Ankle Moment Research Articles

Characterization of Motor Unit Firing and Twitch Properties for Decoding Musculoskeletal Force in the Human Ankle Joint In Vivo.

Understanding how motor units (MUs) contribute to skeletal mechanical force is crucial for unraveling the underlying mechanism of human movement. Alterations in MU firing, contractile and force-generating properties emerge in response to physical training, ageing or injury. However, how changes in MU firing and twitch properties dictate skeletal muscle force generation in healthy and impaired individuals remains an open question. In this work, we present a MU-specific approach to identify firing and twitch properties of MU samples and employ them to decode musculoskeletal function in vivo. First, MU firing events were decomposed offline from high-density electromyography (EMG) of six lower leg muscles involved in ankle plantar-dorsi flexion.We characterized their twitch responses based on the statistical distributions of their firing properties and employed them to compute MU-specific activation dynamics. Subsequently, we decoded ankle joint moments by linking our framework to a subject-specific musculoskeletal model. We validated our approach at different ankle positions and levels of activation and compared it with traditional EMG-driven models. Our proposed MU-specific formulation achieves higher generalization across conditions than the EMG-driven models, with significantly lower coefficients of variation in torque predictions. Furthermore, our approach shows distinct neural strategies across a large repertoire of contractile conditions in different muscles. Our proposed approach may open new avenues for characterizing the relationship between MU firing and twitch properties and their influence on force capacity. This can facilitate the development of targeted rehabilitation strategies tailored to individuals with specific neuromuscular conditions.

Design of a Flexible Bionic Ankle Prosthesis Based on Subject-specific Modeling of the Human Musculoskeletal System

A variety of prosthetic ankles have been successfully developed to reproduce the locomotor ability for lower limb amputees in daily lives. However, they have not been shown to sufficiently improve the natural gait mechanics commonly observed in comparison to the able-bodied, perhaps due to over-simplified designs of functional musculoskeletal structures in prostheses. In this study, a flexible bionic ankle prosthesis with joints covered by soft material inclusions is developed on the basis of the human musculoskeletal system. First, the healthy side ankle–foot bones of a below-knee amputee were reconstructed by CT imaging. Three types of polyurethane rubber material configurations were then designed to mimic the soft tissues around the human ankle, providing stability and flexibility. Finite element simulations were conducted to determine the proper design of the rubber materials, evaluate the ankle stiffness under different external conditions, and calculate the rotation axes of the ankle during walking. The results showed that the bionic ankle had variable stiffness properties and could adapt to various road surfaces. It also had rotation axes similar to that of the human ankle, thus restoring the function of the talocrural and subtalar joints. The inclination and deviation angles of the talocrural axis, 86.2° and 75.1°, respectively, as well as the angles of the subtalar axis, 40.1° and 29.9°, were consistent with the literature. Finally, dynamic characteristics were investigated by gait measurements on the same subject, and the flexible bionic ankle prosthesis demonstrated natural gait mechanics during walking in terms of ankle angles and moments.

Mechanisms that stabilize human walking


 
 
 In this paper we review what mechanisms are used to stabilize human bipedal gait. Based on mechanical reasoning, potential mechanisms to control the body center of mass trajectory are modulation of foot placement, stance leg control consisting of modulation of ankle moments and push-off forces, and modulations of the body’s angular momentum. The first two mechanisms and especially the first are dominant in controlling center of mass accelerations during gait, while angular momentum control plays a lesser role, but may be important to control body alignment and orientation. The same control mechanisms stabilize both steady-state and perturbed gait in both the mediolateral and antero-posterior directions. Control is at least in part active and is affected by proprioceptive, visual and vestibular information. Results support that this reflects a feedback process in which sensory information is used to obtain an estimate of the center of mass state based on which foot placement and ankle moments are modulated. These active feedback mechanisms suggest training approaches for populations at risk of falling, such as augmenting their effective use by means of augmented feedback, or using their complementary nature to train one mechanism by constraining the other mechanisms.
 
 

Is Intermittent Control the Source of the Non-Linear Oscillatory Component (0.2-2Hz) in Human Balance Control?

