had moderate to high correlations with clinical measures. Interpretation Uninvolved side knee moments and powers were the largest contributors to asymmetrical vertical ground reaction force in participants post-hip fracture. The association of vertical ground reaction force variables and clinical measures of function suggesting reducing vertical ground reaction force asymmetry may contribute to higher levels of function post-hip fracture. Functional and strength training should target the involved knee to reduce vertical ground reaction force asymmetry. [ABSTRACT FROM AUTHOR]

Background Deficits in balance control are one of the most common and serious mobility challenges facing individuals with lower limb loss. Yet, dynamic postural balance control among individuals with lower limb loss remains poorly understood. Here we examined the kinematics and kinetics of dynamic balance in individuals with unilateral transtibial limb loss. Methods Five individuals with unilateral transtibial limb loss, and five age- and gender-matched controls completed a series of randomly applied multi-directional support surface translations. Whole-body metrics, e.g. peak center-of-mass displacement and net center-of-pressure displacement were compared across cohorts. Stability margin was computed as the difference between peak center-of-pressure and center-of-mass displacement. Additionally, center-of-pressure and ground reaction force magnitude and direction were compared between the prosthetic, intact, and control legs. Findings Peak center-of-mass displacement and stability margin did not differ between individuals with transtibial limb loss and controls for all perturbation directions except those loading only the prosthetic leg; in such cases the stability margin was actually larger than controls. Despite similar center-of-mass displacement, greater center-of-pressure displacement was observed in the intact leg during anterior–posterior perturbations, and under the prosthetic leg in medial–lateral perturbations. Further, in the prosthetic leg, ground reaction forces were smaller and spanned fewer directions. Interpretation Deficits in balance control among individuals with transtibial limb loss may be due to their inability to use their prosthetic leg to generate forces that are equal in magnitude and direction to those of unimpaired adults. Targeting this force-generating deficit through technological or rehabilitation innovations may improve balance control. [ABSTRACT FROM AUTHOR]

Abstract: Background: Rapid impulse loads imparted on the lower extremity from ground contact when landing from a jump may contribute to ACL injury prevalence in female athletes. The drop jump and drop landing tasks enacted in the first and second landings of drop vertical jumps, respectively, have been shown to elicit separate neuromechanical responses. We examined the first and second landings of a drop vertical jump for differences in landing phase duration, time to peak force, and rate of force development. Methods: 239 adolescent female basketball players completed drop vertical jumps from an initial height of 31cm. In-ground force platforms and a three dimensional motion capture system recorded force and positional data for each trial. Findings: Between the first and second landing, rate of force development experienced no change (P >0.62), landing phase duration decreased (P =0.01), and time to peak ground reaction force increased (P <0.01). Side-by-side asymmetry in rate of force development was not present in either landing (P >0.12). Interpretation: The current results have important implications for the future assessment of ACL injury risk behaviors. Rate of force development remained unchanged between first and second landings from equivalent fall height, while time to peak reaction force increased during the second landing. Neither factor was dependent on the total time duration of landing phase, which decreased during the second landing. Shorter time to peak force may increase ligament strain and better represent the abrupt joint loading that is associated with ACL injury risk. [Copyright &y& Elsevier]

Abstract: Background: In early stages, ankle osteoarthritis is often asymmetric with only partially degenerated joint surfaces. There is only limited knowledge on the effect of asymmetric ankle osteoarthritis on the patients'' gait patterns. Therefore, the aim of this study was to characterize kinematic and kinetic changes compared to healthy adults. Methods: Instrumented gait analysis was performed in eight asymmetric ankle osteoarthritis patients and 15 healthy controls. Beside conventional gait analysis methods, principal component analysis was used to analyze temporal progression of the most important variables: hindfoot dorsiflexion angle and vertical ground reaction force. Findings: Asymmetric ankle osteoarthritis patients had a lower hindfoot dorsiflexion and rotation range of motion as well as reduced peak ground reaction forces and peak kinetic values. Principal component analysis revealed that for both the hindfoot dorsiflexion angle and the vertical ground reaction force those principal component vectors affecting the amplitudes had significantly lower principal component scores in patients than in controls. The use of the principal component scores for classification with a linear support vector machine resulted in a high recognition rate of 97.8% for the discrimination between the affected leg and the healthy controls. Interpretation: Patients with asymmetric ankle osteoarthritis suffer from substantial pathological kinematic and kinetic gait changes. Principal component analysis combined with a linear support vector machine could successfully be used to temporally quantify and classify asymmetric ankle osteoarthritis gait patterns. This study therefore helps to understand the pathomechanism of early stage ankle osteoarthritis from a biomechanical view. [Copyright &y& Elsevier]

