Sungjae Hwang

University of Maryland Eastern Shore | UMES · Kinesiology

Purpose: To investigate foot and ankle somatosensory function in children with cerebral palsy (CP). Methods: Ten children with spastic diplegia (age 15 ± 5 y; GMFCS I-III) and 11 typically developing (TD) peers (age 15 ± 10 y) participated in the study. Light touch pressure and two-point discrimination were assessed on the plantar side of the fo...

Background Stochastic Resonance (SR) Stimulation has been used to enhance balance in populations with sensory deficits by improving the detection and transmission of afferent information. Despite the potential promise of SR in improving postural control, its use in individuals with cerebral palsy (CP) is novel. The objective of this study was to in...

Current thinking views mild head impact (i.e., subconcussion) as an under-recognized phenomenon that has the ability to cause significant current and future detrimental neurological effects. However, repeated mild impacts to the head often display no observable behavioral deficits based on standard clinical tests, which may lack sensitivity. The cu...

Parkinson's disease (PD) is a progressive degenerative disease manifested by tremor, rigidity, bradykinesia, and postural instability. Deficits in proprioceptive integration are prevalent in individuals with PD, even at early stages of the disease. These deficits have been demonstrated primarily during investigations of reaching. Here, we investiga...

A robotic gait training system includes a femoral support unit supporting a thigh of a patient, a hip joint support unit supporting buttocks of the patients, a lower leg support unit supporting a lower leg, an ankle support unit supporting an ankle, a support fixing toe tip positioned at an ankle height of the patient in use, a toe tip pad supporti...

Maintaining upright bipedal posture requires a control system that continually adapts to changing environmental conditions, such as different support surfaces. Behavioral changes associated with different support surfaces, such as the predominance of an ankle or hip strategy, is considered to reflect a change in the control strategy. However, traci...

PURPOSE: The purpose of this study was to determine if an app with specific visual acuity requirements can identify changes in walking from a single task condition to a dual task condition with. BACKGROUNDS/SIGNIFICANCE: It is well known that dual tasking has a negative impact on walking behavior. Gait speed slows down ~15% when talking on a cell...

We simultaneously perturbed visual, vestibular and proprioceptive modalities to understand how sensory feedback is re-weighted so that overall feedback remains suited to stabilizing upright stance. Ten healthy young subjects received an 80 Hz vibratory stimulus to their bilateral Achilles tendons (stimulus turns on-off at 0.28 Hz), a ±1 mA binaural...

The excessive accumulation of physical burden is known widely as one of the main factors underlying musculoskeletal disorders in the working population. The current study was performed to evaluate the loads imposed on the muscles and joints by excessive accumulation of physical burdens for the estimation of a potentiality of musculoskeletal disorde...

We developed an active ankle-foot orthosis AAFO that controls dorsiflexion/plantarflexion of the ankle joint to prevent foot drop and toe drag during hemiplegic walking. To prevent foot slap after initial contact, the ankle joint must remain active to minimize forefoot collision against the ground. During late stance, the ankle joint must also rema...

The general static optimisation (GSO) process is one of various muscle force estimation methods due to its low computational requirements. However, it can show biased muscle force estimation under muscle co-contraction. In the present study, we introduced a novel hybrid static optimisation (HSO) method to estimate reasonable muscle forces during mu...

We developed an active ankle-foot orthosis (AAFO) that controls dorsiflexion/plantarflexion of the ankle joint to prevent foot drop and toe drag during hemiplegic walking. To prevent foot slap after initial contact, the ankle joint must remain active to minimize forefoot collision against the ground. During late stance, the ankle joint must also re...

In this study, the circular friction massage technique was performed on the trapezius, the levator scapulae, and the deltoid muscles to collect the information on massage pressures and positions, and thus to utilize it in professional massage system design. Massage motion was measured with the 3-D motion capture system and finger pressures were sim...

Information about muscle forces helps us to understand human movements more completely. Recently, studies on estimating muscle forces in real-time have been directed forward; however, the previous studies have some limitations in terms of using a three-dimensional (3D) motion capture system to obtain human movements. In the present study, an electr...

Information about muscle forces helps us to understand human movements more completely. Recently, studies on estimating muscle forces in real-time have been directed forward; however, the previous studies have some limitations in terms of using a three-dimensional (3D) motion capture system to obtain human movements. In the present study, an electr...

The presented study highlights the feasibility and accuracy of novel computational methods based on a morphological filter and a least square acceleration filter to detect step events for evaluating normal and pathological gait parameters using a single accelerometer. This is the first evidence that demonstrates the feasibility and accuracy of the...