To explain the 0.2-2Hz oscillation in human balance. Oscillation (0.2-2 Hz) in the control signal (ankle moment) is sustained independently of external disturbances and exaggerated in Parkinson's disease. Does resonance or limit cycles in the neurophysiological feedback loop cause this oscillation? We investigate two linear (non-predictive, predictive) and one non-linear (intermittent-predictive) control model (NPC, PC, IPC). Fourteen healthy participants, strapped to an actuated single segment robot with dynamics of upright standing, used natural haptic-visual feedback and myoelectric control signals from lower leg muscles to maintain balance. An input disturbance applied stepwise changes in external force. A linear time invariant model (ARX) extracted the delayed component of the control signal related linearly to the disturbance, leaving the remaining, larger, oscillatory non-linear component. We optimized model parameters and noise (observation, motor) to replicate concurrently (i) estimated-delay, (ii) time-series of the linear component, and (iii) magnitude-frequency spectrum and transient magnitude response of the non-linear component. Results (mean±S.D., p<0.05): NPC produced estimated delays (0.116±0.03s) significantly lower than experiment (0.145±0.04s). Overall fit (i)-(iii) was (79±7%, 83±7%, 84±6% for NPC, PC, IPC). IPC required little or no noise. Mean frequency of experimental oscillation (0.99±0.16 Hz) correlated trial by trial with closed loop resonant frequency (fres), not limit cycles, nor sampling rate. NPC (0.36±0.08Hz) and PC (0.86±0.4Hz) showed fres significantly lower than IPC (0.98±0.2Hz). Human balance control requires short-term prediction. IPC mechanisms (prediction error, threshold related sampling, sequential re-initialization of open-loop predictive control) explain resonant gain without uncontrolled oscillation for healthy balance.

Individuals with Bilateral Cerebral Palsy Rely On Excessive Hip Extension To Complete A Step-Up Task

<h3>Research Objectives</h3> To investigate the hip, knee, and ankle joint moments of individuals with bilateral cerebral palsy (CP) during a step-up task. Due to distal joint impairment, we hypothesized that individuals with bilateral CP would generate less knee and ankle moments and more hip moments when stepping up than individuals without CP. <h3>Design</h3> In this cross-sectional study, participants were instructed to step up onto a 10.2-cm platform 5-15 times with the same leading limb. <h3>Setting</h3> University gait laboratory. <h3>Participants</h3> We recruited from convenience samples of individuals with and without bilateral CP between 5-19 years of age. Individuals without bilateral CP (n=11, 6 females, mean age=12.8 years) were included if they had no known neurological conditions. Individuals with bilateral CP (n=5, 1 female, mean age=10.6 years) were included if they had some ambulatory function without assistive devices or orthotics, no botulinum toxin injections in the past 6 months, no lower limb surgeries in the past year, and no serious co-morbidities. <h3>Interventions</h3> N/A. <h3>Main Outcome Measures</h3> Extensor support moments were calculated by summing normalized hip, knee, and ankle sagittal plane moments. Peak support moments were identified in the push-off and pull-up stance phases, where typically the ankle and knee joints generate the highest moments, respectively. Individual joint contributions to peak support moments were averaged and compared between groups using a Welch's t-test. <h3>Results</h3> For the push-off phase, the difference in hip extension moments was significant between groups, where individuals with bilateral CP generated larger hip moments during peak support moments compared to individuals without bilateral CP (p< 0.001, CI: [0.445 0.798] Nm/kg). For the pull-up phase, differences in hip and knee extension moments were significant between groups. Individuals with bilateral CP generated larger hip moments (p< 0.001, CI: [0.364 0.911] Nm/kg) and smaller knee moments (p=0.007, CI: [-0.729 -0.161] Nm/kg) during peak support moments compared to individuals without bilateral CP. <h3>Conclusions</h3> Increased generation of hip extension moments during a step-up task is likely a neural and biomechanical compensation for distal joint impairment in individuals with bilateral CP. <h3>Author(s) Disclosures</h3> None.