Abstract: Background: Lower-limb stress fracture is one of the most common types of running injuries. There have been several studies focusing on the association between stress fractures and biomechanical factors. In the current study, the ground reaction force and loading rate are examined. There is disagreement in the literature about whether the history of stress fractures is associated with ground reaction forces (either higher or lower than control), or with loading rates. Methods: A systematic review of the literature was conducted on the relationship between the history of tibial and/or metatarsal stress fracture and the magnitude of the ground reaction force and loading rate. Fixed-effect meta-analysis techniques were applied to determine whether or not the ground reaction force and/or loading rate are different between the stress fracture and control groups. Findings: Thirteen articles were identified through a systematic search of the literature. About 54% of these articles reported significantly different vertical ground reaction force and/or loading rate between the stress fracture and control groups. Other studies (~46%) did not observe any significant difference between the two groups. Meta-analysis results showed no significant differences between the ground reaction force of the lower-limb stress fracture and control groups (P >0.05). However, significant differences were observed for the average and instantaneous vertical loading rates (P <0.05). Interpretation: The currently available data does not support the hypothesis that there is a significant difference between the ground reaction force of subjects experiencing lower-limb stress fracture and control groups. Instead, the vertical loading rate was found to be significantly different between the two groups. [Copyright &y& Elsevier]

Abstract: Background: Although short-leg walkers are often used in the treatment of lower extremity injuries (ankle and foot fractures and severe ankle sprains), little is known about the effect the short-leg walker on gait characteristics. The purpose was to examine how heel height modifications in different short-leg walkers and shoe side may affect ground reaction forces in walking. Methods: Force platforms were used to collect ground reaction force data on 10 healthy participants. Five trials were performed in each of six conditions: lab shoes, gait walker, gait walker with heel insert on shoe side, gait walker modified with insert on walker side, equalizer walker, and equalizer walker with heel insert on shoe side. Conditions were randomized and walking speed was standardized between conditions. A 2×6 (side×condition) repeated analysis of variance was used on selected ground reaction force variables (P <0.05). Findings: The application of a walker created peak vertical and anteroposterior ground reaction forces prior to the normal peaks associated with the loading response. Wearing a walker introduced an elevated minimum vertical ground reaction force in all conditions except the equalizer walker when compared to shoe on the shoe side. Peak propulsive anteroposterior ground reaction forces were smaller in all walker conditions compared to shoe on walker side. Interpretation: The application of heel insert in gait walker with heel insert (on shoe side) and gait walker modified (on walker side) does not diminish the minimum vertical ground reaction force as hypothesized. Wearing a walker decreases the peak propulsive anteroposterior ground reaction force on the walker side and induces asymmetrical loading. [Copyright &y& Elsevier]

