Hip Strategy Research Articles

The effect of trunk exercises with hip strategy training to maximize independence level and balance for patient with stroke: Randomized controlled study.

Balance while seated and the capacity to conduct selective trunk movements are significant predictors of functional outcomes following stroke. Patients with inappropriate muscle activation and inadequate movement control in the trunk muscles cause mobility and daily function difficulties. Stroke patients have weak leg muscles and decreased balance, resulting in compensatory changes. Functional postural strategy training is necessary to restore balance in these patients. Few studies have examined the effect of physical therapy trunk exercises with hip strategy training on improving balance and increasing independence after stroke. This study aimed to explore the effect of selective trunk exercises (STE) with hip strategy training in improving balance in patients with stroke as well as independence levels. A multicenter inpatient stroke treatment randomized pre- and post-test control trial. Forty-six stroke survivors were randomly allocated to experimental or control groups (n=23 each). The experimental group received hip strategy training and trunk exercises. All groups received Neuro-Developmental Treatment (NDT)-based physical therapy four times a week for 6weeks. Trunk impairment scale, Berg Balance Scale (BBS), and functional independence measure (FIM) measured static and dynamic seated balance, functional balance, and trunk movement coordination pre- and post-therapy. The experimental group's post-therapeutic measures were substantially higher than the control group. The experimental group's TIS score, and subscale improved more than the control group. The experimental group considerably increased the BBS score. The experimental group also showed greater FIM gains. This study demonstrated that adding STE in conjunction with hip strategy training to patients after has a positive impact on trunk control while maintaining static and dynamic sitting balance, functional balance, and independence levels which are effective in stroke rehabilitation.

Acute Effects of Combined Hypoxia and Fatigue on Balance in Young Men

The aim of this study was to determine the effects of maximal exercise and maximal exercise under hypoxic conditions on balance, the strategies of the balance-maintenance process and its sensory organization. A total of 60 men were randomly allocated to three experimental groups and a control group. All participants completed the sensory organization test for assessing balance. Participants in the experimental groups performed the same test after an hour of normobaric hypoxia (the first group), after supramaximal exercise (the second group) and after supramaximal exercise combined with 60 min of hypoxia exposure (the third group). The control group performed the test after 60 min of passive rest. Normobaric hypoxia conditions corresponded to an altitude of 2950 m (FIO2 15%). Physical effort in normoxia and hypoxia significantly impaired the participants’ stability on a stable platform with eyes open (η2 = 0.711, p = 0.001; η2 = 0.583, p = 0.001, respectively). On an unstable platform, a significant improvement in stability indices was observed in the group undertaking the exercise in hypoxia (p = 0.04, η2 = 0.249). The experimental conditions increased the role of hip strategies in maintaining balance in the experimental groups during trials requiring somatosensory information. An analysis of sensory organization shows that maximal effort in hypoxia increases the role of somatosensory (p = 0.002, η2 = 0.69) and vestibular (p = 0.02, η2 = 0.34) information, whereas hypoxia alone increases reliance on visual (p = 0.03, η2 = 0.38) and vestibular (p = 0.02, η2 = 0.36) information. This study indicates that individuals have poorer stability after maximal exercise, which may cause difficulties in engaging in some dynamic forms of activity, especially those with a large number of visual stimuli.

A Passive Polycentric Mechanism to Improve Active Mediolateral Balance in Prosthetic Walking.

