Ankle Strategy Research Articles

Hip Abductor Muscle Fatigue Induces Different Strategies During Disrupted Postural Control.

BackgroundAnkle sprain is one of the most common injuries in sport, and hip abductor muscle weakness has recently been reported as a predisposing factor. Currently, the influence of hip abductor muscle fatigue on ankle joint control has not been elucidated during an ankle disturbed balance exercise. This study aimed to determine the influence of hip abductor muscle fatigue on ankle joint control during a disturbed balance task, and to consider inter-individual variability in the kinematic and neuromuscular reorganizations implemented.MethodsTwenty-six healthy subjects (13 males; 13 females) performed a unipedal postural balance task with eyes closed before and after a fatiguing exercise (up to a 50% decrease in strength) of the hip abductor muscles. Subjects completed balance task while equipped with an ankle destabilization device that allows inversion/eversion movements. Electromyographic (EMG) activity of the gastrocnemius lateralis (GastL), peroneus longus (PL) and brevis, tibialis anterior, and gluteus medius were recorded during task. Kinematics (e.g., frontal foot angulation) of the ankle complex were determined using inertial measurement units.ResultsIn the overall group, no significant time, sex or interaction effect was observed for kinematic and EMG variables. However, when considering individual responses to hip fatigue, 14 subjects decreased the standard deviation of frontal angulation (−30%) suggesting enhancement of ankle joint control, while 12 subjects increased it (+46%). Normalized EMG for PL and GastL muscles changed with fatigue for both these groups. However, variations were significantly different between groups (p = 0.027 for PL and p = 0.006 for GastL). Indeed, the contribution of ankle muscles increased for the enhanced-stability group while no change for the impaired-stability group.ConclusionThese results highlight that subject adopt different neuromuscular and kinematic ankle strategies to control ankle destabilization in response to hip abductor muscle fatigue. Frontal foot angulation variability seemed to be a valuable marker to detect the type of strategy employed. The strategy adopted by the impaired-stability group might have important implications when analyzing risk factors for ankle sprains. Further studies should consider individual responses to fatigue, to understand which factor could predispose athletes to use of one or other strategy.

Impact of age on the postural stability measured by a virtual reality tracker-based posturography and a pressure platform system

BackgroundCenter of pressure (CoP) parameters are commonly used to evaluate age-related changes in postural control during standing. However, they mainly reflect ankle strategies and provide limited information about hip strategies, which are essential for postural control among the aged population. Body displacement at the lumbar level (LD) can be used as a proxy for hip strategies.ObjectivesWe set up a virtual reality tracker-based posturography to measure LD and compared the CoP and LD parameters in two age groups to explore the roles of ankle and hip strategies during bipedal stance.MethodsTwenty-seven older healthy participants (63.8 ± 7.1 years old) and 27 younger controls (31.7 ± 9.9 years old) performed four standing tasks with their postural steadiness measured simultaneously with both systems under four stance conditions (combination of eyes-open/eyes-closed and wide-based/narrow-based). Five parameters were calculated from the trajectories of the CoP and LD. The difference in the parameters between two groups was analyzed with the Mann–Whitney U test. The discriminative ability of the parameters from the two systems was computed by the receiver operating characteristic curve analysis and area under the curve (AUC). We also used the intraclass correlation coefficient (ICC) to assess the correlation between two measures.ResultsMost of the parameters obtained from both systems were significantly different between the younger and older groups. Mean velocity in the medial–lateral and anterior–posterior directions could effectively discriminate age-related changes, especially with the LD parameters. The receiver’s operation curve analysis gained the largest AUC (0.85 with both systems) with mean velocity in the medial–lateral direction during narrow-based standing with eyes closed. Meanwhile, we observed a low correlation between parameters obtained from the two methods in velocity measures, with the lowest ICC in the mean velocity in the medial–lateral direction in the older group (ICC = 0.34 ~ 0.41).ConclusionBoth systems could differentiate age-related changes in postural steadiness, but with dissociated information about mean velocity, especially the mean velocity in the medial–lateral direction in the older group. The results support the complimentary role of using tracker-based posturography to understand the effect of age on the mechanisms of postural control.

