Shu-Zon Lou

Effects of the type and direction of support surface perturbation on postural responses

BackgroundPostural control is organized around a task goal. The two most frequently used types of tasks for postural control research are translational (translation along the anterior-posterior axis) and rotational (rotation in sagittal plane) surface perturbations. These types of perturbations rotate the ankle joint, causing different magnitudes and directions of body sway. The purpose of this study was to investigate the effects of the type (translation vs. rotation) and direction (forward/toe up vs. backward/toe down) of the perturbation on postural responses.MethodNineteen healthy subjects were tested with four perturbations, i.e., forward and backward translation and toe up and toe down rotation. The onset latency and magnitude of muscle activations, angular changes, and COM displacements were measured. In addition, the kinematic data were divided into two phases. The initial phase reflected the balance disturbance induced by the platform movement, and the reversal phase reflected the balance reaction.ResultsThe results showed that, in the initial phase, rotational perturbation induced earlier ankle movement and faster and larger vertical COM displacement, while translational and forward/toe up perturbations induced larger head and trunk angular change and faster and larger horizontal COM displacement. In the reversal phase, balance reaction was attained by multi-joint movements. Translational and forward/toe up perturbations that induced larger upper body instability evoked faster muscle activation as well as faster and larger hip or knee joint movements.ConclusionsThese findings provide insights into an appropriate support surface perturbation for the evaluation and training of balance.

Effect of various forearm axially rotated postures on elbow load and elbow flexion angle in one-armed arrest of a forward fall

BACKGROUND Falling onto the outstretched hand is a major cause of upper extremity injury. The overall objectives of this study were to develop an experimental model for elbow load during a simulated fall onto one-armed arrest using three different forearm axially rotated postures as alternative fall arrest strategies. Additionally, the relationship between the elbow flexion angle and different axially rotated postures were also investigated. METHODS Fifteen healthy young male Taiwanese graduate students with an average age of 23 years were studied. Subjects performed a one-armed arrest of a 5 cm fall onto a force plate. Each subject fell onto the force plate with his forearm 45 degrees axial externally rotated (ER), non-rotated (NR), and 45 degrees axial internally rotated (IR) postures. Kinematics and kinetics of the upper extremity were calculated and analyzed by using laboratory-developed motion analysis procedures. FINDINGS The valgus-varus shear forces in the ER group were 1.4 times greater than the NR group, and 2.7 times greater than the IR group. The elbow joint remained at almost full extension in the ER (3.9 degrees) group, while elbow flexion angle was observed in the NR (24.6 degrees) and IR (40.3 degrees) groups. INTERPRETATION A fall onto the outstretched hand with an externally rotated forearm should be avoided in order to reduce excessive valgus-varus shear force on the elbow joint. Knowledge of elbow kinematics and kinetics during a forward fall with various forearm axially rotated posture may be helpful in preventing injuries.

Effects and after-effects of voluntary intermittent light finger touch on body sway

Effects of light touch on body sway have usually been investigated with some form of constant contact. Only two studies investigated transient sway dynamics following the addition or withdrawal of light touch. This study adopted a paradigm of intermittent touch and assessed body sway during as well as following short periods of touch of varying durations to investigate whether effects and after-effects of touch differ as a function of touch duration. In a modified heel-to-toe posture, 15 blindfolded participants alternated their index finger position between no-touching and touching on a strain gauge in response to low- and high-pitched auditory cues. Five trials of 46 s duration were segmented into 11 sections: a 6-s no-touching period was followed by five pseudo-randomly ordered touching periods of 0.5-, 1-, 1.5-, 2-, and 5-s duration, each of which was followed by another 6-s no-touching interval. Consistent with previous research, compared to no-touching intervals sway was reduced during touch periods with touch durations greater than 2 s. Progressive reductions in sway were evident after touch onset. After touch withdrawal in the 2-s touch condition, postural sway increased and returned to baseline level nearly immediately. Interestingly, in the 5-s touch condition, reductions in sway persisted even after touch withdrawal in the medio-lateral and antero-posterior plane for around 2.5 s and 5.5 s, respectively. Our intermittent touch paradigm resulted in duration-dependent touch effects and after-effects; the latter is a novel finding and may result from a more persistent postural set involved in proactive sway control.