Abstract: Background: Tibial stress fractures are a serious overuse injury in runners. Greater vertical loading rates and tibial shock have been found in runners with previous tibial stress fracture compared to controls. The timing of these variables occurs very early in the stance phase and suggests that conditions shortly after footstrike may be important in determining injury risk. The purpose of this study was to further investigate lower extremity mechanics in early stance in runners with a history of tibial stress fracture. In addition, the relationships between these variables were explored. Methods: Twenty-three runners with a history of tibial stress fracture were investigated. They were compared with 23 age and mileage matched control subjects with no previous lower extremity bony injuries. Data were collected as subjects ran at 3.7m/s. All variables of interest were computed over the period from footstrike to the impact peak of the vertical ground reaction force. Independent t-tests and effect sizes were used to assess the differences between the groups. Pearson Product Moment correlations were used to determine whether initial stance variables were related to tibial shock in the two groups. Findings: Sagittal plane knee stiffness was significantly greater in the tibial stress fracture group. Stiffness was also positively correlated with shock. Knee excursion, knee angle at footstrike and shank angle at footstrike were not different between groups. Interpretation: These findings provide further support for the relationship between mechanics during initial loading and tibial stress fractures in runners. This relationship may be important in terms of retraining gait to reduce the risk of stress fracture in runners. [Copyright &y& Elsevier]

Abstract: Background: Recent advancements in microsurgery allow the free tissue transfer for reconstruction of soft-tissue defects on the plantar surface of the foot. Fasciocutaneous flaps are one available option to the reconstructive surgeon. However, their functional weight-bearing capabilities have never been adequately evaluated. This study investigated the dynamic loading performance of selected fasciocutaneous flaps during walking using instrumented gait analysis. Methods: We investigated 6 feet with reconstructed heels along with their contralateral normal feet. A control group of normals was included also. Time–distance, ground reaction force parameters and plantar foot pressure distribution were evaluated. Data were normalized to account for anthropometric variations. A series of t-tests were used to investigate contrasts. Findings: Walking velocity of injured subjects was decreased (P <0.0001). Step length and single limb support were the shortest for the involved feet (P <0.04). Double limb support and swing were the longest (P <0.0002). The reconstructed heels sustained high pressures (P <0.05) and vertical loadings underlining their functional weight-bearing capabilities. However, the walking patterns implemented by the injured subjects resulted in reduced anterior–posterior shear forces that could help maintain the integrity of the shear plane at the graft-recipient bed interface. Interpretation: The dynamic loading capabilities of the fasciocutaneous flaps make it an effective means for restoring functional gait. Patients implement gait patterns that result in primarily decreasing shear forces. Consequently, the fasciocutaneous flaps should be included in the surgeons’ armentarium as a plausible reconstructive means for soft-tissue defects on the plantar surface of the foot. [Copyright &y& Elsevier]

Objective. To identify changes in ground reaction force during jump landing in subjects with functional instability of the ankle joint.Design. Comparison of ground reaction force during jump landing between subjects with functional instability and healthy controls.Background. We have recently demonstrated significantly altered patterns of ankle and knee movement immediately pre- and post-impact in subjects with functional instability compared to healthy controls. We now examine the changes in timing and magnitude of forces sustained by the unstable ankle during jump landing.Methods. Fourteen subjects with unstable ankles and 10 age, sex and activity matched controls performed five single leg jumps onto a force platform whilst ground reaction forces were sampled. Timing and magnitudes of forces during the first 150 ms following impact were analysed and compared between groups.Results. Lateral and anterior force peaks occurred significantly earlier in subjects with functional instability. Significant differences were seen between groups'' time-averaged vertical, frontal and sagittal components of ground reaction force. These ranged from 5% (frontal force) to 100% (vertical force) of body mass. These changes occur immediately post-impact and too early for reflex correction/modification.Conclusions. The disordered force patterns observed in subjects with functional instability are likely to result in repeated injury due to significant increase in stress on ankle joint structures during jump landing. We suggest that they are most likely to result from deficits in feed-forward motor control.vsp sp="1">RelevanceThese results identify the potentially injurious nature of the changes in the forces applied to the unstable ankle joint during jump landing. The timing of these changes suggests that they are caused by a motor control deficit. Treatment approaches aimed at retraining feed-forward control of ankle joint movement could succeed in restoring more normal patterns of force absorption and reduce the occurrence of repeated micro-trauma to ankle structures. [Copyright &y& Elsevier]