Dual-Motor Balance Tasks Prompts Slight Lower Limb Neuromuscular Adaptations in Healthy Young Adults

Previous literature has analyzed muscular recruitment patterns in various populations during complex balance conditions that involve a secondary task. This inquiry seeks to determine whether challenging sensory systems in young adults during single and dual-motor tasks can prompt modifications in neuromuscular patterns at the hip and leg musculature. Our study included twenty-nine healthy young adults (3 males and 25 females) with an average age of 24.3+/-2.4. Electromyography (EMG) electrodes were used to collect EMG data, and the variables of interest include the onset of muscle contraction, the decay of muscle contraction, peak muscle activation, and duration of muscle contraction. Five balance activities were conducted while performing a dual-motor task, while sensory input was altered in each condition. No significant changes in EMG activity were observed in the gastrocnemius (GA) and (TA) muscle activity. However, a tendency was observed in the onset and duration values of the gluteal muscles. Recruitment of the TA and GA remained uniform across variables, but gluteus maximus (GMax) and medius (GMed) activity appeared sooner (onset) and lasted longer (duration). Comparability in muscle recruitment during dual-task balance activities indicates healthy young adults can successfully rely on other sensory systems for balance when one or more networks are altered. Increases in GA and TA activity suggested a greater need for ankle strategies during the condition trials, while increased GMax and GMed activity indicated the same for hip strategies. Further research should examine joint kinematic to discern any adaptations during dual-motor tasks in young, healthy adults.

Evaluation of posturographic indicators in children with non-purulent acute otitis media

Nowadays otitis media still remains one of the most common diseases of the middle ear in children [1]. The interconnection between otitis media and its effect on vestibular function in children has not been thoroughly studied yet. The aim of the study is to conduct a comparative analysis of stabilometric indicators of preschool children, diagnosed with non-purulent acute otitis media, and their relatively healthy typically developed peers. Materials and methods: 22 children, diagnosed with non-purulent acute otitis media, and their 25 relatively healthy typically developed peers aged 4 to 7, have been examined on the device "MPFI Stabilograph 1" (AS-TER IT, LLC, Kharkiv, Ukraine). The research has taken into account indicators of variation and shape of pressure center distribution, spectral-correlation indicators of stabilograms, as well as integral indicators of stability (length, velocity and angle of postural oscillations) and quality of equilibrium function in two sensory states (open and closed eyes). The obtained data have been calculated in the StabiliS software. Results: In children with non-purulent otitis, the coordinates of the pressure center are (7.04 [2.16 – 10.09]; -1.14 [-28.90 - 9.11]), and in the control group – (7.04 [3.30-16.16]; -13.72 [(-25.17) – (-10.30)]) with eyes closed. The average project ion figure of the pressure center in the sample with closed eyes is actually represented by a circle (ratio of Y / X axes = 0.98 [0.88; 1.14]) in non-purulent otitis media, and in the control group - an ellipse (Y / X axis ratio) = 1.16 [1.01; 1.33]). This indicates the lack of dominance of the ankle strategy to maintain posture in non-purulent otitis in the absence of visual control, and points to the presence of hidden vestibular disorders in non-purulent acute otitis media. Conclusion: The main result of our study is the discovery of the statistically significant decrease in the stability of the main posture and predictability of oscillatory movements in preschool children with acute nonpurulent otitis media compared with the control group only in the absence of visual control, i.e. in closed eyes. Also, statistically significant (p ≤ 0.05) differences have been found between children with acute non-purulent otitis media and control, namely the coefficient of equilibrium function only in the state with closed eyes. Decreased KFR values in children with non-purulent otitis indicate a decrease in the quality of postural control compared to control group. Given the almost asymptomatic nature of otitis media in preschool children, violations of postural control in non-purulent otitis media indicate the presence of latent vestibular disorders, which must be considered for the diagnosis and treatment of otitis media in children.