Biomechanical Characteristics and Metabolic Efficiency of Gait in Young-old and Old-old People

<h3>Research Objectives</h3> To investigate and compare the biomechanical characteristics and cardiopulmonary metabolic energy efficiency of gait between the young-old and the old-old community dwelling people. <h3>Design</h3> Cross-sectional study. <h3>Setting</h3> Clinical experimental study. <h3>Participants</h3> The elderly participants (N=78) were classified into the young-old (age range=65-74, mean age=70.2 ± 2.8 years, n=44) and the old-old (age range=75-84, mean age=77.9 ± 2.2 years, n=34) groups. <h3>Interventions</h3> Not applicable. <h3>Main Outcome Measures</h3> Spatiotemporal parameters (gait speed, cadence, step length, step width, and stride length), kinematics (angle of hip, knee, and ankle joint), kinetics (moment and power of hip, knee, and ankle joint), and cardiopulmonary metabolic energy efficiency during gait. <h3>Results</h3> Spatiotemporal gait parameters (gait speed, step length, and stride length) were significantly decreased in the old-old compared to the young-old group (p < 0.01). Peak ankle dorsiflexion angle, peak moment and peak power of knee and hip joints during gait were also significantly decreased in the old-old compared to the young-old group (p < 0.05, p < 0.01). On the other hand, net cardiopulmonary metabolic energy cost showed no significant difference between groups. <h3>Conclusions</h3> The old-old and young-old people showed significantly different gait characteristics, which suggested a need of customized intervention strategy in two elderly groups for preventing age-related hazardous condition such as fall. <h3>Author(s) Disclosures</h3> Eunhye Chung1,2, Su-Hyun Lee2, and Yun-Hee Kim1,2,3 1. Department of Medical Device Management & Research, SAIHST, Sungkyunkwan University, SAIHST, Seoul, Republic of Korea 2. Department of Physical and Rehabilitation Medicine, Center for Prevention and Rehabilitation, Heart Vascular Stroke Institute, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Republic of Korea 3. Department of Health Sciences and Technology, Department of Digital Health, Sungkyunkwan University, SAIHST, Seoul, Republic of Korea

Potentiation of Stretch Shortening Cycle of Hip Moment and Power Only predict Jump Performance Enhancement

<h3>Research Objectives</h3> To investigate if lower-extremity joint specific potentiation of stretch shortening cycle (SSC) during the propulsive phase of jump test predicts jump height. <h3>Design</h3> Cross-sectional study. <h3>Setting</h3> University research laboratory. <h3>Participants</h3> Twenty-two young adults (12 females; mean age=25.75±3.03 years). <h3>Interventions</h3> Not applicable. <h3>Main Outcome Measures</h3> Participantsperformed three countermovement jump (CMJ) and static Jump (SJ) and bent their knees to the same flexion degree on two floor-embedded force platforms (AMTI). Using a 3-dimensional (3D) motion capture system (Vicon), jump height (JH) was measured using greater trochanters markers data of both lower extremities. Joint-based moment (Jmom) and power (Jpwr) of hip, knee, and ankle were calculated. Potentiation of SSC was calculated as CMJ/SJ ratios of JH, Jmom, and Jpwr for hip, knee, and ankle. The Vicon system contains 11 infrared cameras and two force platforms to synchronize kinetic and kinematic data. Linear regression models were used to examine if SSC potentiation predicts JH, controlling for knee joint angle and sex. <h3>Results</h3> JHPotentiation was 1.30±0.24. SSC Jmom potentiation was 1.33±0.40, 1.04±0.13, and 1.02±0.12 for hip, knee, and ankle, respectively. SSC Jpwr Potentiation was 1.39±0.53, 1.03±0.18, and 1.02±0.18 for hip, knee, and ankle, respectively. The regression models documented that SSC potentiation of hip Jpwr and Jmom predicted 77% and 87% of the variance in JH, respectively, after controlling for knee joint angle and sex. No other significant JH predictors were identified (p>0.05). <h3>Conclusions</h3> The findings show that hip Jmom and Jpwr SSC potentiation were associated with Jump test performance during the propulsive phase These findings provide an insight into understanding the mechanical function of the contribution of SSC potentiation of the lower extremities to jump tests performance. <h3>Author(s) Disclosures</h3> All authors declare no conflicts.

Effects of movement direction and limb dominance on ankle muscular force in sidestep cutting.