Gait, a method of locomotion, is a process that an animal moves itself from one position to another. The human gait serves an individual’s basic need to move from place to place. As such, the gait is the most common in all human movements. It also can provide independence and in the many activities of daily life. The importance of gait as an abilit...

In this study, an EMG-driven model was developed, and isometric and isokinetic contraction movements were evaluated to validate the developed model. One healthy male participated in this study. The dynamometer tasks were performed for maximum voluntary isometric contractions (MVIC) for ankle dorsiflexor and plantarflexor, isokinetic contraction at...

Estimation of muscle forces is important in biomechanics, therefore many researchers have tried to build a muscle model. Recently, optimization techniques for adjustingmuscle parameters, i.e. EMG-drivenmodel, have been used to estimatemuscle forces and predict joint moments. In this study, an EMG-driven model based on the previous studies has been...

Gait initiation is a transitional process from the balanced upright standing to the beginning of steady-야 ate walking. Dysbalanced g빠 initiation Of1않n causes stroke patients to fall. The net center of pressure, measured by two triaxial force plates from twenty healthy subjects and two stroke patients, was investig와 ed to assess asyrnmeσY of gait in...

Electrical stimulation (ES) can be used to correct foot drop and toe drag during hemiplegic walking. This study designed to make potable electrical stimulation system according to correct foot drop of hemiplegic walking. A right hemiplegic patient was participated and electrical stimulator was mounted on the motor point of the tibialis anterior (TA...

The purpose of this study was to assess activation and contribution of muscles of the elderly according to increased loading during the arm flexion extension resistance exercise. Surface electromyographic signals were acquired from biceps brachii, triceps brachii, deltoid posterior, pectoralis major and latissimmus dorsi to determine the difference...

In this study, we analyzed the elderly joint movements and changes in muscle length during STS at various sitting heights through the motion analysis and the muscu-loskeletal modeling. Five elderly and five young were participated in this experiment. Three heights of sitting posture which could represent typical sitting in Korean daily life were ch...

This paper suggests the novel algorithm for the estimating gait parameters of the hemiplegic patients using a 3-axis accelerometer. The signal processing for algorithm consists of a bandpass filter and a least square acceleration filter. To evaluate the performance of the algorithm, the correlation coefficients of the stride and the step time betwe...

Lumbar lordosis is defined as the anterior convexity of the lumbar spine in the sagittal plane. Its degree is variable between individuals, affected many other factors. Clinical methods to define lumbar lordosis are Cobb’s angle measurement and the angle between extension line of boundary of the first and fifth vertebral body. In this study, the lo...

Gait phase detection is important for evaluating the recovering of gait ability in patients with paralysis as well as for determination of stimulation in FES walking. Forceplate in three dimensional system can give the most objective and accurate information about gait phase detection, however it is very expensive and limited in restricted area of...

In this study, we have developed a novel step detection algorithm for gait evaluation of patients with hemiplegia based on trunk accelerometry device. For this, we have used a bandpass filter and a least square acceleration (LSA) filter which is characterized by emphasizing the peak or valley point of the acceleration signals for each 3-axis accele...

Falls are one of the main concerns of the elderly. Proper postural adjustments to maintain balance involve the activation of appropriate muscles to produce force and to relocate the center of body mass (CoM). In this study, biomechanical aspects of dynamic postural responses against forward perturbations were experimentally determined by simultaneo...

Objective: The purpose of this study was to evaluate the validity of masticatory dysfunction questionnaires. Methods: This study consisted of cross-sectional surveys of self-reporting questionnaires and clinical examinations. Information from 398 subjects, aged 60 or more, was selected using cluster sampling. The questionnaires included sociodemo...

Gait initiation is a transitional process from the balanced upright standing to the beginning of steady-state walking. Steady-state walking represents the start of repeated gait pattern with steady-state walking speed within one gait cycle. Hemiplegic patients’ gait initiation was analyzed using the 3D motion analysis system synchronized with 2 for...

Existing therapy and orthosis for upper arm rehabilitaion have some shortcomings such that orthosis can’t help patient’s motion but it just supply, patient has to go to hospital for therapy and patient can’t reflect his will in therapy. Because of these reasons, upper arm rehabilitaion system was developed, which could increase hemiplegic patient’s...