Motor Strategies Used to Restore Balance in People With and Without Impaired Sensory Organization Suffering From Diabetic Polyneuropathy

Background and Objectives Reduced ability to control balance is one of the disorders affecting the quality of life and daily activities of people with diabetic polyneuropathy (DPN), which can lead to dangerous consequences such as falling. By identifying the causes of balance disorders, we can better understand this condition to provide effective and evidence-based treatments for these patients. This study aims to investigate and compare the use of motor strategies in people with and without impaired sensory organization suffering from DPN. Subjects and Methods In this cross-sectional study, 40 people with DPN participated. Their demographic information were recorded and then underwent balance performance test using the sensory organization test. Based on the results, they were divided into two groups: Control group without impaired sensory organization (n=18) and Patient group with impaired sensory organization (n=22). Results The prevalence of inappropriate use of motor strategies to restore balance in DPN patients with impaired sensory organization was higher than in the control group. The adopted inappropriate strategy was mostly in using ankle strategy, where the somatosensory and visual perturbations were higher. Conclusion Patients with DPN use ankle strategy, instead of hip strategy, to restore balance. This non-use of hip strategy is more common in patients with impaired sensory organization.

Increased trunk movements in people with hereditary spastic paraplegia: do these involve balance correcting strategies?

ObjectiveHereditary spastic paraplegia (HSP) is characterized by a bilaterally spastic gait pattern. During gait, increased trunk movements are often observed. People with HSP likely generate trunk movements to improve foot clearance and step length, but there may be additional explanations. Here, we investigate whether there is an association between reduced balance performance and increased trunk movements, as an increase in trunk movements may partly reflect balance correcting strategies.MethodsWe analyzed an historic cohort of 86 people with HSP who underwent gait analysis and balance examination. Two researchers reviewed gait analyses videos and classified the observed trunk movement as (1) normal, (2) moderately increased, or (3) markedly increased, and categorized participants as ‘toe walkers’ (yes/no). Balance performance and spatiotemporal gait parameters were collected from the medical files. Parameters were compared between people with normal vs. moderately increased trunk movements, moderately vs. markedly increased trunk movements, and normal vs. markedly increased trunk movements.ResultsPatients with moderately increased trunk movements during gait scored lower on the Berg Balance Scale (p = 0.002) and/or the Mini Balance Evaluation Test (p = 0.043) than patients with normal trunk movements. Likewise, patients with markedly increased trunk movements performed worse on the BBS (p = 0.037) and/or the Mini-BESTest (p = 0.004) than patients with moderately increased trunk movements. Patients with markedly increased trunk movements were more often toe walkers than patients with moderately increased (68% vs. 6%; p < 0.001).ConclusionsWe found an association between increased trunk movements and reduced balance capacity. This may have several—not mutually exclusive—explanations. One of these explanations is that trunk movements, at least partly, reflect balance correcting strategies. With the disease progression, ankle strategies and foot placement strategies become impaired and insufficient to restore balance after intrinsic perturbations. Hip strategies are then potentially recruited to maintain balance, resulting in increased trunk movements.

Balance strategy in hoverboard control

This study examines how people learn to perform lower limb control in a novel task with a hoverboard requiring to maintain dynamic balance. We designed an experiment to investigate the learning of hoverboard balance and two control strategies: A hip strategy, which mainly uses hip movements to change the angle of the foot, and an ankle strategy relying more on ankle motion to control the orientation of hoverboard plates controlling the motion. Motor learning was indicated by a significant 10pm 4% decrease in the trial completion time (p < 0.001) and a significant 24 ± 11% decrease in total muscle activation (p < 0.001). Furthermore, the participants, who had no prior experience riding a hoverboard, learned an ankle strategy to maintain their balance and control the hoverboard. This is supported by significantly stronger cross-correlation, phase synchrony, lower dynamic time warping distance between the hoverboard plate orientation controlling hoverboard motion, and the ankle angle when compared to the hip angle. The adopted ankle strategy was found to be robust to the foot orientation despite salient changes in muscle group activation patterns. Comparison with results of an experienced hoverboard rider confirmed that the first-time riders adopted an ankle strategy.

Effect of a controlled starting position on the relationship between the forward reach distance and movement distance of the center of pressure in the functional reach test using the ankle joint strategy.