Prosthetic legs are typically passive systems without active ankle control, restricting mediolateral balancing to a hip strategy. Resulting balance control impairments for persons with a lower extremity amputation may be mitigated by increasing hip strategy effectiveness, in which relatively small hip moments of force are adequate for mediolateral balancing. To increase hip strategy effectiveness we have developed a prosthetic leg prototype based on the Peaucellier mechanism, the Sideways Balance Mechanism (SBM). This polycentric mechanism adds a frontal plane degree of freedom, reducing mediolateral body displacements. Adding a passive joint alone introduces instability, in which mediolateral body rotation leads to CoM height loss, ultimately resulting in a fall. The SBM however provides stability typically absent by lengthening under rotation, thereby compensating for CoM height loss. By allowing for both foot rotation (in-/eversion), and increased mediolateral ground reaction force the SBM increases hip strategy effectiveness. We aimed to provide proof of principle that the SBM can improve active mediolateral balance control in prosthetic walking by increasing hip strategy effectiveness compared to a typical set-up. Comparison between a typical set-up and the SBM showed an increased mediolateral ground reaction force at equal hip moments of force for a 2D forwards dynamics computer simulation, and a reduced hip moment of force at equal mediolateral ground reaction force for a case study. Results validate increased hip strategy effectiveness of the SBM compared to a typical set-up, providing proof of principle that adding an SBM to a prosthetic set-up improves mediolateral balance control in prosthetic walking.

Coordination of hip and spine in individuals with acute low back pain during unstable sitting

BACKGROUND CONTEXTTrunk postural control differs between individuals with and without chronic low back pain. Whether this corresponds to differences in hip/spine coordination during the early acute phase of LBP (ALBP) is unclear. PURPOSETo compare hip/spine coordination in relation to seat movements between individuals with and without ALBP when balancing on an unstable seat and to identify coordination strategies to maintain balance using cluster analysis. STUDY DESIGN/SETTINGCross-sectional observational study. PATIENT SAMPLEALBP (n=130) and pain-free (n=72) individuals. OUTCOME MEASURESFrequency domain measures to evaluate hip/spine coordination (amplitude spectrum, phase angle, coherence) and time-series measures to assess overall balance performance (centre of pressure [CoP] reflecting the amount of seat movements, upper thorax motion as a surrogate for head motion). METHODSParticipants maintained balance while sitting on a seat fixed to a hemisphere. Seat, hip and spine (lower lumbar, lumbar, upper lumbar, thoracic) angular motion and force plate data were recorded. RESULTSOverall, seat/CoP movements (amplitude spectrum and RMSdisplacement) were greater (in both planes) and sagittal coordination (coherence) between the hip or lower spine and seat movements was lower in ALBP than controls. Cluster analysis using coherence data revealed different coordination strategies to maintain balance. Separate clusters used a “lower lumbar strategy” and “hip strategy” in the sagittal plane, and a “lower and upper lumbar strategy” and “lower lumbar strategy” in the frontal plane. A cluster using a “low coherence strategy” in both planes was also identified. CONCLUSIONSHip and lower spine coordination was less in individuals with ALBP in conjunction with a lower quality of overall balance performance. However, interpretation of the relationship between coherence and overall balance performance was not straightforward. Clusters in both the ALBP group and the control group adopted a low coherence strategy, and this was not consistently related to poor overall balance performance. This suggests overall balance performance cannot be inferred from coherence alone and requires consideration of interaction of other different features.

Training Postural Balance Control with Pelvic Force Field at the Boundary of Stability.

This study characterizes the effects of a postural training program on balance and muscle control strategies in a virtual reality (VR) environment. The Robotic Upright Stand Trainer (RobUST), which applies perturbative forces on the trunk and assistive forces on the pelvis, was used to deliver perturbation-based balance training (PBT) in a sample of 10 healthy participants. The VR task consisted of catching, aiming, and throwing a ball at a target. All participants received trunk perturbations during the VR task with forces tailored to the participant's maximum tolerance. A subgroup of these participants additionally received assistive forces at the pelvis during training. Postural kinematics were calculated before and after RobUST training, including (i) maximum perturbation force tolerated, (ii) center of pressure (COP) and pelvic excursions, (iii) postural muscle activations (EMG), and (iv) postural control strategies (the ankle and hip strategies). We observed an improvement in the maximum perturbation force and postural stability area in both groups and decreases in muscle activity. The behavior of the two groups differed for perturbations in the posterior direction where the unassisted group moved towards greater use of the hip strategy. In addition, the assisted group changed towards a lower margin of stability and higher pelvic excursion. We show that training with force assistance leads to a reactive balance strategy that permits pelvic excursion but that is efficient at restoring balance from displaced positions while training without assistance leads to reactive balance strategies that restrain pelvic excursion. Patient populations can benefit from a platform that encourages greater use of their range of motion.

