Hip Strategy Research Articles

Hip Strategy During Landing Reduces Knee Abduction Moment In Collegiate Soccer Players

Hip Strategy During Landing Reduces Knee Abduction Moment In Collegiate Soccer Players

Postural strategies assessed with inertial sensors in healthy and parkinsonian subjects

The present study introduces a novel instrumented method to characterize postural movement strategies to maintain balance during stance (ankle and hip strategy), by means of inertial sensors, positioned on the legs and on the trunk.We evaluated postural strategies in subjects with 2 types of Parkinsonism: idiopathic Parkinson's disease (PD) and Progressive Supranuclear Palsy (PSP), and in age-matched control subjects standing under perturbed conditions implemented by the Sensory Organization Test (SOT). Coordination between the upper and lower segments of the body during postural sway was measured using a covariance index over time, by a sliding-window algorithm. Afterwards, a postural strategy index was computed. We also measured the amount of postural sway, as adjunctive information to characterize balance, by the root mean square of the horizontal trunk acceleration signal (RMS). Resultsshowed that control subjects were able to change their postural strategy, whilst PSP and PD subjects persisted in use of an ankle strategy in all conditions. PD subjects had RMS values similar to control subjects even without changing postural strategy appropriately, whereas PSP subjects showed much larger RMS values than controls, resulting in several falls during the most challenging SOT conditions (5 and 6). Results are in accordance with the corresponding clinical literature describing postural behavior in the same kind of subjects.The proposed strategy index, based on the use of inertial sensors on the upper and lower body segments, is a promising and unobtrusive tool to characterize postural strategies performed to attain balance.

A bidirectional model of postural sway using force plate data.

This work was designed to expand on our previous anterior-posterior postural control model to include medial-lateral sway of unperturbed posture during quiet standing. The bidirectional model simulates two decoupled inverted pendulums, each restricted to sway in either the anterior-posterior (AP) direction (ankle strategy) or medial-lateral (ML) direction (hip strategy), and each controlled by a Proportional-Integral-Derivative (PID) controller. Postural data was collected from 31 healthy participants under different sensory test conditions: eyes closed, eyes open, and eyes open with real-time visual feedback. Simulation iterations of the bidirectional model were run for each sensory test condition to adjust the PID controller parameters until modeled sway metrics did not differ significantly from experimental metrics at p ≤ 0.01. Simulations did not show significant changes in the AP sway controller parameters among the 3 sensory test conditions. The model did show significant changes in ML sway controller parameters, namely stiffness and time delay. Significant differences were also seen in the experimental sway metrics under the three different sensory test conditions. The multi-sensory evaluation and bidirectional sway model offer unique insight for further exploration of postural pathology, control mechanisms and planar coupling that includes both ankle and hip strategies.

Postural tasks are associated with center of pressure spatial patterns of three-dimensional statokinesigrams in young and elderly healthy subjects

The present study investigated the association between postural tasks and center of pressure spatial patterns of three-dimensional statokinesigrams. Young (n=35; 27.0±7.7years) and elderly (n=38; 67.3±8.7years) healthy volunteers maintained an undisturbed standing position during postural tasks characterized by combined sensory (vision/no vision) and biomechanical challenges (feet apart/together). A method for the analysis of three-dimensional statokinesigrams based on nonparametric statistics and image-processing analysis was employed. Four patterns of spatial distribution were derived from ankle and hip strategies according to the quantity (single; double; multi) and location (anteroposterior; mediolateral) of high-density regions on three-dimensional statokinesigrams. Significant associations between postural task and spatial pattern were observed (young: gamma=0.548, p<.001; elderly: gamma=0.582, p<.001). Robustness analysis revealed small changes related to parameter choices for histogram processing. MANOVA revealed multivariate main effects for postural task [Wilks’ Lambda=0.245, p<.001] and age [Wilks’ Lambda=0.308, p<.001], with interaction [Wilks’ Lambda=0.732, p<.001]. The quantity of high-density regions was positively correlated to stabilogram and statokinesigram variables (p<.05 or lower). In conclusion, postural tasks are associated with center of pressure spatial patterns and are similar in young and elderly healthy volunteers. Single-centered patterns reflected more stable postural conditions and were more frequent with complete visual input and a wide base of support.