[Purpose] This study aimed to clarify whether the distribution range of the forward reach distance and the relationship between the forward reach distance and the movement distance of the center of pressure differed depending on whether the controlled starting standing position during the functional reach test with an ankle joint strategy. [Participants and Methods] Sixteen healthy male volunteers participated in the study. The distribution range of the forward reach distance and the relationship between the forward reach distance and movement distance of the center of pressure in the controlled starting standing position and non-controlled starting standing position conditions were analyzed. [Results] The distribution range of the forward reach distance was significantly smaller in the controlled starting standing position than in the non-controlled starting standing position. In both groups, the forward reach distance was associated with the movement distance of the center of pressure. [Conclusion] The findings suggested that the use of an ankle joint strategy with a controlled starting standing position in the functional reach test may be a more accurate method to evaluate standing balance ability.

Characteristics of the stand-to-sit motion in healthy older women : Evaluation of sitting impact by measurement of ground reaction forces.

Objectives : The aims of this study were to examine the biomechanics of StandTS movements in older adults and to identify their optimal StandTS motion by measuring sitting impact forces. Methods : Healthy older women (n = 17) and healthy young women (n = 18) were asked to perform SitTS and StandTS motions at a natural speed using a chair. We measured the ground reaction forces from the participants' feet and the chair, the angle of the trunk and ankle, vertical velocity, and postural muscle activities using a force plate, motion analyzer, and electromyography, respectively. Results : Sitting impact force was significantly greater in the older women than in the young women during the StandTS motion. There was a significant difference between the trunk angle and the ankle angle during the StandTS motion and sitting impact force had a significant negative correlation with the ankle joint motion in the older women. Conclusions : The ankle joint strategy was characterized by body sway resembling a single-segment-inverted pendulum and suggests that this response is less developed in the older adult. These results indicate that the ankle joint strategy may be an important factor involved in the sitting impact force. J. Med. Invest. 69 : 278-286, August, 2022.

Strategic alterations of posture are delayed in Parkinson\u2019s disease patients during deep brain stimulation

Parkinson’s disease (PD) is characterized by rigidity, akinesia, postural instability and tremor. Deep brain stimulation (DBS) of the subthalamic nucleus (STN) reduces tremor but the effects on postural instability are inconsistent. Another component of postural control is the postural strategy, traditionally referred to as the ankle or hip strategy, which is determined by the coupling between the joint motions of the body. We aimed to determine whether DBS STN and vision (eyes open vs. eyes closed) affect the postural strategy in PD in quiet stance or during balance perturbations. Linear motion was recorded from the knee, hip, shoulder and head in 10 patients with idiopathic PD with DBS STN (after withdrawal of other anti-PD medication), 25 younger adult controls and 17 older adult controls. Correlation analyses were performed on anterior–posterior linear motion data to determine the coupling between the four positions measured. All participants were asked to stand for a 30 s period of quiet stance and a 200 s period of calf vibration. The 200 s vibration period was subdivided into four 50 s periods to study adaptation between the first vibration period (30–80 s) and the last vibration period (180–230 s). Movement was recorded in patients with PD with DBS ON and DBS OFF, and all participants were investigated with eyes closed and eyes open. DBS settings were randomized and double-blindly programmed. Patients with PD had greater coupling of the body compared to old and young controls during balance perturbations (p ≤ 0.046). Controls adopted a strategy with greater flexibility, particularly using the knee as a point of pivot, whereas patients with PD adopted an ankle strategy, i.e., they used the ankle as the point of pivot. There was higher flexibility in patients with PD with DBS ON and eyes open compared to DBS OFF and eyes closed (p ≤ 0.011). During balance perturbations, controls quickly adopted a new strategy that they retained throughout the test, but patients with PD were slower to adapt. Patients with PD further increased the coupling between segmental movement during balance perturbations with DBS ON but retained a high level of coupling with DBS OFF throughout balance perturbations. The ankle strategy during balance perturbations in patients with PD was most evident with DBS OFF and eyes closed. The increased coupling with balance perturbations implies a mechanism to reduce complexity at a cost of exerting more energy. Strategic alterations of posture were altered by DBS in patients with PD and were delayed. Our findings therefore show that DBS does not fully compensate for disease-related effects on posture.