Three Hertz postural leg tremor impairs posture maintenance in multiple system atrophy-cerebellar type.

Three-Hz postural leg tremor has recently been identified as highly prevalent in patients with the cerebellar type of multiple system atrophy, but its impact on posture maintenance remains poorly understood. Thirty-seven patients with spinocerebellar ataxia and 58 others with cerebellar type of multiple system atrophy were given Synapsys posturography examinations. Fifty-three healthy controls were also tested. Low, medium, and high-frequency sway were recorded to compute energy values. Frequency shift and postural strategy predominance were evaluated from the postural sway distributions, mainly from the proportions of higher frequency values among the total values. The trajectories of postural sway components were evaluated with the generalized additive mixed model. Distributions of the components and their relationships with falls and tremors were assessed through repeated measures correlation analysis. As the test difficulty increased, the standard controls showed slight increases in the energy values at every frequency. Distributions of the higher frequency (>0.5 Hz) values increased escalatingly with test difficulty, illustrating frequency shifts and hip strategy predominance. Medium and high-frequency values were strongly and positively inter-correlated in normal stances, but this was not observed among the spinocerebellar ataxia or multiple system atrophy patients. Unlike normal stances, the proportion of medium frequency values was negatively related to the total value among the spinocerebellar ataxia and multiple system atrophy patients, implying a failure of frequency shift in response to perturbation. Medium frequency proportions were also inversely correlated with tremors among the multiple system atrophy patients. The observed synchronized changes in medium and high-frequency postural sway indicate that they constitute a complete hip strategy for posture control. The strategy was rigid in those with spinocerebellar ataxia but completely disrupted in those with multiple system atrophy. Three Hertz postural leg tremors destabilize the ankle joints and interfere with postural adjustment among those with multiple system atrophy.

Proprioceptive reliance on trunk muscles for maintaining postural stability decreases in older patients with sagittal imbalance

BackgroundControl of postural adjustments requires tight regulation of the spinal alignments. Sagittal imbalance may cause balance impairment and proprioceptive decline in older adults. However, the evidence on the proprioceptive mechanisms is limited, although it is known that poor proprioceptive inputs may induce spinal deformities. Thus, this study aimed to measure proprioceptive control quantifiers in older adults with sagittal imbalance to clarify the characteristic postural adjustments during proprioceptive inputs. Research questionWhat are the specific proprioceptive postural adjustments required to maintain balance in older adult patients with lumbar spondylosis? MethodsThis was a cross-sectional, observational study. The participants were classified according to the sagittal vertical axis (SVA) lengths with 50 mm as the cut-off value. The pressure displacement center was determined in 36 patients without sagittal imbalance and 68 patients with sagittal imbalance during an upright stance on a balance board with eyes closed. Vibratory stimulations of 27–272 Hz were applied to the gastrocnemius (GS) and lumbar multifidus (LM) muscles to measure the relative contributions and center of pressures of different relative proprioceptive weighting ratios (RPWs) used on postural adjustments. ResultsThe RPWs of older adults with sagittal imbalance were higher than that in those without sagittal imbalance (56–100 Hz; p = 0.013). Logistic regression analysis showed that older patients with sagittal imbalance had a significant ankle proprioception control of advantage (odds ratio: 1.1, 95% confidence interval: 1.01−1.1, p = 0.012). SignificanceIn older patients with sagittal imbalance, the reliance on hip strategy during balance control (RPW 56–100 Hz) decreases. A quantitative assessment of postural stability during proprioceptive inputs is crucial to identify dependence on proprioception signals, including postural strategy, in older patients with sagittal imbalance. Interventions to improve proprioception can improve the postural stability and strategy of older patients with sagittal imbalance.