Ankle Joint Stiffness and Damping Pattern under Different Frequency of Translation Perturbation

The change of effective stiffness and damping characteristic of ankle joint are able to indicate degeneration of balance ability due to ageing effect. This paper will discuss the ankle joint stiffness and damping pattern along repeated translation perturbation. Six young healthy subjects were exposed to five trials of five different frequencies of perturbation (quiet standing, 0.2 Hz, 0.4 Hz, 0.6 Hz and 0.8 Hz). The result showed that the mean of effective stiffness was reduced with the increase of frequency applied; meanwhile the mean of damping value increased with increasing frequency. Additionally, a cubic polynomial curve (u-shape) was estimated to represent stiffness pattern when using curve fitting method with correlation R2&gt;0.5. These estimations also suggested that ankle joint does not oscillate like spring-damper system which is based on inverted pendulum model; however, it applied a different strategy to maintain balance, in particular during initiation, middle and termination of perturbation. These also indicate the influence of sensory processing and adaptation to maintain balance under a long period of disturbance. On the other hand, damping pattern seems to be similar over different frequencies and under repeated perturbation. Besides, the change of stiffness pattern at higher frequency of perturbation (0.8 Hz) recommends the change in posture strategy from ankle to hip strategy. These findings indicated that stiffness and damping are able to describe adaptation of human posture strategy to keep balance and motor learning under repeated perturbation.

Slowed muscle force production and sensory organization deficits contribute to altered postural control strategies in children with developmental coordination disorder

This study aimed to (1) compare the postural control strategies, sensory organization of balance control, and lower limb muscle performance of children with and without developmental coordination disorder (DCD) and (2) determine the association between postural control strategies, sensory organization parameters and knee muscle performance indices among children with DCD. Fifty-eight DCD-affected children and 46 typically developing children participated in the study. Postural control strategies and sensory organization were evaluated with the sensory organization test (SOT). Knee muscle strength and time to produce maximum muscle torque (at 180°/s) were assessed using an isokinetic machine. Analysis of variance was used to compare the outcome variables between groups, and multiple regression analysis was used to examine the relationships between postural control strategies, sensory organization parameters, and isokinetic indices in children with DCD. The DCD group had significantly lower strategy scores (SOT conditions 5 and 6), lower visual and vestibular ratios, and took a longer time to reach peak torque in the knee flexor muscles than the control group (p>0.05). After accounting for age, sex, and body mass index, the vestibular ratio explained 35.8% of the variance in the strategy score of SOT condition 5 (p<0.05). Moreover, the visual ratio, vestibular ratio, and time to peak torque of the knee flexors were all significant predictors (p<0.05) of the strategy score during SOT condition 6, accounting for 14, 19.7, and 19.8% of its variance, respectively. The children with DCD demonstrated deficits in postural control strategy, sensory organization and prolonged duration of muscle force development. Slowed knee muscle force production combined with poor visual and vestibular functioning may result in greater use of hip strategy by children with DCD in sensory challenging environments.

AB0876 Postural profile in patients with ankylosing spondylitis: Correlation with clinical and electrophysiological findings

BackgroundCompromised balance in ankylosing spondylitis (AS) is mostly related to poor posture. Other possibly implicated contributers to poor balance are joint pains and cord pathology. There are few studies in...