Objective. The purpose of this study was to compare the kinematics, muscle activation, and force production between Parkinson''s patients and healthy, age-matched participants during sit-to-stand transfers.Design. This cross-sectional study employed a 2 × 2 × 3 multivariate analysis of variance to test for significant differences between and within groups.Background. The underlying mechanisms that predispose an individual to lose strength during the clinical progression of Parkinson''s disease have proved to be elusive, especially during performance of functional tasks such as the sit to stand transfer.Methods. Twenty-four men (mean age: 71.5 years) categorized as Parkinson''s patients (n=13) and healthy adults (n=11) participated in this study. Two force platforms measured antero-posterior and vertical force components as well as peak torque. Muscle activation was measured by a six channel, bilateral electromyography system. A lower-body kinematic assessment was conducted utilizing a highspeed motion analysis system.Results. No statistically significant differences were found between groups for the outcome variables measured. However, Parkinson''s patients did exhibit significant within-group bilateral differences for the variables of knee angle at seat-off, peak vertical force and peak torque.Conclusion. Data from this study reveal that persons with mild to moderate Parkinson''s disease exhibit moderately altered bilateral mechanics when performing a sit to stand transfer compared to their healthy peers.RelevanceThe inability to produce constant equilateral force when performing functional tasks could be an indicator for the increased propensity of falls or other instabilities in this population. [Copyright &y& Elsevier]

Objectives. To compare lower limb joint torques during sit-to-stand in normal elderly subjects and people with Parkinson’s disease, using a developed biomechanical model simulating all phases of sit-to-stand.Design. A cross-sectional study utilizing a Parkinsonian and a control group.Background. Subjects with Parkinson’s disease were observed to experience difficulty in performing sit-to-stand. The developed model was used to calculate the lower limb joint torques in normal elderly subjects and subjects with Parkinson’s disease, to delineate possible causes underlying difficulties in initiating sit-to-stand task.Methods. Six normal elderly subjects and seven age-matched subjects with Parkinson’s disease performed five sit-to-stand trials at their self-selected speed. Anthropometric data, two-dimensional kinematic and foot-ground and thigh-chair reactive forces were used to calculate, via inverse dynamics, the joint torques during sit-to-stand in both before and after seat-off phases. The difference between the control and Parkinson’s disease group was analysed using independent t-tests.Results. Both control and Parkinson’s disease groups had a similar joint kinematic pattern, although the Parkinson’s disease group demonstrated a slower angular displacement. The latter subjects produced significantly smaller normalized hip flexion torque and presented a slower torque build-up rate than the able-bodied subjects (P<0.05).Conclusion. Slowness of sit-to-stand in people with Parkinson’s disease could be due to a reduced hip flexion joint torque and a prolonged rate of torque production. [Copyright &y& Elsevier]

Objective. To develop an accurate method for quantifying the frequency content of the ground reaction force transient.Design. Repeated measures design comparing the impact severity during walking with different insole materials.Background. The body experiences a brief but sizeable impact upon heel strike during walking. This impact transient is believed to result in musculoskeletal injuries. It is important to accurately quantify this impact as a step towards decreasing the risk of injury.Methods. Seven subjects walked barefoot at their normal cadence across a force platform, while insole materials (Spenco, Microcel-puff, and Plastazote) were placed on the surface of the force platform. A filterbank program was developed to determine the percent root mean square in 10 Hz frequency bands from zero to 400 Hz. Analysis focused on the impact transient contained in a 20 ms window after heel contact.Results. The high frequency (>60 Hz) power was significantly larger in the barefoot condition compared to the insole conditions. The barefoot condition also resulted in significantly higher initial peak forces and force loading rates.Conclusions. The frequency content of the ground reaction force can be effectively quantified using a filterbank approach. Shoe insole materials can reduce the initial peak force, force loading rate, and frequency content of the impact transient in walking. The frequency content of the initial ground reaction force extends up to 400 Hz in some footwear conditions.Relevance The new filterbank procedure illustrates that the vertical ground reaction force in walking has a higher frequency content than previously thought. This signal requires high sampling rates to avoid aliasing, and appropriate signal processing algorithms, such as filter banks, for analysis. [Copyright &y& Elsevier]