The Effect of the Postural Control Strategy on the Recognition Error of Center-of-Pressure Sway

The purpose of this study was to examine the effect of postural control strategies on the recognition error (RE) of center-of-pressure (COP) sway forward based on perceived exertion. Participants were 43 middle-aged or elderly people. We measured the maximum COP sway forward (100% center-of-pressure distance(COP-D)), 60% and 30% COP-D of 100% COP-D based on perceived exertion, and participants were classified into the good balance group and bad balance group by RE. The RE and trunk and leg angles were evaluated during COP sway forward. Results showed that RE being significantly higher for 30% COP-D and the group with a larger RE had a significantly larger trunk angle. Therefore, they may have used hip strategy predominantly to perform postural control ability, not only maximum values, but also on perceived exertion.

Sensory Organization and Postural Control Strategies in Individuals With Mild and Moderate-to-Severe Forward Head Posture: A Comparative Study

ObjectiveThis study aimed to compare sensory organization test and postural control strategies between individuals with mild and moderate-to-severe forward head posture (FHP). MethodsA sensory organization test (SOT) was performed in 6 conditions using computerized dynamic posturography, to assess postural control. Equilibrium scores representing overall balance, strategy analysis to assess ankle vs hip strategy dominance, and sensory analysis (Somatosensory, visual, vestibular, visual preference ratio) as an indicator of the use of sensory systems were obtained. ResultsOur results revealed a significant difference between the 2 groups in terms of equilibrium score (P < .05) and strategy scores (P < .05) in conditions of 4 to 6 of the SOT. The results of sensory analysis of SOT showed visual and vestibular ratios were significantly different between the 2 study groups (P < .05), but somatosensory and visual preference ratios were not significantly different between these 2 groups (P > .05). ConclusionIndividuals with moderate-to-severe FHP swayed more in comparison with mild FHP ones in conditions with the Sway-referenced platform of the SOT. They tended to rely on the hip strategy more than the ankle strategy excessively when sensory difficulty increased. Overall, it can be concluded that individuals with moderate-to-severe FHP are more likely to have postural deficits.

Sensory organization of postural control after long term space flight.

Alterations in motor control systems is an inevitable consequence of space flights of any duration. After the flight, the crew-members have significant difficulties with maintaining upright balance and locomotion, which last several days following landing. At the same time, the specific mechanisms of these effects remain unclear. The aim of the study was to assess effects of long-term space flight on postural control and to define the changes of sensory organization caused by microgravity. 33 cosmonauts of Russian Space Agency, the members of International Space Station (ISS) flights of duration between 166 and 196 days took part in this study. Computerized Dynamic Posturography (CDP) tests, which include assessment of visual, proprioceptive and vestibular function in postural stability, was performed twice before the flight and on the 3rd, 7th, and 10th days after landing. The video analysis of ankle and hip joints fluctuations was performed to investigate the basis of postural changes. Exposure to long-term space flight was followed by considerable changes of postural stability (-27% of Equilibrium Score value in the most complicated test, SOT5m). Changes in postural strategies to maintain balance were observed in the tests which provide the challenge for vestibular system. In particular, increased hip joint involvement (+100% in median value and +135% in 3rd quartile of hip angle fluctuation RMS in SOT5m) into postural control process was revealed. Decrease of postural stability after long-term space flight was associated with alterations in vestibular system and biomechanically was revealed by increased hip strategy which is less accurate, but simpler in terms of the central control.

Center of Pressure Deviation during Posture Transition in Athletes with Chronic Ankle Instability.