Risk of fall for people with diabetes

Purpose: To examine the risk of fall for people with diabetes compared with healthy control subjects. Correlation between tactile sensation and postural control was examined for subjects with diabetes. Methods: Subjects with type 2 diabetes were classified into two groups: (i) diabetes without neuropathy (n = 23) and (ii) diabetic peripheral neuropathy (DPN) (n = 9). Age-matched healthy control subjects (n = 32) were recruited. Tactile sensation, equilibrium scores (ES), strategy scores and sensory analysis scores from the Sensory Organization Test (SOT) were compared among the groups. Results: Subjects with diabetes without neuropathy demonstrated impaired postural control upon the disruption of somatosensory inputs. Subjects with DPN lost balance upon being deprived of visual inputs. A decrease in tactile sensation was associated with a decrease in the ESs in all subjects with diabetes (r = −0.35 to −0.77; p < 0.05), and they tend to use more hip strategy for postural control upon being deprived of visual inputs. Conclusions: Different postural control strategies are adopted by various subgroups of subjects with diabetes. Subjects with DPN demonstrated a significant shift from ankle to hip strategies for balance tests when vision was deprived.Implications for RehabilitationThe severity of diabetic peripheral neuropathy (DPN) is associated with the risk of fall.Different compensatory strategies in balance control have been adopted by different subgroups of people with diabetes.In order to minimize the risk of fall, specific balance training program should be offered to different subgroups of people with diabetes.The balance training should emphasize on optimizing the competence of their existing compensatory postural control strategies.

Recurrence Quantification Analysis of Human Postural Fluctuations in Older Fallers and Non-fallers

We investigate postural sway data dynamics in older adult fallers and non-fallers. Center of pressure (COP) signals were recorded during quiet standing in 28 older adults. The subjects were divided in two groups: with and without history of falls. COP time series were analyzed using recurrence quantification analysis (RQA) in both anteroposterior and mediolateral (ML) directions. Classical stabilometric variables (path length and range) were also computed. The results showed that RQA outputs quantifying predictability of COP fluctuations and Shannon entropy of recurrence plot diagonal line length distribution, were significantly higher in fallers, only for ML direction. In addition, the range of ML COP signals was also significantly higher in fallers. This result is in accordance with some findings of the literature and could be interpreted as an increased hip strategy in fallers. The RQA results seem coherent with the theory of loss of complexity with aging and disease. Our results suggest that RQA is a promising approach for the investigation of COP fluctuations in a frail population.

Зв’язок між м’язовою активністю та кінематикою нижньої кінцівки в повільних рухах присідання людини

Squatting can be performed on ankle strategy when ankle joint is flexed more than a hip joint and on hip strategy when large changes occur at the hip joint. The relationships between changes ofjoint angles and electromyogram (EMG) of the leg muscles were studied in five healthy men during squatting that was performed at the ankle and hip strategies with a slow changes in the knee angle of 40 and 60 degrees. It is established that at ankle strategy the ankle muscles were activated ahead of joint angle changes and shifting the center of pressure (CT) on stabilographic platform, whereas activation of the thigh muscles began simultaneously with the change of the joint angles, showing the clear adaptation in successive trials and a linear relationships between the static EMG component and the angle changes of the ankle joint. In the case of hip strategy of squatting the thigh muscles were activated simultaneously with the change in the joint angles and the displacement of CT, whereas the ankle muscles were activated later than the thigh muscles, especially the muscle tibialis anterior, showing some adaptations in consecutive attempts. At the ankle strategy the EMG amplitude was greatest in thigh muscles, reproducing contour of changes in joint angles, whereas the ankle muscles were activated only slightly during changes of joint angles. In the case of hip strategy dominated the EMG amplitude of the muscle tibialis anterior, which was activated when driving down the trunk and fixation of the joint angles that was accompanied by a slight coactivation of the calf muscles with the step-like increase in the amplitude of the EMG of the thigh muscles. Choice of leg muscles to start the squatting on both strategies occurred without a definite pattern, which may indicate the existence of a wide range of options for muscle activity in a single strategy.