Objective. The aim was to investigate the horizontal ground reaction forces of seated postural sway and rapid arm lift in children with and without myelomeningocele.Background. It is unclear whether children with myelomeningocele have limited control of body posture entirely caused by the impairment in the legs or also by other dysfunction.Methods. 11 children with myelomeningocele, 10–13 years, and 20 children without physical impairment were investigated. Data were collected by force plate measurements during quiet sitting and during rapid arm lift. The forces were expressed as the corresponding acceleration of the centre of mass. The amplitude and the frequency of the centre of mass acceleration quantified the sway. Movement time, onset and anteroposterior peak acceleration were analysed during arm lift.Results. The children with myelomeningocele had a low sway frequency under both conditions: eyes open and eyes closed. The movement time was longer for these children compared to the controls. The onset of initial anteroposterior centre of mass acceleration preceded the arm lift and was directed forward in both groups. The peak centre of mass acceleration was usually directed backward.Conclusions. The control of postural sway was different in children with myelomeningocele compared to children without disabilities and this could not be explained by the cele level. The children with myelomeningocele had a slow motor performance of the seated sway and during arm lift.Relevance Slow motor performance involves functional limitations in the individual child and is important for the therapy program. [Copyright &y& Elsevier]

Ground reaction forces are biomechanical data, providing information to investigate pathological gait. The vertical component of ground reaction force introduces the upward thrust force within gait progression. Although alterations in the vertical component in patients with spinal disorders were addressed in the literature, still the corresponding effect on spinal disorders is a major issue to scrutiny. In this study, the effects of two different anatomical spinal disorders on the vertical component pattern were investigated. Two groups of patients with lumbar spine stenosis and lumbar intervertebral disc degeneration with lesions at L4-L5 and/or L5-S1 levels, were recruited. The vertical component of ground reaction force and spatio-temporal parameters were obtained and analyzed using one-way analysis of variance. The results indicated that all spatio-temporal parameters differed significantly (P < 0.05) except step lengths and stride times (P > 0.05). In a similar test, the Fz2 in patients with lumbar stenosis was higher than that of those with disc degeneration (P < 0.05). Besides, the vertical ground reaction force pattern showed lower slopes in stenosis patients. This study showed that the vertical component of ground reaction force alterations and spatio-temporal parameters could be employed as indicators for certain spinal lesions. The results of this study could implement as an adjunct diagnostic method to help clinicians to differentiate between stenosis and disc degeneration patients and plan for their rehabilitation purposes. • Vertical ground reaction force was explored for lumbar spine patients. • Patients with different spinal disorders develop different force patterns in gait. • Spinal disorders affect required mechanical work and weight transfer intesity. [ABSTRACT FROM AUTHOR]

Background Biomechanical effects of anterior knee pain are difficult to distinguish from effects of other factors also related to knee injury (e.g., joint effusion). The purpose of this study was to evaluate independent effects of anterior knee pain on landing and jumping biomechanics. Methods Thirteen healthy participants performed a land and jump movement task, under three experimental conditions (pre-pain, pain, and post-pain), during one data collection session. One 1-ml injection of hypertonic saline into the infrapatellar fat pad was used to induce experimental anterior knee pain during the pain condition. Participant-perceived anterior knee pain was measured every 2 min throughout data collection. Landing and jumping biomechanics were measured and compared between the experimental conditions using a functional statistical approach. Findings The aforementioned injection increased mean participant-perceived anterior knee pain, from zero during the pre-pain condition to 2.6 ± 0.71 cm during the pain condition. Vertical ground reaction force, knee flexion angle, and internal knee extension moment decreased by approximately 0.100 body weights, 3°, and 0.010 Nm/body weight × body height, respectively, between the pre-pain and pain conditions. Conversely, hip flexion angle and internal hip extension moment increased by approximately 3° and 0.006 Nm/body weight × body height, respectively, between the pre-pain and pain conditions. Several biomechanical changes persisted after anterior knee pain abatement (the post-pain condition). Interpretation Anterior knee pain alters landing and jumping biomechanics, independent of other injury-related factors. These altered biomechanics likely change knee joint loading patterns and might increase risk for chronic knee joint injury and/or pathology. • Hypertonic saline caused experimental knee pain during a land and jump task. • This knee pain independently decreased landing vertical ground reaction forces. • Knee flexion angle and extension moment decreased due to the knee pain. • Hip flexion angle and extension moment increased due to the knee pain. [ABSTRACT FROM AUTHOR]