Lumbar lordosis is defined as the anterior convexity of the lumbar spine in the sagittal plane. Its degree is variable between individuals, affected many other factors. Clinical methods to define lumbar lordosis are Cobb’s angle measurement and the angle between extension line of boundary of the first and fifth vertebral body. In this study, the lo...

In this study, treadmill walking and overground walking were compared at the same condition based on kinematics and energy expenditures(EE). In addition, we compared the actual energy expenditure and calculated EE by treadmill. The kinematics of treadmill and overground walking were very similar. The values at each joint were significantly differen...

The purpose of this study was to compare the muscle length and muscle force from developed model and commercial software. Basically a Hill-type muscle model consists of springs and damper, and thus muscle force was changed by muscle length. Because of this reason, the researchers needed to know the changes in muscle length and developed algorithm t...

In this study, we developed a robotic gait trainer which induces the gait training based on predefined continuous proper lower extremity joint movements for the paralysis. AC servo motors and linear actuators were used to control hip and knee joints of patients and the weight support system was used to support the patient's weight during the gait t...

In this study, an ideal electromechanical KAFO, satisfying stability in the stance and knee flexion in the swing phase during walking, was developed. Biomechanical evaluations were performed on four polio patients by means of three-dimensional gait analyses and energy consumption studies. From the three-dimensional gait analysis on poliomyelitis pa...

Sit to stand(STS) movement is one of the most common activity in daily life. In addition, Korean traditionally stand up from various sitting heights in one's daily life compared to other foreigners. As Korea enter rapidly to the aging society, needs of the elderly's independent life are increasing. Therefore the importance of research about the ana...

Many studies have been unsuccessful to classify biomechanical characteristics in pathological gaits of hemiplegic patients using joint motions of the lower extremity. In this paper, we analyzed nondestructively changes in joint movements and the muscle length of lower limbs during hemiplegic walking by 3D motion analysis and musculoskeletal modelin...

In this study, we analyzed the effect of the walking with the developed AAFO for a hemiplegic patient. Results showed that the AAFO could prevent not only foot drop by the proper plantarflexion during loading response but also toe drag by sufficient amount of plantarflexion in pre-swing and reasonable dorsiflexion during swing phase, enhancing all...

In this study, joint moments, support moments and lumbar lordosis were investigated for two different symmetrical lifting techniques using the three-dimensional motion analysis: squat and stoop. Thirteen male volunteers lifted boxes weighing 5, 10 and 15kg by both squat and stoop lifting techniques. There were no significant differences in maximum...

The hemiplegic gait is characterized by the slow speed, the short step length and the increased energy consumption, due to drop the foot and to drag toes. In this study, we developed an active ankle-foot orthosis(AAFO) which could control dorsiflexion/plantarflexion of the ankle joint to prevent dropping the foot and dragging toes during walking fo...

In the present study, knee varus torque and mediolateral accelerations were compared using the threedimensional motion analysis system and a linear accelerometer in order to determine biomechanical effects of heel wedges during walking. Wedges were inclined with 10° and 15° in medial and lateral directions respectively. Both knee varus torques and...

In this paper, biomechanical aspects of dynamic postural responses against forward perturbations were experimentally determined by simultaneous measurements of joint angles, linear accelerations, EMG activations, CoP movements and ground reaction forces(GRF). The sequence of joint motions due to the forward perturabation was in the order of ankle d...

In this study, contributions of lower extremity joints and lumbar lordotic angles were investigated for two different symmetrical lifting techniques using the three-dimensional motion analysis: squat and stoop. Joint angles and moments were determined when the lumbar curvature changed from kyphosis to lordosis. Thirteen male volunteers lifted boxes...

Many studies have been unsuccessful to classify biomechanical characteristics of pathological gaits in hemiplegic patients using joint motions of the lower extremity. In this paper, we analyzed changes in muscle length of lower limbs for hemiplegic walking by using the 3D motion analysis and the musculoskeletal modeling to determine gait patterns....

In this study, we developed an active ankle-foot orthosis(AAFO) which can control dorsi/ plantar flexion of the ankle joint to prevent foot drop and toe drag during walking. 3D gait analyses were performed on five healthy subjects under three different gait conditions: the normal gait without AFO, the SAFO gait with the conventional plastic AFO, an...

In this study, we analyzed joint moments during the symmetrical lifting in two different postures, using the three-dimensional motion analysis. Boxes weighing 5, 10 and 15kg were lifted by both squat and stoop techniques. The ankle moment in stoop was always larger than that in squat and the support moment was the largest at the end of the lifting...