Intersegmental Moment Analysis Characterizes the Partial Correspondence of Jumping and Jerking

The aim of this study was to quantify internal joint moments of the lower limb during vertical jumping and the weightlifting jerk to improve awareness of the control strategies and correspondence between these activities, and to facilitate understanding of the likely transfer of training effects. Athletic men completed maximal unloaded vertical jumps (n = 12) and explosive push jerks at 40 kg (n = 9). Kinematic data were collected using optical motion tracking and kinetic data via a force plate, both at 200 Hz. Joint moments were calculated using a previously described biomechanical model of the right lower limb. Peak moment results highlighted that sagittal plane control strategies differed between jumping and jerking (p < 0.05) with jerking being a knee dominant task in terms of peak moments as opposed to a more balanced knee and hip strategy in jumping and landing. Jumping and jerking exhibited proximal to distal joint involvement and landing was typically reversed. High variability was seen in nonsagittal moments at the hip and knee. Significant correlations were seen between jump height and hip and knee moments in jumping (p < 0.05). Although hip and knee moments were correlated between jumping and jerking (p < 0.05), joint moments in the jerk were not significantly correlated to jump height (p > 0.05) possibly indicating a limit to the direct transferability of jerk performance to jumping. Ankle joint moments were poorly related to jump performance (p > 0.05). Peak knee and hip moment generating capacity are important to vertical jump performance. The jerk appears to offer an effective strategy to overload joint moment generation in the knee relative to jumping. However, an absence of hip involvement would appear to make it a general, rather than specific, training modality in relation to jumping.

Biomechanical and Proprioceptive Differences during Drop Landings between Dancers and Non-dancers

The focus of this research was to determine if female dancers have differing kinematic and kinetic characteristics when landing from three heights (0.2, 0.5, and 0.8 m) both with and without vision compared to non-dancers. It was hypothesized that dancers would show differing kinematic and kinetic patterns of control due to their increased proprioceptive awareness. Eight collegiate dancers and seven collegiate controls who were neither dancers nor collegiate jumping athletes volunteered for this study. Sagittal plane lower limb joint angles were measured at 100 Hz prior to landing through stability with a high-speed camera, and peak vertical ground reaction forces relative to body weight were recorded with an indwelling force plate. Results indicated biomechanical differences across height and vision conditions, as well as between groups. Kinetic results showed a significant height effect with respect to vertical ground reaction forces. From the 0.8 m drop, both dancers and non-dancers produced significantly greater ground reaction forces when landing without vision compared to when they landed with vision. No significant kinetic differences were found between groups. Kinematic results revealed a significant height effect for the hip and knee angles across groups and vision conditions, meaning that as drop height increased, the participants demonstrated greater range of motion in their hip and knee joints. Dancers and non-dancers responded differently when dropping from 0.8 m without vision. Dancers significantly increased hip flexion compared to landing with vision, while non-dancers tended to stiffen up and reduced hip flexion. These findings suggest that dancers utilize proprioceptive input more effectively as they adopted a hip strategy (flexion of the hips) to maintain stability. Training dancers without vision may impact dance instruction and reduce the risk of injuries when landing.

Diabetic patients with and without peripheral neuropathy reveal different hip and ankle biomechanical strategies during stair descent

The progression of diabetes and the challenge of daily tasks may result in changes in biomechanical strategies. Descending stairs is a common task that patients have to deal with, however it still has not been properly studied in this population. We describe and compare the net joint moments and kinematics of the lower limbs in diabetic individuals with and without peripheral neuropathy and healthy controls during stair descent. Forty-two adults were assessed: control group (13), diabetic group (14), and neuropathic diabetic group (15). The flexor and extensor net moment peaks and joint angles of the hip, knee, and ankle were described and compared in terms of effect size and ANOVAs (p<0.05). Both diabetic groups presented greater dorsiflexion [large effect size] and a smaller hip extensor moment [large effect size] in the weight acceptance phase. In the propulsion phase, diabetics with and without neuropathy showed a greater hip flexor moment [large effect size] and smaller ankle extension [large effect size]. Diabetic patients, even without neuropathy, revealed poor eccentric control in the weight acceptance phase, and in the propulsion phase, they showed a different hip strategy, where they chose to take the leg off the ground using more flexion torque at the hip instead of using a proper ankle extension function.