Center of pressure (COP) tracking during posture transition is an ideal scale for determining the recurrence of an ankle injury, thereby preventing chronic ankle instability (CAI). However, the same is difficult to determine because the reduced ability of certain patients (who experienced sprain) to control posture at the ankle joint is masked by the chain of hip and ankle joint motion. Thus, we observed the effects of knee joint immobilization/non-immobilization on postural control strategies during the posture transition task and attempted to evaluate the detailed pathophysiology of CAI. Ten athletes with unilateral CAI were selected. To examine differences in COP trajectories in the CAI side and non-CAI legs, patients stood on both legs for 10 s and one leg for 20 s with/without knee braces. COP acceleration during the transition was significantly higher in the CAI group with a knee brace. The COP transition from the double- to single-leg stance phase was significantly longer in the CAI foot. In the CAI group, the fixation of the knee joint increased COP acceleration during postural deviation. This suggests that there is likely an ankle joint dysfunction in the CAI group that is masked by the hip strategy.

Joint torque parameters of lower limbs and the relationship with postural balance in young adults: a cross-sectional study

BACKGROUND: Different factors can influence the performance of postural control (PC), one of them being muscle function, which emerges as the neuromuscular capacity to generate tension adaptable to postural disturbances in the lower limbs. AIM: To investigate the influence of joint torque parameters of the lower limbs (hip, knee, and ankle) on the variables of postural balance, analyzed by static posturography in young adults. METHOD: This study included 25 young adults (23.08 ± 4.44 years) who were submitted to motor tasks alternating: the base of support; the surface and vision conditions on a force plate. Joint torque was measured using an isokinetic dynamometer. RESULTS: The hip-abduction, -adduction, and -extension torques were negatively associated with the variables of center of pressure displacement in several conditions, both the most challenging and the least challenging ones. The ankle torque (dorsiflexion and plantar flexion) was negatively associated with postural control only in the semi-tandem condition with a rigid surface and eyes open. On the other hand, the knee torque was positively associated with the center of pressure displacement. Power measurements were more associated with postural control than peak torque. CONCLUSION: In young adults, there seems to be a greater use of the hip strategy, with greater influence of hip torque in relation to ankle torque for postural balance control. Therefore, the strengthening of hip muscles could have an impact on postural control in young adults.

Adaptation to repeated standing-slips in professional ballet dancers

Ballet training is being increasingly used to improve physical functions in older adults. Our previous work showed that ballet dancers react to a novel standing-slip more effectively than their non-dancer counterparts through better control of the recovery step and trunk movement. The purpose of this study was to test if and to what extent ballet dancers adapt differently to repeated standing-slips relative to non-dancers. Protected by a harness, twenty young adults (10 professional ballet dancers and 10 age/sex-matched non-dancers) experienced five repeated and standardized standing-slips on a treadmill. Changes from the first slip (S1) to the fifth slip (S5) in dynamic gait stability (primary outcome) and other variables, including the center of mass position and velocity, step latency, slip distance, ankle angle, and trunk angle (secondary outcomes) were compared between groups. Results revealed that both groups adopted similar proactive controls to improve dynamic gait stability by using the ankle and hip strategies. However, dancers showed a better reactive improvement in stability after the repeated slips than non-dancers. From S1 to S5, dancers reactively improved their dynamic gait stability more than non-dancers at the recovery step liftoff (p = 0.003). Dancers decreased their recovery step latency (p = 0.004) and shortened the slip distance (p = 0.004) significantly more than non-dancers from S1 to S5. These findings suggest that ballet dancers could facilitate the adaptation to repeated slips, which may be attributed to their ballet practice experience. This finding augments our understanding of the underlying mechanisms of ballet practice reducing falls.

Human Sway on a Balance Platform

In the body balance process control, a variety of postural strategies for balance recovery are used. Postural strategies are automatic stable muscular patterns. Such a mechanism reduces the degrees of freedom number, simplifies, speeds up the posture adjustment, and minimizes energy expenditure. They relate to the existence of some motor coordination sets and describe three mobility strategies: ankle, hip, and step strategy. The hip strategy occurs when interference is greater or the use of the ankle strategy is impossible, for example, due to the delay of the postural information cycle. From a dynamical systems point of view, a human attempting to balance upright on an unstable balance board represents the coupling of two dynamical systems, the human balance system with neuromuscular feedback supported on the balance board (an inverted pendulum). The coupling of these two dynamical systems, with time delay and nonlinearities, creates an ideal setting for the emergence of complex postural behaviour and unanticipated interactions between the individual, task, and the external dynamical system. The article presents an analysis of the pendulums concerning the issue of maintaining balance by man.