In this study, we developed an active ankle-foot orthosis (AAFO) which can control the dorsi/ plantarflexion of the ankle joint to prevent foot drop and toe drag during walking. To prevent slapping foot after heel strike, ankle joint has to be controlled actively to minimize fore foot collision with the ground. In the late stance, ankle joint also...

In this study, we developed an active ankle-foot orthosis (AAFO) which could control dorsiflexion/plantarflexion of the ankle joint to prevent foot drop and toe drag during walking. To prevent foot slap after initial contact, the ankle joint needs to be actively controlled to minimize forefoot collision with the ground. During late stance, the ankl...

In this study, we analyzed the plantar shear stress and normal pressure in lateral heel diabetic foot patients during walking by using in-shoe local shear stress and plantar pressure measurement systems. The shear force transducer based on the magnetic-resistive principle, was a rigid 3-layer circular disc. Shear transducers were mounted on the loc...

The present study investigated the biomechanical effects of weight variation for side loaded carriage during walking upon joint moments and the center of body mass by using the inverse dynamic analysis. The motion data which were used as input data for inverse dynamic simulation were measured by the 3D motion analysis system. Six infrared cameras a...

In this study, we determined joint moments and muscle forces in the lower extremity during walking with different heel-height shoes using the 3D motion analysis and the corresponding musculoskeletal modeling. Totally fifteen healthy women participated in the 3D motion analysis for various walking with barefoot, flat shoe, 3cm, 6cm and 9cm high heel...

The purpose of this study is to quantitatively evaluate foot motions in the normal and hallux valgus(HV) patients using a proposed multi-segment foot model. Results showed that HV patients exhibited relatively smaller flexion/extension, especially in terminal stance. An early abduction at the ankle during terminal stance was also noted in HV patien...

Pressure distributions on the buttocks and thighs by the functional electrical stimulation on the gluteus maximus, sartorius and hamstring in the seating posture were analyzed for ten healthy young volunteers in order to determine which muscle can be stimulated for pressure ulcer prevention. Muscles were stimulated every 5 seconds over 30 seconds b...

Pressure distributions on the buttocks and thighs by the functional electrical stimulation on the gluteus maximus, sartorius and hamstring in the seating posture were analyzed for ten healthy young volunteers in order to determine which muscle can be stimulated for pressure ulcer prevention. Muscles were stimulated every 5 seconds over 30 seconds b...

The purpose of this study is to quantitatively evaluate foot motions in the normal and hallux valgus(HV) patients using a proposed multi-segment foot model. Results showed that HV patients exhibited relatively smaller flexion/extension, especially in terminal stance. An early abduction at the ankle during terminal stance was also noted in HV patien...

Pressure ulcer is the injury state by continuous normal or shear stress on the skin for spinal cord injury(SCI) patients. Even though functional electrical stimulation recently receives much attention as a promising method for the pressure ulcer prevention in plegic patients or elderly people, its protocol has not been developed yet. In order to de...

In these days, various foot problems have been rapidly increasing. Hallux valgus(HV), one of the most popular foot diseases, is found especially in mid-aged women. The most common cause of HV is to wear with small and pointed shoes for a long time. If HV is left untreated, the deformity in the other regions of the foot also follows. Even though man...

In this study, we determined joint moments and muscle forces in the lower extremity during walking with different heel-height shoes using the 3D motion analysis and the corresponding musculoskeletal modeling. Totally fifteen healthy women participated in 3D motion analysis for various walking with barefoot, flat shoe, 3cm, 6cm and 9cm high heels. I...

This study investigated biomechanical effects on the body center of mass(COM) and joint moments of lower extremity as the weight of sided load in walking. Also the present study showed correlation between body center of mass and joint moments. The motion data used as input data for inverse dynamic simulation were measured by the 3D motion analysis...

ARelative contributions of lower extremity joints on the support moment were investigated in this study Three-dimensional gait analyses were performed in normal walking and in unexpected step-down walking For both gait studies, inverse dynamics were performed to obtain each joint moment of the lower extremity, which was applied to the forward dynam...

INTRODUCTION The generation of the forward movement and the stable support of the upper body are two important roles of the lower limb in walking [1]. The function of the body support has been recently received much attention. The concept of the support moment, defined as the sum of all joint moments in the lower limb, has been used to determine th...

Falling which is frequently resulting in serious physical injuries is an important problem in the elderly. The unexpected walking is one of the most credible causes of falling in the elderly. In this paper, we investigated the relative contributions of lower extremity joints on the support moment in unexpected step-down walking using the forward dy...