Postural responses during volitional and perturbed dynamic balance tasks in new lower limb amputees: A longitudinal study

This study examined the adaptation of postural responses in transtibial amputees during both perturbed and volitional dynamic balance tasks during a five-month period following discharge from inpatient rehabilitation. Seven unilateral transtibial amputees performed the sensory organisation test (SOT) and the limits of stability (LOS) test protocols on the NeuroCom Equitest® at one, three and six months post-discharge from in-patient rehabilitation. Overall balance ability improved significantly (p=0.01) following discharge as did utilisation of somatosensory input (p=0.01), with hip strategy use decreasing. Reaction time and movement velocity did not change significantly in the majority of target directions for the LOS test. However, endpoint COG excursion and directional control were significantly increased in a number of directions (p≤0.05). Although balance ability improved following discharge from rehabilitation, participants were heavily reliant upon vision in order to maintain balance. Following discharge from rehabilitation, amputees were seemingly able to increase the spatial and accuracy aspects of volitional exploration of their LOS. However, temporal aspects did not display any adaptation, suggesting a trade-off between these aspects of postural control. Further practice of performing volitional postural movements under increasing time pressure, for example using low-cost gaming tools, may improve balance ability and postural control.

OPTIMIZATION-BASED DYNAMIC PREDICTION OF HUMAN POSTURAL RESPONSE UNDER TILTING OF BASE OF SUPPORT

The purpose of this paper is to study formulations and computational procedures for prediction of natural human response to tilting of its base of support. The human skeletal structure is modeled as a five-segment, four-degree-of-freedom mechanical system standing on sinusoidally driven tilting platform in the sagittal plane. The problem is formulated based on predictive dynamics method that leads to an optimization problem. The joint torque square is included in the performance measure and the dynamic stability is achieved by satisfying the vertical forces criterion. The constrained nonlinear optimization problem is solved using an algorithm based on the sequential quadratic programming (SQP) approach. The results which are joint trajectories and torques are characterized in terms of two main types of movement strategies observed in humans, namely, the ankle and hip strategies. Moreover, the effect of arms on the stability of the model is studied. The results obtained with the formulation are validated with the experimental data. Simulation results demonstrate the effectiveness of the proposed formulation in prediction of natural motion of human in response to tilting of the base plate.

Stair ascent kinematics and kinetics with a powered lower leg system following transtibial amputation

During stair ascent (STA) persons with transtibial amputation (TTA) typically adopt a hip strategy to compensate for the limited ankle motion and joint power that is characteristic of conventional energy storing and returning (ESR) prosthetic feet. The purpose of this investigation was to determine if providing ankle power via a powered prosthetic device (BiOM) normalized STA kinematics and kinetics. Eleven individuals with TTA participated in two STA gait analysis sessions: (1) using an ESR foot, and (2) using the BiOM. Eleven height and weight matched able-bodied controls (CONT) were also assessed. Lower extremity peak kinematic and kinetic values were calculated at a self-selected and controlled cadence (80steps/min). Increased prosthetic limb peak ankle plantarflexion and push-up power were observed while using the BiOM as compared to ESR. Peak ankle power was not significantly different between BiOM and CONT indicating normalization of ankle power generation. However, peak ankle plantarflexion was significantly lower than CONT. Limb asymmetries including greater prosthetic limb hip flexion and power during stance, and decreased prosthetic limb knee power during stance were observed in the BiOM and ESR conditions. The results suggest that the BiOM successfully increased ankle motion and restored ankle power during STA. These differences did not, however, reduce the use of a hip strategy while ascending stairs. Additional device specific training may be necessary to utilize the full benefits of the device.