Changes in Muscle Strategies During Landing Task in Subjects With and Without Knee Genu Varum

Introduction: Onset and offset activation of lower limb and trunk muscles may change the knee with genu varum during landing. These motor control strategies can be different from those in healthy subjects and contribute to more injuries in lower extremities. This study aimed to compare the delay time of the onset activity of the abdominal and lower limb muscles in the specific landing task. Materials and Methods: Ten females with genu varum deformity and ten females with normal knee participated in this case-control study. Genu varum deformity was measured by a camera capturing goniometer. The subjects were informed to land by preferred lower limb from a table (30 cm high) on a force plate. Vertical Ground Reaction Force (VGRF) was measured to clarify the onset of the landing task. Surface Electromyography (sEMG) of transverse abdominal/int. oblique (TA/IO), Vastus Medialis (VM), Vastus Lateralis (VL), Lateral Gastrocnemius (LG), and medial gastrocnemius (MG) muscles were recorded during landing. The difference between the onset activity of the above muscles and onset of VGRF was calculated as delay times and compared between muscles and between two groups. Also, the offset of activities and the intensity of muscle activation (normalized RMS) were compared between the two groups. Results: Lower limb and trunk muscles showed significantly different onset of activities in the genu varum group (P&lt;0.05), whereas there was no significant difference in the onset of muscle activities in the healthy group. Results indicated significant differences between two groups in TA/IO, LG, and MG muscles and the genu varum group had longer delay time for motor control strategy (especially ankle strategy) in the landing task. Offset time of all muscles in the genu varum and healthy subjects had a significant difference between muscles, especially in gastrocnemius muscles (P&lt;0.05). Also, there were significant changes between the two groups in LG and MG muscles (P&lt;0.05). Normalized muscle activities (nRMS) generally indicated an increase in muscle activation of genu varum subjects (TA/IO, LG, MG) compared with the normal subjects (P&lt;0.05). Conclusion: Motor control strategies in landing task is different in the genu varum group due to changes in biomechanics and properties of the knee joint. This variation may be due to changes in proprioception afferent pathways around the knee joint. An increase in muscle activation, delay, and offset time of muscle activities in these subjects, indicated that an increase in the degree of freedom may change motor control strategies. Internal anticipation and postural adjustment of the landing task in these subjects need more motor unit recruitment (an increase in nRMS). This deformity in the knee joint might affect some activities and possibly cause knee changes such as osteoarthritis.

Ankle muscles drive mediolateral center of pressure control to ensure stable steady state gait

During steady-state walking, mediolateral gait stability can be maintained by controlling the center of pressure (CoP). The CoP modulates the moment of the ground reaction force, which brakes and reverses movement of the center of mass (CoM) towards the lateral border of the base of support. In addition to foot placement, ankle moments serve to control the CoP. We hypothesized that, during steady-state walking, single stance ankle moments establish a CoP shift to correct for errors in foot placement. We expected ankle muscle activity to be associated with this complementary CoP shift. During treadmill walking, full-body kinematics, ground reaction forces and electromyography were recorded in thirty healthy participants. We found a negative relationship between preceding foot placement error and CoP displacement during single stance; steps that were too medial were compensated for by a lateral CoP shift and vice versa, steps that were too lateral were compensated for by a medial CoP shift. Peroneus longus, soleus and tibialis anterior activity correlated with these CoP shifts. As such, we identified an (active) ankle strategy during steady-state walking. As expected, absolute explained CoP variance by foot placement error decreased when walking with shoes constraining ankle moments. Yet, contrary to our expectations that ankle moment control would compensate for constrained foot placement, the absolute explained CoP variance by foot placement error did not increase when foot placement was constrained. We argue that this lack of compensation reflects the interdependent nature of ankle moment and foot placement control. We suggest that single stance ankle moments do not only compensate for preceding foot placement errors, but also assist control of the subsequent foot placement. Foot placement and ankle moment control are ‘caught’ in a circular relationship, in which constraints imposed on one will also influence the other.

Sensory Organization Test Conditions Influence Postural Strategy Rather than Footwear or Workload.