Effect of Load Carriage Lifestyle on Kinematics and Kinetics of Gait.

Backpacks are commonly worn by many people for multiple purposes. This study investigated the effects of habitual wearing of backpacks on lower limb kinematics and kinetics. Fourteen participants were recruited for analysis. All participants performed four randomly assigned scenarios, including running and walking at speeds of 3.5 and 1.5 m/s, respectively, with and without load carriage. The motion analysis system and force plate were used to investigate the lower limb kinematics and kinetics. A paired sample t-test was performed for statistical measurement with a significance level of α = .05. The results indicated that active force, breaking force, impact peak, loading rate, active peak, maximum braking, hip flexion, and hip range of motion were substantially higher under load carriage conditions than under walking condition, however, time to peak was lower. Conversely, during load carriage running, active force, braking impulse, time to peak, ankle plantarflexion, and ankle range of motion were all higher than those during running. Carrying a backpack weighing 10% of the body weight induced different foot strike patterns at both speeds; during load carriage walking, the hip tended to flex more; whereas, during load carriage running, the ankle tended to flex more. In conclusion, human body seems to adopt different gait strategies during load carriage walking and running. That is, the hip strategy is used during walking, while the ankle strategy is used during running.

Synergistically enhanced strength and ductility of TiB/(TA15-Si) composites: A two-step HIP strategy

A novel two-step hot isostatic pressing strategy has been brought up to fabricate a kind of TiB/(TA15-Si) composites. The densification process and the process of introducing TiB reinforcement by in-situ synthesized reaction were separated. As a result, a network distribution of TiB reinforcement was achieved, and a bimodal matrix grain structure was regulated. By comparing the mechanical properties of the composites fabricated by traditional hot isostatic pressing method, we found that this novel strategy enhanced the yield strength and ultimate tensile strength by 9.6% and 11.0%, respectively. Moreover, the elongation was also improved from 4.7% to 6.6%. Through theoretical calculation and quasi-in-situ characterization, the strength enhancement was determined to be contributed by grain boundary strengthening, and the ductility was benefited by the bimodal structure of titanium matrix.

Development of a New Robust Stable Walking Algorithm for a Humanoid Robot Using Deep Reinforcement Learning with Multi-Sensor Data Fusion

The difficult task of creating reliable mobility for humanoid robots has been studied for decades. Even though several different walking strategies have been put forth and walking performance has substantially increased, stability still needs to catch up to expectations. Applications for Reinforcement Learning (RL) techniques are constrained by low convergence and ineffective training. This paper develops a new robust and efficient framework based on the Robotis-OP2 humanoid robot combined with a typical trajectory-generating controller and Deep Reinforcement Learning (DRL) to overcome these limitations. This framework consists of optimizing the walking trajectory parameters and posture balancing system. Multi-sensors of the robot are used for parameter optimization. Walking parameters are optimized using the Dueling Double Deep Q Network (D3QN), one of the DRL algorithms, in the Webots simulator. The hip strategy is adopted for the posture balancing system. Experimental studies are carried out in both simulation and real environments with the proposed framework and Robotis-OP2’s walking algorithm. Experimental results show that the robot performs more stable walking with the proposed framework than Robotis-OP2’s walking algorithm. It is thought that the proposed framework will be beneficial for researchers studying in the field of humanoid robot locomotion.