Sidestep cutting is a critical movement in sports. However, biomechanical research on sidestep cutting has not hitherto reached a consensus. In order to investigate the effects of limb dominance and movement direction on ankle and subtalar joints during sidestep cutting, twelve physically active male participants were recruited in the present study. Trajectory and ground reaction force data were collected by the motion capture system and force platform. Kinematics, kinetics, and muscle forces information were obtained by running OpenSim. Two-way repeated measures ANOVA was performed with movement direction and limb dominance as independent variables. We found that movement direction had a significant effect on ankle dorsiflexion angle. In contrast, the factor of limb dominance had no effect on ankle and subtalar joints angles. For ankle joint moment, the plantarflexion moment was greater by performing a 45° sidestep cutting or using the dominant limb, while the subtalar joint moment was not affected by these two variables. In terms of muscle forces, the soleus of the dominant limb generated greater plantarflexion muscle force on the sagittal plane, while the non-dominant limb tended to contract more strongly (peroneus longus and peroneus brevis) on the frontal plane to stabilize the subtalar joint. Meanwhile, a smaller sidestep cutting angle made participants generate greater plantarflexion muscle forces (soleus and gastrocnemius). In conclusion, our findings indicated that participants should take limb dominance and movement direction into consideration for enhancing athletic performance and reducing the risk of injury during sidestep cutting.

The Effects of Cadence Manipulation on Joint Kinetic Patterns and Stride-to-Stride Kinetic Variability in Female Runners.

Altering running cadence is commonly done to reduce the risk of running-related injury/reinjury. This study examined how altering running cadence affects joint kinetic patterns and stride-to-stride kinetic variability in uninjured female runners. Twenty-four uninjured female recreational runners ran on an instrumented treadmill with their typical running cadence and with a running cadence that was 7.5% higher and 7.5% lower than typical. Ground reaction force and kinematic data were recorded during each condition, and principal component analysis was used to capture the primary sources of variability from the sagittal plane hip, knee, and ankle moment time series. Runners exhibited a reduction in the magnitude of their knee extension moments when they increased their cadence and an increase in their knee extension moments when they lowered their cadence compared with when they ran with their typical cadence. They also exhibited greater stride-to-stride variability in the magnitude of their hip flexion moments and knee extension moments when they deviated from their typical running cadence (ie,running with either a higher or lower cadence). These differences suggest that runners could alter their cadence throughout a run in an attempt to limit overly repetitive localized tissue stresses.

Surgical Management of Severe Equinus Deformity in Ambulatory Children With Cerebral Palsy.

Tendo Achilles lengthening (TAL) for the management of equinus contractures in ambulatory children with cerebral palsy (CP) is generally not recommended due to concerns of over-lengthening, resulting in weakness and plantar flexor insufficiency. However, in some cases, surgical correction of severe equinus deformities can only be achieved by TAL. The goal of this study is to assess the outcomes following TAL in these cases. A retrospective cohort study of children with CP with severe equinus contractures (ankle dorsiflexion with the knee extended of -20 degrees or worse) who underwent TAL as part of a single event multilevel surgery, with preoperative and postoperative gait analysis studies. Continuous data were analyzed by paired t test, and categorical data by McNemar Test. There were 60 subjects: 42 unilateral, 18 bilateral CP; 41 GMFCS II, 17 GMFCS I; mean age at surgery was 10.6 years, mean follow-up was 1.3 years. Ankle dorsiflexion with the knee extended improved from -28 to 5 degrees (P<0.001). The ankle Gait Variable Score improved from 34.4 to 8.6 (P<0.001). The ankle moment in terminal stance improved from 0.43 to 0.97Nm/kg (P<0.001). Significant improvements (P<0.001) were seen in radiographic measures of foot alignment following surgery. There were few significant differences in the outcome parameters between subjects with unilateral versus bilateral CP (eg, only the bilateral group showed improved but persistent increased knee flexion in mid-stance). The outcomes following TAL for the management of severe equinus deformity in ambulatory children with CP were favorable 1 year after surgery, with significant improvements in all domains measured. This study does not advocate for the widespread use of TAL to correct equinus deformity in children with CP. However, it does show that good short-term outcomes following TAL are possible in properly selected subjects with severe contractures when the dosing of the surgery is optimal (correction of contracture to between 0 and 5 degrees of dorsiflexion with the knee extended) and the procedure is performed in the setting of single event multilevel surgery with subsequent proper orthotic management and rehabilitation.