Background: Postural strategies such as ankle, hip, or combined ankle-hip strategies are used to maintain optimal postural stability, which can be influenced by the footwear type and physiological workload. Purpose: This paper reports previously unreported postural strategy scores during the six conditions of the sensory organization test (SOT). Methods: Fourteen healthy males (age: 23.6 ± 1.2 years; height: 181 ± 5.3 cm; mass: 89.2 ± 14.6 kg) were tested for postural strategy adopted during SOT in three types of occupational footwear (steel-toed work boot, tactical work boot, low-top work shoe) every 30 min during a 4-h simulated occupational workload. Postural strategy scores were analyzed using repeated measures analysis of variance at 0.05 alpha level. Results: Significant differences among postural strategy scores were only evident between SOT conditions, and but not between footwear type or the workload. Conclusions: Findings indicate that occupational footwear and occupational workload did not cause a significant change in reliance on postural strategies. The significant changes in postural strategy scores were due to the availability of accurate and/or conflicting sensory feedback during SOT conditions. In SOT conditions where all three types of sensory feedback was available, the ankle strategy was predominantly adopted, while more reliance on hip strategy occurred in conditions with absent or conflicting sensory feedback.

Increase in muscle tone promotes the use of ankle strategies during perturbed stance.

To maintain an upright standing posture against external disturbances, the human body mainly employs two types of postural control strategies: "ankle strategy" and "hip strategy." While it has been reported that the magnitude of the disturbance alters the use of postural control strategies, it has not been elucidated how the level of muscle tone, one of the crucial parameters of bodily function, determines the use of each strategy. We have previously confirmed using forward dynamics simulations of human musculoskeletal models that an increased muscle tone promotes the use of ankle strategies. The objective of the present study was to experimentally evaluate a hypothesis: an increased muscle tone promotes the use of ankle strategies. Do changes in the muscle tone affect the use of ankle strategies? Participants were asked to maintain their standing posture on a movable platform sliding horizontally at several accelerations. Postural reactions for support surface translations were examined under three instructions with or without handgrips: relax state, squeezing a handgrip, and an increased muscle tone of the whole body. Surface-electromyography and marker locations of joints were measured to calculate the index of muscle tone and postural control strategies. The relationship of the indexes was evaluated based on correlation coefficients. In half of the conditions, weak negative correlations were noted between the muscle tone index and postural control strategy index. In other words, an increased muscle tone rather promoted the use of the ankle strategy than the hip strategy. These findings are consistent with our previous simulation results. The results recognized a positive response to the research question. This suggests that it is crucial to take muscle tone into account to understand postural control strategies.

Whole‐Body Multicontact Haptic Human–Humanoid Interaction Based on Leader–Follower Switching: A Robot Dance of the “Box Step”

For physical human–robot interaction (pHRI) where multi‐contacts play a key role, both robustness to achieve robot‐intended motion and adaptability to follow human‐intended motion are fundamental. However, there are tradeoffs during pHRI when their intentions do not match. This paper focuses on bipedal walking control during pHRI, which handles such tradeoff when a human and a humanoid robot having different footsteps locations and durations. To resolve this, a force‐reactive walking controller is proposed by adequately combining ankle and stepping strategies. The ankle strategy maintains the robot's intention based on an analytically‐optimal center of pressure, leading the robot to oppose resistance to multiple contacts from the human. Based on the robot's kinodynamic constraints and/or the confidence of the robot's intention, the stepping strategy updates the robot's footsteps based on the human's intention implied by the multiple contact forces. Consequently, the proposed walking control on pHRI mutually exchanges human–robot intentions in real‐time, thereby achieving coordinated steps. With a full‐sized humanoid robot that is able to detect multi‐contacts in real‐time, we succeeded in performing a long‐term “box‐step” with multi‐contacts pHRI, demonstrating the robustness of our approach.