HUMANOID FALL AVOIDANCE USING A MIXTURE OF STRATEGIES

If we are to one day rely on robots as assistive devices they should be capable of mitigating the impact of random disturbances and avoid falling. Humans are surprisingly apt at remaining on their feet when pushed; they rely on reflexes such as bending the ankles and/or the hips, or by taking a step if the magnitude of the disturbance is relatively large. This paper presents a fall avoidance scheme that is capable of applying both ankle and hip strategies on a humanoid robot. While both strategies serve the same purpose, the hip strategy can absorb larger disturbances but has a higher energy overhead and should be avoided when it is not necessary. Our system is capable of detecting at the onset of a disturbance if an ankle or hip strategy is more appropriate. The decision is taken based on a 'decision surface' that is delimited by threshold values of the robot's state variables. The control is based on the Virtual Model Control (VMC) approach. The system is tested on a simulated robot developed under Gazebo as well as on a real small-scale humanoid robot. Results show successful fall avoidance with an ability to choose the optimum fall avoidance strategy.

Assessment of balance in unsupported standing with elderly inpatients by force plate and accelerometers

Unsupported standing is one of the most important functional tasks involving balance control. Unlike younger people, who have been shown to counteract imbalance preferably with an ankle strategy, older people tend to do so with a hip strategy. These strategies can be described by matching balance measures at floor and hip level, a good match representing an ankle-dominant strategy and a low one a hip-dominant strategy. The aim of this study was to show possible change in the association between force platform measurement at floor level and accelerometry at hip level in elderly inpatients standing unsupported during rehabilitation. Forty four elderly inpatients (mean age 82.5 yrs) after hip fracture or stroke were recruited for the study. Balance was assessed after admission and 2 weeks later on a force platform at floor level and simultaneously by a tri-axial accelerometer at hip level. The correlation between the 2 measures was initially poor to fair (r=0.04 to r=0.51), but increased after 2 weeks of rehabilitation (r=0.30 to r=0.66). A change in the association between measures obtained at lower back level and floor level may indicate a change from a hip- to an ankle-dominant strategy, to counteract imbalance during unsupported standing.

Altered postural control strategies and sensory organization in children with developmental coordination disorder

The postural control of children with and without developmental coordination disorder (DCD) was compared under conditions of reduced or conflicting sensory input. Twenty-two children with DCD (16 males, 6 females; mean age 7years 6months, SD 1year 5months) and 19 children with normal motor development were tested (13 males, 6 females; mean age 6years 11months, SD 1year 1month). Standing balance, sensory organization and motor control strategy were evaluated using the sensory organization test (SOT). The results revealed that children with DCD had lower composite equilibrium scores (p<.001), visual ratios (p=.005) and vestibular ratios (p=.002) than normal children in the control group. No significant between-group difference in their average somatosensory ratio was observed. Additionally, children with DCD had lower motor strategy scores (swayed more on their hips) than the normal children when forced to depend on vestibular cues alone to balance (p<.05). We conclude that children with DCD had deficits in standing balance control in conditions that included reduced or conflicting sensory signals. The visual and vestibular systems tended to be more involved in contributing to the balance deficits than the somatosensory system. Moreover, children with DCD tended to use hip strategy excessively when forced to rely primarily on vestibular signals to maintain postural stability.

The effect of Functional Electric Stimulation in stroke patients' motor control – a case report

Functional Electric Stimulation (FES) has been studied as a therapeutic resource to reduce spasticity in hemiplegic patients, however there are no studies about the effects of FES in motor control of these patients during functional tasks like balance maintenance. Muscular activation of gastrocnemius medialis and semitendinosus was investigated in both limbs of a hemiparetic patient during self-disturbed quiet stance before and after FES on tibialis anterior, by surface electromyography. The instant of maximum activation peak of GM and ST were calculated immediately after a motor self-disturbance, in order to observe muscular synergy between these two muscles, and possible balance strategies used (ankle or hip strategy). At the preserved limb there occurred distal-proximal synergy (GM followed by ST), expected for small perturbations; however, at spastic limb there was inversion of this synergy (proximal-distal) after FES. It is possible that intervention of electricity had inhibited synergical pathways due to antidromic effect, making it difficult to use ankle strategy in the spastic limb.