Postural balance strategies during landing at the moment of return-to-sports after anterior cruciate ligament reconstruction

Most athletes that return to sport (RTS) after Anterior Cruciate Ligament (ACL) injury undergo reconstruction (ACLR) to restore their knee stability. The major concern for RTS is for the patient to be able to perform challenging dynamic tasks whilst adequately stabilizing the knee joint and maintaining their postural balance. Nevertheless, the interaction between knee protective mechanisms (such as knee unloading and knee stabilisation) and postural balance strategies has not yet been comprehensively analyzed. Thus, the aim of this study was to investigate landing balance strategies in ACLR athletes at time of RTS. Twenty-one athletes with a unilateral ACLR were tested at the time of RTS while performing a single leg hop for distance on both limbs. Three balance mechanisms that influence the GRF during the landing phase (foot placement, center of pressure (CoP) excursion, counter-rotation of segments) were investigated and compared between the ACL injured and uninjured limb. Interactions between knee protective mechanisms and postural balance strategies were tested using a statistical parametric mapping regression analysis. Results show that CoP excursions in the injured limb increased, as well as ankle joint moment contribution to anterior-posterior (A-P) GRF. Besides, patients presenting reduced knee joint contribution to A-P GRF had to compensate with higher hip joint contribution in order to maintain postural balance. In conclusion, ACLR athletes who at RTS still protect their reconstructed knee are forced to employ compensatory postural balance strategies. Therefore, there is a persistent trade-off between knee protection and postural balance at the moment of RTS.

Ambulatory support moment contribution patterns and MRI-detected tibiofemoral and patellofemoral disease worsening in adults with kneeosteoarthritis: A preliminary study.

We investigated whether baseline sagittal-plane ankle, knee, and hip contribution to the total support moment (TSM) are each associated with baseline-to-2-year tibiofemoral and patellofemoral tissue damage worsening in adults with knee osteoarthritis. Ambulatory lower-limb kinetics were captured and computed. TSM is the sum of ankle, knee, and hip extensor moments at each instant during gait. Ankle, knee, and hip contributions to TSM were computed as joint moments divided by TSM, expressed as percentages. Participants underwent MRI of both knees at baseline and 2years later. Logistic regression models assessed associations of baseline ankle contribution to TSM with baseline-to-2-year cartilage damage and bone marrow lesion worsening, adjusted for age, sex, BMI, gait speed, disease severity, and pain. We used similar analytic approaches for knee and hip contributions to TSM. Sample included 391 knees from 204 persons (age[SD]: 64[10]years; 76.5% women). Greater ankle contribution may be associated with increased odds of tibiofemoral cartilage damage worsening (OR = 2.38; 95% CI: 1.02-5.57) and decreased odds of patellofemoral bone marrow lesion worsening (OR = 0.14; 95% CI: 0.03-0.73). The ORs for greater knee contribution were in the protective range for tibiofemoral compartment and in the deleterious range for patellofemoral. Greater hip contribution may be associated with increased odds of tibiofemoral worsening (OR = 2.71; 95% CI: 1.17-6.30). Greater ankle contribution to TSM may be associated with baseline-to-2-year tibiofemoral worsening, but patellofemoral tissue preservation. Conversely, greater knee contribution may be associated with patellofemoral worsening, but tibiofemoral preservation. Preliminary findings illustrate potential challenges in developing biomechanical interventions beneficial to both tibiofemoral and patellofemoral compartments.