User Satisfaction with Orthotic Devices and Service in Taiwan

User satisfaction is afforded considerable importance as an outcome measurement in evidence-based healthcare and the client-centered approach. Several studies have investigated user satisfaction with orthoses. Few studies have investigated user satisfaction with orthoses in Taiwan. Therefore, the purpose of this study was to investigate the user satisfaction with orthotic devices and service using the Taiwanese version of Quebec User Evaluation of Satisfaction with Assistive Technology. We conducted a cross-sectional study of 280 subjects who had used orthoses and received services. The results showed that the mean satisfaction score was 3.74 for the devices and 3.56 for service. Concerning the participants, 69.1% and 59.6% were quite satisfied or very satisfied with their devices and service, respectively. The satisfaction score of orthotic service was lower than that of the devices. Regarding demographic characteristics, participants living in different areas differed only in service score (p = 0.002). The participants living in eastern area and offshore islands were the least satisfied with the orthotic service. For clinical characteristics, there was a significant difference in satisfaction scores among severity of disability (all p = 0.015), types of orthoses (all p = 0.001), and duration of usage (all p = 0.001). The participants with mild disability, wearing the pressure garment and using the orthosis for less than one year, were the most satisfied with their orthotic devices and service. There is a need for improved orthotic devices and services, especially with respect to the comfort of the devices and the provision of subsidy funding.

Effect of forearm axially rotated posture on shoulder load and shoulder abduction / flexion angles in one-armed arrest of forward falls

BACKGROUND Falling onto the outstretched hand is the most common cause of upper extremity injury. This study develops an experimental model for evaluating the shoulder load during a simulated forward fall onto one hand with three different forearm axially rotated postures, and examines the shoulder abduction angle and shoulder flexion angle in each case. METHODS Fifteen healthy young male subjects with an average age of 23.7 years performed a series of one-armed arrests from a height of 5 cm onto a force plate. The kinematics and kinetics of the upper extremity were analyzed for three different forearm postures, namely 45° externally rotated, non-rotated, and 45° internally rotated. FINDINGS The shoulder joint load and shoulder abduction/flexion angles were significantly dependent on the rotational posture of the forearm. The shoulder medio-lateral shear forces in the externally rotated group were found to be 1.61 and 2.94 times higher than those in the non-rotated and internally rotated groups, respectively. The shoulder flexion angles in the externally rotated, non-rotated and internally rotated groups were 0.6°, 8.0° and 19.2°, respectively, while the corresponding shoulder abduction angles were 6.1°, 34.1° and 46.3°, respectively. INTERPRETATION In falls onto the outstretched hand, an externally rotated forearm posture should be avoided in order to reduce the medio-lateral shear force acting on the shoulder joint. In falls of this type, a 45° internally rotated forearm posture represents the most effective fall strategy in terms of minimizing the risk of upper extremity injuries.

Effects of an Anterior Ankle-Foot Orthosis on Walking Mobility in Stroke Patients: Get Up and Go and Stair Walking

OBJECTIVE To examine the effects of an anterior ankle-foot orthosis (AAFO) on walking mobility in stroke patients. DESIGN Cross-sectional and repeated-measures study design. SETTING A universitys neurologic rehabilitation department. PARTICIPANTS Ambulant stroke patients (N=21). INTERVENTIONS Not applicable. MAIN OUTCOME MEASURES Walking mobility was measured by the Timed Up and Go (TUG) test and the Timed Up and Down Stairs (TUDS) test. The paired t test was used to determine the difference between the mobility performances measured with and without the AAFO. RESULTS There were significant differences between mobility performances with and without an AAFO in the TUG test (P=.038) and the TUDS test (P=.000). CONCLUSIONS This study supports the effect of an AAFO on walking mobility in stroke patients. The findings demonstrate that stroke patients wearing an AAFO may ambulate with greater speed and safety on level surfaces and stairs.