Balance impairment in cerebrotendinous xanthomatosis: Ankle strategy deficit. A case study

BackgroundCerebrotendinous xanthomatosis is a rare autosomal-recessive lipid storage disorder causing an elevation in cholestanol and cholesterol levels and their deposition in the central nervous system and tendons with consequent posture and gait disturbances. MethodsThis report shows the case of a 36-year-old male affected by Cerebrotendinous xanthomatosis with static and dynamic instability. We aimed to provide an instrumented quantification of quiet upright standing using a piezoelectric force platform measuring the variations of center of pressure with the foot position 10 cm and 20 cm apart or extra-rotated with an opening angle of 30°, with eyes open or closed. The area of center of pressure and the length of its trajectory in the anterior-posterior and medial-lateral directions were computed. The temporal variability of center of pressure was evaluated by means of the Root Mean Square. FindingsIn comparison with a control group, the area, the trajectory length of center of pressure in anterior-posterior and medial-lateral directions and the temporal variability increased in all static conditions. Intra-patient comparison showed that foot position 10 cm apart was the position that most influenced stability causing a marked worsening of area and trajectory length of center of pressure in both anterior-posterior and medial-lateral directions, particularly for the eyes closed condition. InterpretationWe found a large static instability due to internal neural and biomechanical constraints causing an insufficiency of ankle strategy. A physical therapy program based on instrumented proprioceptive exercises is to be implemented to teach the use of a hip strategy.

Balance Recovery Strategy in Children With and Without Hearing or Visual Impairments.

The purpose of this study was to examine the balance recovery strategy in children with hearing (HI) and visual impairments (VI) compared with those without these disorders. This study featured a cross-sectional design with subjects (N = 45) placed within one of three equally stratified purposive groups (HI, VI, and comparison) within the age range of 9-13years (mean = 11.43, SD = 1.5). Balance recovery strategy was measured in static and after-perturbation conditions by a four-camera Vicon system used to record three-dimensional lower body kinematic data. A repeated-measures analysis of variance (3 × 2, Group × Condition) was utilized to analyze data. Significance was set at p ≤ .05. In the static condition, the results of the study showed that there was no significant difference between the groups in the ankle joint sway (p > .05). In hip joint sway, VI children had greater sway compared with comparison (p = .001) and HI children (p = .02). Also, HI children had greater sways than comparison (p = .02). In the after-perturbation condition, the results showed that VI children had greater sway in the hip and ankle joints than HI children (p = .001) and comparison (p = .001) to restore and maintain balance. It seems that comparison as well as higher proportion VI children use a hip strategy to maintain and restore balance. Also, it seems that HI children use a different strategy (ankle strategy) to maintain and restore balance compared with comparison and VI children.

Effects of visual deprivation on the injury of lower extremities among functional ankle instability patients during drop landing: A kinetics perspective.

Background: The ankle is prone to injury during drop landing with usual residual symptoms, and functional ankle instability (FAI) is the most common. Vision guarantees the postural stability of patients with FAI, and visual deprivation (VD) increases their risk of injury when completing various movements. This study explored injury risk during drop landing in patients with FAI under VD through the kinetics of lower extremities. Methods: A total of 12 males with FAI participated in the study (age, 23.0 ± 0.8years; height, 1.68 ± 0.06m; weight, and 62.2 ± 10.4kg) completed single-leg drop landings under visual presence (VP) and VD conditions. Ground reaction force (GRF), time to peak GRF, joint torque, and vertical length variation (ΔL) were measured. Results: Significant effects were detected in the group for time to peak lateral GRF (p = 0.004), hip extensor torque (p = 0.022), ankle plantarflexion torque (p < 0.001), ankle varus torque (p = 0.021), lower extremity stiffness (p = 0.035), and ankle stiffness (p < 0.001). Significant effects of conditions were detected for vertical GRF, time to peak vertical and lateral GRF, loading rate, hip extensor torque, knee extensor torque, hip varus torque, knee varus torque, lower extremity stiffness, and ankle stiffness (p < 0.05). ΔL was affected by VD with a significant difference (p < 0.001). Conclusion: In patients with FAI, an unstable extremity has a higher injury risk than a stable extremity, and VD increases such risk. However, because the influence of the central nervous system on hip strategy is also affected, the effect on the unstable extremity is more significant and more likely to result in injury. Deepening the squat range may be an effective preventive measure for reducing injury risk of unstable extremities during drop landing.