Females with hip-related pain display altered lower limb mechanics compared to their healthy counterparts in a drop jump task

BackgroundHip-related pain describes femoroacetabular impingement syndrome, acetabular dysplasia, and other hip pain conditions without clear morphological features. Movement strategies in this population, notably sex-related patterns, are poorly understood and may provide insights into why females report more pain and worse function. This study examined the sex-related differences during a drop vertical jump task between those with hip-related pain and healthy controls. MethodsPatients with hip-related pain and healthy controls completed five repetitions of a drop jump while their kinematics and kinetics were recorded using a motion capture system and force plates. Hip, knee, and ankle joint angles and external joint moments during landing were used in general estimating equations for comparison of group by sex by limb interactions. Time series data were further investigated using statistical parametric mapping. Findings: Females with hip-related pain had 9.1° less hip flexion (P = .041) and 9.2° less knee flexion (P = .024) than healthy females, and 8.3° less knee flexion than male counterparts with hip-related pain (P = .039). Males demonstrated 1.4° less hip flexion on the affected side compared to their uninvolved side (P = .004). Statistical parametric mapping results showed significant differences in knee flexion angle for females with hip-related pain compared to healthy females (P = .042). There were no significant differences in hip, knee, or ankle moments. InterpretationFemales with hip-related pain showed kinematic patterns distinct from healthy controls. Sex may be an important variable of interest in characterizing movement impairments in this population and movement impairments may be an appropriate target for intervention for these patients.

Independently ambulatory children with spina bifida experience near-typical knee and ankle joint moments and forces during walking

BackgroundSpina bifida, a neurological defect, can result in lower-limb muscle weakness. Altered ambulation and reduced musculoskeletal loading can yield decreased bone strength in individuals with spina bifida, yet individuals who remain ambulatory can exhibit normal bone outcomes. Research questionDuring walking, how do lower-limb joint kinematics and moments and tibial forces in independently ambulatory children with spina bifida differ from those of children with typical development? MethodsWe retrospectively analyzed data from 16 independently ambulatory children with spina bifida and 16 children with typical development and confirmed that tibial bone strength was similar between the two groups. Plantar flexor muscle strength was measured by manual muscle testing, and 14 of the children with spina bifida wore activity monitors for an average of 5 days. We estimated tibial forces at the knee and ankle using motion capture data and musculoskeletal simulations. We used Statistical Parametric Mapping t-tests to compare lower-limb joint kinematic and kinetic waveforms between the groups with spina bifida and typical development. Within the group with spina bifida, we examined relationships between plantar flexor muscle strength and peak tibial forces by calculating Spearman correlations. ResultsActivity monitors from the children with spina bifida reported typical daily steps (9656 [SD 3095]). Despite slower walking speeds (p = 0.004) and altered lower-body kinematics (p < 0.001), children with spina bifida had knee and ankle joint moments and forces similar to those of children with typical development, with no detectable differences during stance. Plantar flexor muscle weakness was associated with increased compressive knee force (p = 0.002) and shear ankle force (p = 0.009). SignificanceHigh-functioning, independently ambulatory children with spina bifida exhibited near-typical tibial bone strength and near-typical step counts and tibial load magnitudes. Our results suggest that the tibial forces in this group are of sufficient magnitudes to support the development of normal tibial bone strength.

Comparison of Joint-Level Kinetics During Single-Leg and Double-Leg Weightlifting Derivatives.

Hayashi, R, Yoshida, T, and Kariyama, Y. Comparison of joint-level kinetics during single- and double-leg weightlifting derivatives. J Strength Cond Res 37(5): 1017-1022, 2023-Humans have different 3-dimensional biomechanical characteristics of the lower extremities during locomotion with one and both legs. These biomechanical characteristics may also be observed in the weightlifting derivatives. This study aimed to compare the 3-dimensional joint kinetics of the lower extremities during the single-leg hang power clean (SHPC) and double-leg hang power clean (DHPC). Ten male track and field athletes performed the SHPC and DHPC using external loads of 30, 60, and 90% of one repetition maximum (1RM). The 1RMs in SHPC and DHPC were measured separately, and the external loads at 30, 60, and 90% of the 1RM used were determined based on the different 1RMs in SHPC and DHPC. We calculated the joint moment and joint power of the SHPC and DHPC using a motion capture system and force platforms. The hip abduction moment and power of the SHPC were significantly greater than those of the DHPC under all external loads ( p < 0.05). In addition, ankle joint moment at all external loads and joint power at 90% of 1RM was greater for SHPC than for DHPC ( p < 0.05). Furthermore, although hip (extension-flexion) and ankle joint kinetics in SHPC and DHPC showed similar load dependence, hip abduction axis kinetics was not load dependent. These results suggest that the hip (abduction-adduction) and ankle joint kinetics in SHPC are greater than in DHPC, but hip (abduction-abduction) kinetics in SHPC is not load independent.