ELBOW LOAD DURING DIFFERENT TYPES OF BENCH-PRESS EXERCISE

The bench press is one of the most popular weight training open-kinetic chain exercise (OKCE) for the upper extremity. Reviewing the literature, there is a very little research regarding the biomechanical analysis of the OKCE of the upper extremity. The purpose of this study is to develop an OKCE testing model of the upper extremity by using the 3D Motion Analysis System. Furthermore, elbow joint loading of two different hand grip position during the bench-press exercise will be investigated. Thirteen male students volunteered for the study. Their average age was 26.1 years, with an average height of 170.6 cm, and an average weight of 70.3 kg. With both hands in neutral position, each subject was asked to perform bench-press type 1 (normal shoulder width), and bench-press type 2 (150% shoulder width). During the type 2 bench-press exercise, there is a significant increase in anterior–posterior and medial–lateral force on the elbow joint loading than the type 1 bench-press exercise. The valgus–varus, flexion–extension moment, and supination–pronation moment of the type 2 bench-press exercise are also greater than the type 1 bench-press exercise. As shown in this study, keeping the distance of both hand grips as shoulder width may reduce the elbow joint loading during bench-press exercise. These data will provide helpful information in clinical rehabilitation and treatment of the upper-extremity injures.

Use of and Self-Perceived Need for Assistive Devices in Individuals with Disabilities in Taiwan

Assistive devices (ADs) can help individuals with disabilities achieve greater independence, and it can enhance the quality of their lives. This study investigated the use of and self-perceived need for ADs in individuals with disabilities, and determined the influence of gender, age as well as type and degree of disability on the use of and self-perceived need for ADs. This descriptive study utilized a cross-sectional survey design with a convenience sample of participants. A total of 1018 subjects with disabilities who visited an exhibition of assistive technology and two ADs research and development centers completed a questionnaires either by themselves or via a caregiver who completed the questionnaire on behalf of the subject or via interviewers trained specifically for this study. The Mann-Whitney U test and Kruskal-Wallis test were used to determine the influence of participant characteristics on the use of ADs. The results showed that 77.2% and 83.3% of the participants reported that they used and needed AD(s) to engage in activities of daily living. The mean quantity of the use of and self-perceived need for total types of ADs were 3.0 and 5.3, respectively. Participants with different disabilities reported different percentages of the use of various types of ADs. No difference was found between genders and among the age groups in the use of quantity of ADs. Individuals with different types and degrees of disability used different quantities of ADs. Participants with physical, visual and multiple disabilities used significantly more ADs compared to participants with intellectual disability. The total quantity of ADs used increased significantly with increased severity of disability. The mean use of assistive devices was lower compared to the mean need of individuals with disabilities. Further study is required to determine why patients feel the need for but not currently use a specific assistive device.

Effect of Anterior Ankle-Foot Orthoses on Weight Shift in Persons With Stroke

OBJECTIVE To examine the effects of an anterior ankle-foot orthosis (AAFO) on the speed and accuracy of weight shift in persons with stroke. DESIGN Cross sectional, repeated measures. SETTING Neurologic rehabilitation department. PARTICIPANTS People with stroke (N=24) who were unable to voluntarily dorsiflex the foot against gravity. INTERVENTION The weight-shift performance was measured with and without the AAFO. MAIN OUTCOME MEASURES The speed and accuracy of sustained and cyclic bilateral weight shift were measured using the computerized dynamic posturography. The movement velocity, maximum excursion, and directional control of sustained weight shift were calculated using the limits of stability test. The on-axis velocity gap, directional control, and stability of cyclic bilateral weight shift were calculated using the rhythmic weight shift test. RESULTS For sustained weight shift, the maximum excursion of weight shift to the affected side was greater with the AAFO (P=.002). For cyclic bilateral weight shift, the on-axis velocity gap in the mediolateral (ML) direction was smaller at a fast speed (P=.004). The stability of the ML and anteroposterior weight shift was higher at slow (P=.002 and P<.001, respectively) and fast (P=.001 and P<.001, respectively) speeds when wearing the AAFO. CONCLUSIONS The findings demonstrated that persons with stroke who wear an AAFO might improve the excursion of the sustained weight shift to the affected side and the speed and stability of cyclic bilateral weight shift in the ML direction.

Postural responses to yaw rotation of support surface

The purposes of this study were to investigate EMG and kinematic responses to yaw rotation of a support surface. Twenty people participated in four conditions, i.e., two velocities (240°/s, 120°/s) and two amplitudes (30°, 15°). Longer latency and smaller muscle responses were induced for yaw rotation, and distal ankle and knee muscles were activated earlier than trunk and neck muscles. Joint kinematics demonstrated larger angular displacements in axial rotation. Velocity and amplitude did not affect onset latency or magnitude of muscle activation but had significant effects on joint movements and COM displacements. Preliminary information about normative data of healthy subjects was obtained, and questions were generated about optimal velocity and amplitude test protocols that require further investigation.