Children with cerebral palsy often have problems to support the body centre of mass, seen as increased ratio between excessive vertical ground reaction forces during weight acceptance and decreased forces below bodyweight in late stance. We aimed to examine whether increasing ankle range of motion through surgery and restraining motion with ankle-foot orthoses postoperatively would have impact on the vertical ground reaction force in weight acceptance and late stance. Ground reaction forces were recorded from 24 children with bilateral and 32 children with unilateral cerebral palsy, each measured walking barefoot before and after triceps surae lengthening. Postoperatively, the children were also measured walking with ankle-foot orthoses. Changes in vertical ground reaction forces between the three conditions were evaluated with functional curve and descriptive peak analyses; accounting for repeated measures and within-subject correlation. After surgery, there were decreased vertical ground reaction forces in weight acceptance and increased forces in late stance. Additional significant changes with ankle-foot orthoses involved increased vertical forces in weight acceptance, and in late stance corresponding to bodyweight (bilateral, from 92% to 98% bodyweight; unilateral, from 94% to 103% bodyweight) postoperatively. Our findings confirmed that surgery affected vertical ground reaction forces to approach more normative patterns. Additional changes with ankle-foot orthoses indicated further improved ability to support bodyweight and decelerate centre of mass in late stance. • Reduced Ben Lomonding after lower limb surgery in children with Cerebral Palsy • Improved late stance bodyweight support with Ankle-foot Orthoses versus barefoot • Vertical ground reaction forces differed between bilateral and unilateral groups. • Functional analysis enabled comparison of entire ground reaction curves between conditions. [ABSTRACT FROM AUTHOR]

The permanence of neuromuscular adaptations following anterior cruciate ligament reconstruction is not known. The aim of this study was to compare bilateral muscle co-contraction indices, time to peak ground reaction force, and timing of muscle onset between anterior cruciate ligament reconstruction subjects 10–15 years post reconstruction with those of matched uninjured controls during a one-leg hop landing. Nine healthy controls and 9 reconstruction subjects were recruited. Clinical and functional knee exams were administered. Lower limb co-contraction indices, time to peak ground reaction force, and muscle onset times were measured bilaterally. Differences in clinical and functional outcomes were assessed with unpaired t -tests, and mixed model repeated measures were used to examine effects of group, limb and interaction terms in electromyography measures. 89% of control knees were clinically "normal", whereas only 33% of reconstructed knees were "normal". Anterior cruciate ligament-reconstructed subjects tended to achieve shorter functional hop distances but demonstrated symmetrical lower limb electromyography measures that were no different from those of controls' with the exception that biceps femoris activation was delayed bilaterally prior to ground contact but was greater during the injury risk phase of landing. With the exception of hamstring activation, lower limb electromyography measures were largely similar between ligament-reconstructed and matched control subjects, which was in contrast to the clinical findings. This result brings into question the significance of neuromuscular function at this long-term follow-up but raises new questions regarding the role of symmetry and pre-injury risk. • Long-term study of anterior cruciate ligament reconstructed patients and matched controls. • Lower limb neuromuscular function was symmetrical in both groups. • Temporal hamstring activation was different between groups bilaterally. • The difference in hamstring activation was present only during the risk phase of landing. • The similarity in neuromuscular function is in contrast to the clinical findings between groups. [ABSTRACT FROM AUTHOR]