English

BACKGROUND Falls are very much common in elderly. Fall in geriatric population is one of the common reasons for hospitalization, which may put financial burden on the patient and family. Fall in geriatric population many a times causes fracture and it may lead to serious complications which can threaten life. It may lead to disability and patient may become a handicap. In our study, we identified the correlation between motor strategies of balance control and causes of fall in post-operative elderly individuals. METHODS In this observational study, a total of 100 post-operative elderly individuals who had a fall and who underwent surgery for fracture correction were included. Both males and females in age group of 60 years and above were included. Outcome measures used were balance tests, manual muscle tests and goniometry. RESULTS 28 % individuals had fall due to low level of motor control at ankle joint and 40 % individuals at hip joint. In 16 % of individuals reaching strategy was affected. Suspensory strategy was affected in 10 % of individuals while stepping strategy was affected in 6 % of elderly. Elderly had fall due to weak musculature at hip joint (35 %), knee joint (15 %), ankle joint (30 %) and spine (25 %) irrespective of the individual’s gender. CONCLUSIONS Impairment in motor strategies of balance control such as, hip strategy, stepping strategy, reaching strategy, suspensory strategy, ankle strategy leads to fall in elderly. On the basis of assessment of manual muscle testing (MMT), range of motion and motor strategies of balance control, we concluded that impairment in motor strategies of balance, and reduced joint range of motion lead to falls. KEY WORDS Motor Strategies for Balance Control, Balance Tests, Manual Muscle Testing, Range of Motion

Ankle Muscle Activations during Different Foot-Strike Patterns in Running.

This study analysed the landing performance and muscle activity of athletes in forefoot strike (FFS) and rearfoot strike (RFS) patterns. Ten male college participants were asked to perform two foot strikes patterns, each at a running speed of 6 km/h. Three inertial sensors and five EMG sensors as well as one 24 G accelerometer were synchronised to acquire joint kinematics parameters as well as muscle activation, respectively. In both the FFS and RFS patterns, according to the intraclass correlation coefficient, excellent reliability was found for landing performance and muscle activation. Paired t tests indicated significantly higher ankle plantar flexion in the FFS pattern. Moreover, biceps femoris (BF) and gastrocnemius medialis (GM) activation increased in the pre-stance phase of the FFS compared with that of RFS. The FFS pattern had significantly decreased tibialis anterior (TA) muscle activity compared with the RFS pattern during the pre-stance phase. The results demonstrated that the ankle strategy focused on controlling the foot strike pattern. The influence of the FFS pattern on muscle activity likely indicates that an athlete can increase both BF and GM muscles activity. Altered landing strategy in cases of FFS pattern may contribute both to the running efficiency and muscle activation of the lower extremity. Therefore, neuromuscular training and education are required to enable activation in dynamic running tasks.

Dynamic balance and neuropathic changes following ankle proprioceptive training in type II diabetic patients with peripheral neuropathy

Introduction: Peripheral neuropathy is one of the major complications of type II diabetes mellitus. Lower limb proprioceptive impairments due to neuropathy can lead to balance disorders in these patients. The present study aimed to investigate postural stability and neuropathic changes following ankle proprioceptive training in type II diabetic patients with moderate neuropathy. Materials and Methods: The present study was conducted on 24 type II diabetic patients with moderate neuropathy (9 females and 15 males) aged 40-65 years (with a mean age of 57.25 years). The treatment consisted of ankle proprioceptive training by the balance board and rocker for 10 consecutive days. Balance indices, including Overall Stability Index (OSI), Anterior-Posterior Stability Index (APSI), and Medial-Lateral Stability Index (MLSI), were measured with Biodex system before and after the treatment, as well as two weeks after treatment in two conditions: condition1: Eyes open, head straight, without using trunk, pelvis, thigh, and knee constrained orthosis. Condition 2: Eyes closed, head back (hyperextension), with using trunk, pelvis, thigh, and knee constrained orthosis. Plate-based Biodex stability was fixed at levels 6 and 8 for condition1 and level 8 for condition 2. The severity of neuropathy was assessed using Valk and Michigan questionnaires, as well as light touch sensation. The analysis of variance with repeated measure was used to evaluate alterations in the stability of patients. Furthermore, the correlation of neuropathic changes and stability parameters were assessed by the Pearson correlation coefficients. Results: Significant improvements were observed in OSI in all tests of condition 1 (Biodex Balance System (BBS) at level 8 (P=0.001) and level 6 (P=0.017), as well as test conditions 2 (level 8; P=0.004). After the treatment, at stability level 8, a significant improvement in the mean values of postural sways in the Anterior-Posterior (AP) direction demonstrated that the ankle strategy was improved in the patients. After the treatment, the scores of the Valk (P=0.02) and Michigan (P=0.001) questionnaires were significantly decreased. After two weeks of follow-up, the observed improvement was maintained in the mean values of balance indices (OSI, APSI) and neuropathy due to treatment. Conclusion: As evidenced by the obtained results, 10 sessions of targeted ankle proprioceptive training improved stability, neuropathy, and light touch sensation of the foot in type II diabetic patients with moderate neuropathy. Foot somatosensory information is one of the most important causes of balance alterations in these patients