Differential effects of ankle constraints on foot placement control between normal and split belt treadmills

Mediolateral ankle moment control contributes to gait stability. Ankle moments can be constrained by walking with a shoe with a ridge underneath the sole, narrowing the mediolateral support surface. In our previous study, such ankle moment constraints resulted in an increased step width and a decrease in the degree of foot placement control, as defined by the percentage of variance in foot placement that can be explained by CoM state. However, since our previous study was performed on a split-belt treadmill and the narrow ridge could fit inside the gap between the belts, it is not evident whether these effects can be attributed to the constrained ankle moment control or to avoidance of this gap. Therefore, we investigated if the effects of ankle moment constraints are dependent on whether participants walk on a normal treadmill or a split-belt treadmill. We included fourteen healthy young adults. Walking with constrained ankle moment control resulted in a wider step width on both treadmills. Yet, the increase in step width was larger on the split-belt treadmill compared to on the normal treadmill. We only found a decreased degree of foot placement control on the split-belt treadmill, whilst the degree of foot placement control increased on the normal treadmill. We conclude that the effects of ankle moment constraints reported in our previous study were confounded by the use of a split-belt treadmill. For future research, we recommend using a normal treadmill whenever possible, because the gap in a split-belt treadmill might affect gait parameters.

Immediate Effects of Manipulating Footwear or Cadence on the Lower Limb Biomechanics of Female Masters Runners.

The objective of this study was to compare the immediate effects of modifications to footwear or cadence on lower limb biomechanics of female Masters runners. After analyzing habitual treadmill running biomechanics in 20 female runners (52.4 [8.3]y), we assessed the effects of 5 conditions: (1)barefoot running, (2)Merrell Vapor Glove, (3)Merrell Bare Access, (4)Brooks Pure Flow, and (5)increasing cadence by 10%. In comparison with habitual biomechanics, greater vertical loading rates of the ground reaction force were observed during running barefoot or with a Merrell Vapor Glove or Bare Access. There was high variability among participants as to changes in foot kinematics during the conditions. Running barefoot (-26.0%) and with a Merrell Vapor Glove (-12.5%) reduced sagittal plane knee moments, but increased sagittal plane ankle moments (both 6.1%). Increasing cadence by 10% resulted in a more modest decrease in knee flexion moments (-7.7%) without increasing peak external ankle dorsiflexion moments. When asked if they would prefer minimalist shoes or increasing cadence, 11 participants (55%) chose cadence and 9 (45%) chose footwear. Minimalist footwear decreased sagittal knee moments, but increased vertical loading rate and sagittal ankle moments. Increasing cadence may be useful to lower sagittal knee moments without increasing ankle moments.

The Effect of Visual Biofeedback Balance Training on Time to Stabilization and Kinetic Variables in Patients with Chronic Ankle Instability