Understanding the impact of lumbar disc degeneration and chronic low back pain: A cross-sectional electromyographic analysis of postural strategy during predicted and unpredicted postural perturbations

People with chronic low back pain (LBP) exhibit changes in postural control. Stereotypical muscle activations resulting from external perturbations include anticipatory (APAs) and compensatory (CPAs) postural adjustments. The aim and objective of this study was to determine differences in postural control strategies (peak amplitude, APAs and CPAs) between symptomatic and asymptomatic adults with and without Lumbar Disc Degeneration (LDD) using surface electromyography during forward postural perturbation. Ninety-seven subjects participated in the study (mean age 50 years (SD 12)). 3T MRI was used to acquire T2 weighted images (L1-S1). LDD was determined using Pfirrmann grading. A bespoke translational platform was designed to deliver horizontal perturbations in sagittal and frontal planes. Electromyographic activity was analysed bilaterally from 8 trunk and lower limb muscles during four established APA and CPA epochs. A Kruskal-Wallis H test with Bonferroni correction for multiple comparisons was conducted. Four groups were identified: no LDD no pain (n = 19), LDD no pain (n = 38), LDD pain (n = 35) and no LDD pain (n = 5). There were no significant differences in age or gender between groups. The most significant difference between groups was observed during forward perturbation. In the APA and CPA phases of predictable forward perturbation there were significant differences ankle strategy between groups (p = 0.007–0.008); lateral gastrocnemius and tibialis anterior activity was higher in the LDD pain than the LDD no pain group. There were no significant differences in the unpredictable condition (p>0.05). These findings were different from the remaining groups, where significant differences in hip strategy were observed during both perturbation conditions (p = 0.004–0.006). Symptomatic LDD patients exhibit different electromyographic strategies to asymptomatic LDD controls. Future LBP electromyographic research should benefit from considering assessment of both lower limbs in addition to the spine. This approach could prevent underestimation of postural control deficits and guide targeted rehabilitation.

An analysis of postural control strategies in various types of footwear with varying workloads

Footwear and physiological workload have been reported to impact postural stability. Analyses of postural strategies during sensory organisation test (SOT) can aid better understanding of postural control behaviour. The paper reports previously unreported postural strategy scores from each SOT condition, in various types of footwear when exposed to different workloads from two different completed studies. Study 1 analysed postural strategies in alternative footwear [Crocs (CC), flip-flops (FF) and Vibram five-finger (VIB)] before and after a low-intensity workload (n = 18; age: 22.9 ± 2.8 years; height: 179 ± 6.0 cm; mass: 81.3 ± 8.8 kg) and study 2 in military footwear [standard tactical boot (STD) and minimalist tactical boot (MIN)] before and after a high-intensity workload (n = 16; age: 26.63 ± 3.93 years; height: 178.04 ± 6.2 cm; mass: 87 ± 12.4 kg). Findings from the current analyses revealed significant differences in footwear type, workload, and SOT conditions. Design characteristics on alternative footwear and the low intensity workload were not sufficient to cause a significant shift from a predominant ankle to hip strategy. However, design characteristics of STD and the high-intensity workload did cause a shift from an ankle to hip strategy. During SOT conditions where all three types of feedback was readily available (visual, vestibular and somatosensory), an ankle strategy was used to maintain postural stability, while more reliance on hip strategy existed when sensory feedback was absent or in conflict.