PURPOSE This study aimed to analyze the dynamic posture stabilization and kinematic variables between visual feedback and Y-balance training groups during jump-landing. METHODS Thirty-eight male players (age: 22.6 ± 1.12 years, height: 175 ± 3.54 cm, weight: 65.5 ± 5.11 kg) were included in this study, and chronic ankle instability was checked using Cumberland Ankle Instability Tool (CAIT) and Balance Error Scoring System (BESS). They were randomly assigned to the Visual biofeedback (Training group: TG, n = 19) and Y-balance groups (Control group: CG, n = 19) for four weeks. TG performed balance training using the Biodex balance system (BBS) and CG performed training using the Y-balance system. During jump landing, time to stabilization (TTS), force plate (COP, GRF); joint angle and moment were collected and analyzed. All analyses were performed with SPSS 21.0, and Bonferroni was used for repeated measured ANOVA and post-hoc. RESULTS The results indicated that there was an interaction between TG and CG in terms of AP and ML directions of TTS (&lt;i&gt;p&lt;/i&gt; &lt; 0.05). AP/ML TTS of the TG for the post-test was smaller than that for CG (AP: &lt;i&gt;p&lt;/i&gt; = 0.000; ML: &lt;i&gt;p&lt;/i&gt; = 0.046). ML TTS of the TG for post-test was smaller than at pre-test (&lt;i&gt;p&lt;/i&gt; = 0.041), and AP TTS of the CG for ankle joint moment (&lt;i&gt;p&lt;/i&gt; &lt; 0.05). There was an interaction between TG and CG in terms of dorsiflexion (DF) and plantarflexion (PF) of joint moment (&lt;i&gt;p&lt;/i&gt; &lt; 0.05). Ankle moment of the CG for post-test decreased than at pre-test (DF: &lt;i&gt;p&lt;/i&gt; = 0.040, PF: &lt;i&gt;p&lt;/i&gt; = 0.032), and ankle dorsiflexion moment of the CG for post-test was decreased than at pre-test (&lt;i&gt;p&lt;/i&gt; = 0.046). CONCLUSIONS Balance ability was achieved more effectively through visual biofeedback training than Y-balance training. Therefore, we recommend balanced training with visual feedback on chronic ankle instability.

Predicting post-total ankle arthroplasty walking speed based on preoperative gait mechanics.

Decreased walking speed is associated with impaired physical performance and function in older adults. Following total ankle arthroplasty (TAA), walking speed continues to be slower than age matched controls. The purpose of this study was to determine if patients 1 year post-TAA can achieve walking speed benchmarks and investigate if gait metrics are predictive of achieved benchmarks. 191 TAA patients were recruited and assessed pre-TAA and 1 year post-TAA. Kinetic and kinematic data were collected during seven self-selected speed barefoot walking trials along a 30-mwalkway. Receiver operator curveswere generated for each variable to determine threshold values needed to achieve walking speeds of 0.8, 0.9, 1.1, and 1.3 m/s. Each variable's predictive ability was classified according to the area under the curve. Ninety one percent of participants achieved a walking speed > 0.8 m/s, 85.3% achieved ≥0.9 m/s, 64.9% walked at ≥1.1 m/s, and 24.1% achieved a walking speed of 1.3 m/s by 1 year post-TAA. Walking speed pre-TAA was the strongest predictor with ankle moment, power and GRF data showing mixed results. Clinical Significance: 75.9% of participants were unable to walk at 1.3 m/s-a speed indicative of safely crossing a street. Variables predictive of postoperative walking speed benchmarks could be useful in developing interventions for the TAA population. The strongest predictor across all walking speed benchmarks was preoperative walking speed. A walking speed > 0.71 m/s was predictive of achieving 0.8 m/s 1 year post-TAA, while >1.09 m/s predicted 1.3 m/s 1 year post-TAA.

A two-stage disto-proximal braking modality to interrupt gait initiation in healthy adults

The purpose of this investigation was to determine the effect of unexpected gait termination in able-bodied participants during gait initiation on spatiotemporal and stance limb biomechanical parameters.Twenty-one healthy adults took part in this study and were divided into two groups based on the natural anterior or posterior incline of their trunk. Each participant performed 15 random trials of gait initiation: 10 trials with a Go signal and 5 with Go-&-Stop signals. Spatiotemporal parameters were assessed between the Go signal and the first heel contact. Ankle, knee, and hip joint moments were calculated in the sagittal plane. Free moment and impulse were also calculated for the stance limb.Spatiotemporal parameters were not influenced by the mean trunk inclination (p > 0.05), but participants with a forwardly-inclined trunk presented higher hip extension moments (p < 0.05). Unexpected stopping required smaller ankle and knee moments compared to the Go condition (p < 0.05). The hip extension moments appeared to be independent of gait initiation conditions (p > 0.05). The capacity of able-bodied people to interrupt their gait initiation relied on a two-stage disto-proximal braking modality involving explosive motor patterns at the ankle and hip joints.Such a pattern could be altered in vulnerable people, and further studies are needed to investigate this. This study determined a clinical method applicable as a functional protocol to assess and improve the postural control of people suffering from a lack of motor modulation during crucial transient tasks. Such tasks are essential in activities of daily living.